The Pennsylvania State University

The Graduate School

Department of Chemical Engineering

STARCH SPHERULITE PRODUCTION VIA

HIGH TEMPERATURE SPRAY DRYING

A Thesis in

Chemical Engineering

by

Beth Ann Tirio

2009 Beth Ann Tirio

Submitted in Partial Fulfillment of the Requirements

for the Degree of

Master of Science

May 2009

The thesis of Beth Ann Tirio was reviewed and approved* by the following:

Gregory Ziegler Professor of Food Science Thesis Advisor Wayne Curtis Professor of Chemical Engineering Themis Matsoukas Professor of Chemical Engineering Andrew Zydney Professor of Chemical Engineering Head of the Department of Chemical Engineering

*Signatures are on file in the Graduate School

iii

ABSTRACT

This project was undertaken to investigate the production of starch spherulites via high

temperature spray drying. High temperature spray drying is a variation of spray drying in

which the operating feed temperature is above the normal boiling point of the solution. High

temperature spray drying is necessary for starch spherulite production because a starch

dispersion must be heated to at least 160°C, but preferably 180°C, and then cooled at a

moderate rate, 10°C/min to 500°C/min. This allows the starch dispersion to gelatinize on

heating and experience a phase separation into a polymer-rich phase and a solvent-rich

phase on cooling. The polymer-rich phase can then crystallize into a spherulitic morphology.

The elevated maximum temperature requires an operating line pressure of approximately 10

bar prior to atomization to maintain the liquid state of the feed.

An Armfield Tall Form Spray Dryer/Chiller FT 80/81 was modified to be a high

temperature spray drying system which could withstand an operating temperature of 180°C

and an operating pressure of 10 bar. An experiment was designed to determine the effect of

the feed concentration, feed flow rate, operating temperature, and drying temperature on the

total percent recovery, spherulite number density, and spherulite size. In addition, the

percent crystallinity of the spherulites was investigated.

The system was able to successfully produce starch spherulites from 10% w/w, 20%

w/w, and 30% w/w dispersions of high-amylose maize starch in deionized water. There was

extreme variation in the data, however, so no statistically significant relationships between

the design variables and the final product properties could be established. Post hoc analysis

was done to determine the cause of the variation, however, no observable variable yielded a

relationship to the final product properties.

iv

Although no statistically significant relationship could be determined between the operating

conditions and the final product properties, the ability of the high temperature spray system to

produce starch spherulites provides the foundation for future research.

v

TABLE OF CONTENTS

LIST OF FIGURES ................................................................................................................. vii 

LIST OF TABLES ................................................................................................................... ix 

ACKNOWLEDGEMENTS ..................................................................................................... x 

Chapter 1 Motivation and Objectives ..................................................................................... 1 

1.1 Introduction ................................................................................................................ 1 1.2 Motivation .................................................................................................................. 3 1.3 Research Objectives ................................................................................................... 4 

Chapter 2 Literature Review ................................................................................................... 5 

2.1 Summary of Relevant Literature on Starch ................................................................ 5 2.2 Summary of Relevant Literature on Spherulites ........................................................ 11 2.3 Summary of Relevant Literature on Spray Drying .................................................... 19 2.4 Summary .................................................................................................................... 24 

Chapter 3 Materials and Methodolgy...................................................................................... 26 

3.1 Materials ..................................................................................................................... 26 3.2 Sample Preparation .................................................................................................... 31 3.3 Experimental Design .................................................................................................. 32 3.4 Experimental Methodology ........................................................................................ 34 

3.4.1 Spray System Description ............................................................................... 34 3.4.2 Spraying Methodology .................................................................................... 36 

3.5 Data Analysis Methodology ....................................................................................... 37 3.5.1 Light Microscopy ............................................................................................ 37 3.5.2 Percent Recovery ............................................................................................. 38 3.5.3 X-Ray Diffraction ........................................................................................... 39 3.5.4 Differential Scanning Calorimetry .................................................................. 39 

Chapter 4 Results and Discussion ........................................................................................... 41 

4.1 Spray System Design ................................................................................................. 41 4.1.1 Process Modifications ..................................................................................... 41 4.1.2 Design Justification ......................................................................................... 43 

4.2 Spherulite Formation .................................................................................................. 45 4.3 Analysis of Spray Drying Trials ................................................................................ 48 

4.3.1 Percent Recovery Results ................................................................................ 48 4.3.2 Spherulite Size and Number Density .............................................................. 50 4.3.3 Percent Crystallinity ........................................................................................ 53 4.3.4 Differential Scanning Calorimetry .................................................................. 55 

4.4 Supplemental Analysis ............................................................................................... 57 

vi

Chapter 5 Conclusion and Future Work ................................................................................. 59 

5.1 Conclusion ................................................................................................................. 59 5.2 Future Work ............................................................................................................... 61 

Bibliography ............................................................................................................................ 64 

Appendix A Feed Pump Calibration Curve ............................................................................ 69 

Appendix B Effect of Feed Flow Rate and Oil Temperature on Operating Temperature for Water .......................................................................................................................... 70 

Appendix C Differential Scanning Calorimetry Results ......................................................... 72 

Appendix D Hat Design Sketches ........................................................................................... 75 

Appendix E Supplemental Data for Spray Drying Trials ....................................................... 78 

vii

LIST OF FIGURES

Figure 2-1: α-1,4 and α-1,6 glycosidic bonds connecting α-D-glucose units. Reproduced from Eliasson, 2004. ........................................................................................................ 5 

Figure 2-2: Schematic of helical amylose. Reproduced from The Agrana Group, 2007. ........ 7 

Figure 2-3: Schematic of amylopectin with A, B, and C chains labeled. The open circle represents the lone reducing group. Reproduced from Parker and Ring, 2001. ............... 8 

Figure 2-4: (a) – Starch granule schematic showing the alternating amorphous (white) and semi-crystalline (gray) layers. Reproduced from Eliasson, 2004. (b) – The semi-crystalline layer consists of alternating amorphous and crystalline layers due to the non-random placement of the branch points of amylopectin and the double helices of the amylopectin A-chains. Reproduced from Jane, 2006. ................................................ 9 

Figure 2-5: Perspective drawing of a representative 100-residue amylose chain with portions of random, amorphous coil and portions of helices. The helical portions were highlighted by the author. Circles represent glycosidic oxygen and lines are virtual bonds. Reproduced from Jordan, Brant, and Cesaro, 1978. ................................. 11 

Figure 2-6: Starch spherulites under polarized light presented by Creek, 2007. Scale bar is 50 μm. ........................................................................................................................... 12 

Figure 3-1: The drying tower of the Armfield Tall Form Spray Dryer/Chiller FT 80/81 used for this thesis. ........................................................................................................... 27 

Figure 3-2: The modified Armfield Tall Form Spray Dryer/Chiller FT 80/81 used for this thesis. ............................................................................................................................... 28 

Figure 3-3: The feed vessel, feed pump, band heater and controller used with the spray dryer for this thesis. .......................................................................................................... 29 

Figure 3-4: The insulated consecutive dual coil heat exchanger system. ................................ 30 

Figure 3-5: The first of two dual coil heat exchangers used, uncovered. ................................ 31 

Figure 3-6: Process flow diagram of high temperature spray drying system. ......................... 35 

Figure 4-1: The new hat, lower, developed to accommodate the new atomizer. The hat supplied with the spray dyer is in also shown for comparison, upper.............................. 42 

Figure 4-2: New atomizing nozzle by Spraying Systems, Inc (Wheaton, IL). ........................ 43 

Figure 4-3: Operating temperature of 5% w/w and 10% w/w potato or high-amylose maize starch dispersions with 1 or 2 dual coil heat exchangers. ...................................... 45 

viii

Figure 4-4: Initial view under crossed polarizers of 10% w/w Hylon VII in deionized water that had been processed at 180°C and not dried. .................................................... 47 

Figure 4-5: View under crossed polarizers of 10% w/w Hylon VII in deionized water that had been processed at 180°C and not dried after 24 hours. ............................................. 47 

Figure 4-6: Typical frame of a low spherulite number density sample viewed between crossed polarizers. ............................................................................................................ 51 

Figure 4-7: Typical frame of a moderate spherulite number density sample viewed between crossed polarizers. .............................................................................................. 51 

Figure 4-8: Typical frame of a high spherulite number density sample viewed between crossed polarizers. ............................................................................................................ 52 

Figure 4-9: Diffraction pattern for Trial 6.1 which displays B-type crystallinity .................... 53 

Figure 4-10: Diffraction pattern for Trial 1.1 which displays no crystallinity ......................... 54 

Figure A-1: Feed pump calibration curve ................................................................................ 69 

Figure B-1: Steady state water temperature vs feed pump setting at different oil temperatures. .................................................................................................................... 70 

Figure B-2: Steady state water temperature vs oil temperature at a feed pump setting of 5 Hz. .................................................................................................................................... 71 

Figure C-1: DSC thermograms from Trials 1.1, 1.2, and 2 with repeat measurements. .......... 72 

Figure C-2: DSC thermograms from Trials 3.1, 3.2, 4.1, and 4.2 with repeat measurements. .................................................................................................................. 73 

Figure C-3: DSC thermograms from Trials 5.1, 5.2, 6.1, and 6.2 with repeat measurements. .................................................................................................................. 73 

Figure C-4: DSC thermograms from Trials 7, 8, and 9 with repeat measurements. ................ 74 

Figure C-5: DSC thermograms from Trials 10 and 11 with repeat measurements. ................. 74 

Figure D-1: Solid side view cut away of new hat design ......................................................... 75 

Figure D-2: Side view dimension for new hat manufacture. ................................................... 75 

Figure D-3: Additional side view dimensions for new hat manufacture. ................................ 76 

Figure D-4: Top view dimensions for new hat manufacture. .................................................. 76 

Figure D-5: Front view dimensions for new hat manufacture. ................................................ 77

ix

LIST OF TABLES

Table 3-1: Operating Condition Ranges. ................................................................................. 33 

Table 3-2: Summary of Spray Drying Trials. .......................................................................... 34 

Table 4-1: Total percent recovery for each spray drying trial ................................................. 499 

Table 4-2: Average spherulite size and spherulite number density for each spray drying trial ................................................................................................................................... 50 

Table 4-3: Summary of differential scanning calorimetry results for each trial ...................... 56

Table E-1: Trial 1.1 Supplemental Data .................................................................................. 78 

Table E-2: Trial 1.2 Supplemental Data .................................................................................. 79 

Table E-3: Trial 2 Supplemental Data ..................................................................................... 80 

Table E-4: Trial 3.1 Supplemental Data .................................................................................. 81 

Table E-5: Trial 3.2 Supplemental Data .................................................................................. 82 

Table E-6: Trial 4.1 Supplemental Data .................................................................................. 83 

Table E-7: Trial 4.2 Supplemental Data .................................................................................. 84 

Table E-8: Trial 5.1 Supplemental Data .................................................................................. 85 

Table E-9: Trial 5.2 Supplemental Data .................................................................................. 86 

Table E-10: Trial 6.1 Supplemental Data ................................................................................ 87 

Table E-11: Trial 6.2 Supplemental Data ................................................................................ 88

Table E-12: Trial 7 Supplemental Data ................................................................................... 89 

Table E-13: Trial 8 Supplemental Data ................................................................................... 90 

Table E-14: Trial 9 Supplemental Data ................................................................................... 91 

Table E-15: Trial 10 Supplemental Data ................................................................................. 92 

Table E-16: Trial 11 Supplemental Data ................................................................................. 93 

x

ACKNOWLEDGEMENTS

I would like to thank my research advisor, Dr. Greg Ziegler, for his willingness to

help me throughout this whole process. I think it’s been a learning experience for both of us.

In addition, I’d like to thank Dr. Wayne Curtis for his guidance over the years. I’d also like

to thank Dr. Themis Matsoukas for his always encouraging words when times were tough.

Chris Lane and National Starch also deserve many thanks for their support

My time at Penn State would not have been the same without my great group of

friends. I’m fortunate to have such wonderful people in my life.

My family – my mom, dad, and sister – have made this whole adventure possible.

Their love and support have made me who I am and as I grow older I appreciate all they’ve

done for me more and more. Mom and Dad – thanks for so many day trips to Penn State to

fix broken parts or just to go out to dinner. Kristen – thanks for being the best big sister ever.

I mean that. You really are the best.

And, of course, thanks to Steve for all the late night phone calls and time spent in

lab with me. It would’ve been a miserable couple of years without your love and support.

Chapter 1

Motivation and Objectives

1.1 Introduction

Starch is a botanical biopolymer found in plants in the form of granules. Starch

granules can exist in a variety of shapes, ranging between 10 μm and 100 μm in diameter

(Frazier, Richmond & Donald, 1997). Starch has been used in a variety of applications,

including as an adhesive, to change the appearance of fabric after processing, to prevent the

diffusion of dyes, and for biodegradable packaging (Radley, 1976). Starch is often used,

however, as a food ingredient to enhance flavor or texture or as a filler, gelling agent, or

thickener in foods. In the form of corn, rice, cassava, wheat, and potatoes, starch is the

primary source of calories for much of the world’s population.

Although its name implies a single structure, most starch varieties actually contain a

range of homo-biopolymers, all having the same glucose monomer. These homo-

biopolymers can vary from small, mostly linear molecules, containing 500 to 20,000 glucose

units, to large molecules, containing 1 to 2 million glucose units, with multiple short-chain

branches. The smaller, mainly linear fraction is referred to as amylose, while the large,

heavily branched molecules are referred to as amylopectin. Any homo-biopolymers between

the two extremes, including lightly branched amylose or long chained amylopectin, are

referred to as intermediate material (Eliasson, 2004), although most starch is typically

regarded as having an amylose fraction and an amylopectin fraction, unless otherwise noted.

2

Regardless of the size or degree of branching of the amylose, amylopectin or

intermediate material, all starch is tightly packed into a granule. Within the starch granule,

amylose is present in an amorphous, helical form. The amylose is held within the granule by

semi-crystalline rings of amylopectin (Ring, et al., 1987). Upon heating an aqueous

dispersion of starch to ~50°C to 80°C, depending on the botanical source, the bonds holding

the rigid structure of the starch granule together begin to break, allowing the granule to

expand and amylose to leach out (Frazier, Richmond & Donald, 1997; Radley, 1976).

Heating an aqueous starch dispersion between 50°C to 130°C, depending on the botanical

source, and subsequently cooling it results in the formation of a gel. A gel forms due to the

helical structure of amylose. When amylose is heated in water, portions of the helical

structure will be lost, however some will remain (LeLay & Delmas, 1998). Upon cooling the

dispersion, the helical regions associate and crystallize. These local crystalline regions

prevent further phase separation.

The current hypothesis is that superheating a starch dispersion to at least 160°C results

in complete dissolution of the helical structure of amylose (Creek, Ziegler, & Runt, 2006).

Thus upon cooling, a polymer-rich phase is able to form and crystallize before gelation. The

resulting semi-crystalline structure is called a starch spherulite. Starch spherulites simulate

the mouthfeel of lipid and could be used to encapsulate flavor compounds or probiotics.

They are also a source of soluble dietary fiber and can be dispersed in cold water, unlike

native starch granules (Steeneken & Woortman, 2008). In addition, spherulites melt at

elevated temperatures, typically around 100°C but some as high as 130°C (Creek, Ziegler, &

Runt, 2006), which would allow for food manufacturers to utilize a starch granule-like

ingredient without concern for the changes that result from processing with heat and water,

like the leaching of amylose or the loss of the granular structure.

3

Although starch spherulites have the potential to be a very useful food ingredient, their

physical properties, such as size and crystallinity, must be controlled so that any

commercially produced product has reproducible physical properties. Spray drying has been

shown to be a method of spherulite production (Steeneken & Woortman, 2008), thus this

thesis summarizes the results of using a specific variation of spray drying, termed high

temperature spray drying, to produce semi-crystalline starch spherulites on the pilot plant

scale.

1.2 Motivation

Starch spherulite formation requires heating a starch dispersion to at least 160°C and

cooling at a moderate rate, generally between 10 and 500 °C/min (Nordmark & Ziegler,

2002a; Nordmark & Ziegler, 2002b). This is easily done with lab-scale equipment, such as a

differential scanning calorimeter, but if spherulites are to be of use industrially, they must be

produced on a larger scale. Spray drying offers a way to mass produce spherulites, as it

allows for the rapid cooling and drying of an aerosol spray.

This project was undertaken to investigate the feasibility of producing starch

spherulites via spray drying. Because the starch solution must be heated to at least 160°C, a

variation of spray drying, high temperature spray drying, must be used. High temperature

spray drying is a spray drying process in which an elevated operating line pressure is

maintained to keep the feed solution in the liquid state at operating temperatures that are

above the normal boiling point of the aqueous solution. If the properties of interest cannot be

easily controlled through high temperature spray drying , or spherulite formation is

otherwise impeded, further research would need to be conducted to develop an alternative

unit operation to produce starch spherulites.

4

1.3 Research Objectives

The specific objectives of this research were:

Objective 1. Design a high temperature spray drying system capable of producing starch

spherulites. Since producing starch spherulites requires heating a solution to temperatures of at

least 160°C, the operating pressure must be approximately 10 bar to ensure a liquid state is

maintained prior to atomization. The spray system must be able to accommodate such pressures

and temperatures.

Objective 2. Establish the limiting operating conditions (e.g., feed concentration, feed flow rate,

chamber air temperature, atomization air pressure) for starch spherulite formation via high

temperature spray drying. The limiting operating conditions need to be determined so the

feasibility of the process can be evaluated.

Objective 3. Determine the effect of operating conditions on final product properties (e.g.,

spherulite size, crystallinity, yield).

5

Chapter 2

Literature Review

2.1 Summary of Relevant Literature on Starch

Starch is a botanical polysaccharide, more specifically a homo-biopolymer of α-D-

glucose monomers. The degree of polymerization can range between 500 and 2 million

glucose units (Chaplin, 2009). Two types of glycosidic bonds link the α-D-glucose

monomers, α-1,4 and α-1,6 glycosidic bonds (Figure 2-1) (Frazier, Richmond, & Donald,

1997).

Figure 2-1: α-1,4 and α-1,6 glycosidic bonds connecting α-D-glucose units. Reproduced from Eliasson, 2004.

Starch is stored in the form of granules in vivo. The size and shape of starch granules

varies between botanical sources. Rice granules are typically ~4μm in diameter, while

6

legume granules can be between 10μm and 45μm in diameter (Frazier, Richmond & Donald,

1997). Granules can be found as discs, spheres, ovals, or compound shapes (Jane,

Kasemsuwan, Leas, Zobel, & Robyt, 1994). Regardless of shape or size, starch granules

have alternating semi-crystalline and amorphous layers, due to the radially symmetric

arrangement of the starch polymers within the granule.

Starch that contains mainly α-1,4 glycosidic bonds tends to be small, with only 500 to

20,000 glucose units (Chaplin, 2009). These molecules are called amylose. Amylose

typically accounts for 20% to 30% of the starch in the granule (Parker & Ring, 2001), but

there can be as little as ~3% amylose in waxy maize or greater than 50% amylose in

amylomaizes (Chaplin, 2009). Although amylose molecules contain mainly α-1,4 glycosidic

bonds, there are occasional α-1,6 glycosidic bonds, the number of which depends on the

botanical source of the starch. It’s estimated that less than 4% of the bonds in amylose are of

the α-1,6 variety (Whistler, 1965).

The exact structure of amylose in the granule is still under discussion. It’s generally

accepted, however, that amylose is amorphous (Frazier, Richmond, & Donald, 1997). The α-

1,4 bonds of amylose introduce a turn in the polymer chain, resulting in an overall helical

strcuture (Chaplin, 2009). The amylose helices are not arranged in a crystalline array, which

explains the amorphous nature of amylose. There are six D-glucose monomers per helical

turn resulting in a central cavity (Figure 2-2) (Watanabe, Ogawa, & Ono, 1970). The central

cavity of the helix is somewhat hydrophobic (Frazier, Richmond, & Donald, 1997). This

allows amylose to form inclusion complexes with certain small molecules like free fatty

acids, alcohols and iodine (Heinemann, Escher, & Conde-Petit, 2003; Yamashita, 1965).

7

Figure 2-2: Schematic of helical amylose. Reproduced from The Agrana Group, 2007.

Starch that contains significantly more α-1,6 glycosidic bonds than amylose tends to be

larger, with 1 to 2 million glucose units per molecule (Chaplin, 2009). This type of starch

molecule is referred to as amylopectin. The overall configuration of an amylopectin

molecule is short chains connected at branch points. Amylopectin is fairly sensitive to heat

and acid, both of which preferentially degrade amylopectin at the branch points into short

chains (Byars, 2002; Robin, Mercier, Charonniere, & Guilbot, 1974).

The chains within amylopectin that terminate with no additional branch points, other

than the one from which they stem, are called A-chains. The chain that contains the only

unbound C1, or the sole reducing group of the molecule, is called the C-chain. All other

chains are called B-chains (Parker & Ring, 2001). Figure 2-3 depicts a schematic drawing

of amylopectin. As the majority of chains in amylopectin are A- and B-chains, amylopectin

is thought to have a bimodal chain length distribution with chains of 15-20 glucose residues

(A-chains) and 50-60 glucose residues (B-chains) (Hizukuri, 1985) The ratio of A-chains to

B-chains ranges between 1:1 and 1.5:1, depending on the botanical origin of the starch

(Parker & Ring, 2001).

8

Figure 2-3: Schematic of amylopectin with A, B, and C chains labeled. The open circle represents the lone reducing group. Reproduced from Parker and Ring, 2001.

In the granule, amylopectin is responsible for semi-crystalline rings while amylose is

found primarily in amorphous rings (Frazier, Richmond, & Donald, 1997). Each ring is

between 120 nm and 400 nm thick (Parker & Ring, 2001). A schematic of a typical starch

granule is shown in Figure 2-4a. Some amylose is present at the periphery of the starch

granule and interacts and associates with amylopectin (Jane, 2006) . The tight associations

between amylose and amylopectin at the surface of the starch granule could explain why

uncooked starch is less susceptible to enzymatic digestion than cooked starch (Jane, 2006;

Jane, Ao, Duvick, Yoo, Wong, & Gardner, 2003).

The semi-crystalline regions of the starch granule actually consist of alternating rings

of crystalline and amorphous material, due to the branched structure of amylopectin (Ring,

et al., 1987). As in amylose, the α-1,4 linked chains of amylopectin form helices but, due to

their proximity to one another and their shorter length, these chains tend to form double

helices (Parker & Ring, 2001; Imberty, Buleon, Tran, & Perez, 1988). These double helices

are packed nearly parallel, which allows for strong hydrogen bonding, resulting in regions of

crystallinity. As the α-1,6 branch points do not occur randomly, groupings of α-1,6 branch

points produce amorphous regions (Figure 2-4b) (Ring & Parker, 2001) .

A

B

C

9

Figure 2-4: (a) – Starch granule schematic showing the alternating amorphous (white) and semi-crystalline (gray) layers. Reproduced from Eliasson, 2004. (b) – The semi-crystalline layer consists of alternating amorphous and crystalline layers due to the non-random placement of the branch points of amylopectin and the double helices of the amylopectin A-chains. Reproduced from Jane, 2006.

The idea that amylopectin is responsible for the semi-crystalline regions of starch has

been confirmed through a variety of studies. The most convincing evidence is that the

internal structure of waxy maize starch, which contains very little amylose, is very similar to

the internal structure of normal maize starch (Chen, Yu, Chen, & Li, 2006). Chen, Yu, Chen,

and Li (2006) also found that the crystallinity of the starch granule correlated with the

amount of amylopectin in the granule. This is expected if amylopectin, not amylose, is

responsible for crystallinity. Others have shown that upon subjecting starch granules to acid

hydrolysis, the acid preferentially attacked the amorphous regions (Robin, Mercier,

Charbonniere, & Guilbot, 1974). The remaining crystalline regions consisted of short chains

linked together via branching, similar to the structure of amylopectin. Collectively, these

studies imply that amylopectin, rather than amylose, is responsible for the crystallinity of

starch granules.

(a) (b)

10

In its application as food or a food ingredient, starch typically must be heated in excess

water prior to use. Native starch granules are resistant to digestion and insoluble in cold

water. When placed in cold water, the granules may absorb a small amount of water and

swell slightly (Parker, 2003). This swelling is reversible up to approximately 60°C or 70°C,

depending on the source of the starch (Parker, 2003). Upon further heating, an aqueous

starch suspension undergoes gelatinization. The term gelatinization encompasses all

irreversible structural changes that occur when an aqueous starch dispersion is heated and

the crystalline regions of the granule are disrupted. Not only does gelatinization allow for

starch to be digested, but it is also responsible for starch’s ability to be used as a filler or

thickener in foods.

The exact temperature at which gelatinization occurs varies for each starch source, but

it is typically between 50°C and 100°C, although it can be as high as 150°C for high-

amylose starches (Frazier, Richmond, & Donald, 1997). Upon reaching the gelatinization

temperature, the granules irreversibly swell (Radley, 1976). This occurs as water diffuses

into the granule and disrupts the hydrogen bonds in the crystalline region. Since the

hydrogen bonds can no longer keep the amylopectin tightly packed, the granule is able to

expand. The granular expansion and disruption of the crystalline amylopectin network

allows for the movement of the smaller, more mobile amylose molecules out of the granule.

The amount of leached amylose increases as the temperature increases (Radley, 1968).

The dispersed leached amylose has a unique form. Portions of amylose retain a helical

structure, while other portions assume a random coil (Figure 2-5) (Jordan, Brant, & Cesaro,

1978; LeLay & Delmas, 1998). It is hypothesized that the helical portions of the amylose act

as nematic liquid crystals, which is defined by random distribution throughout the solution

but all pointing in a single direction (Creek, Ziegler, & Runt, 2006). Building on this

hypothesis, it is suggested that when a gelatinized starch solution is cooled, the helical

11

portions of the amylose crystallize into double helices, thereby locking the random coil

section of amylose in place. In addition, the swollen granules that still contain amylopectin,

but little amylose, act as filler molecules giving additional stability and crystallization to the

gel. The more common name for the phenomenon of forming a locally crystalline network

from the leached amylose is gelation.

Figure 2-5: Perspective drawing of a representative 100-residue amylose chain with portions of random, amorphous coil and portions of helices. The helical portions were highlighted by the author. Circles represent glycosidic oxygen and lines are virtual bonds. Reproduced from Jordan, Brant, and Cesaro, 1978.

2.2 Summary of Relevant Literature on Spherulites

Under certain processing conditions, short, linear polymers, like amylose, often

crystallize in a spherulitic morphology. Spherulites are radially symmetric, birefringent, and

thereby exhibit a “Maltese cross” when viewed between crossed polarizers of a light

microscope (Figure 2-6). More broadly, however, a spherulite is defined as a spherical

structure with symmetric spatial ordering that extends from a central point in three

12

dimensions (Creek, 2007). This implies that spherulites do not necessarily have to contain

any crystalline material; however, experimentally produced starch spherulites are semi-

crystalline, containing both crystalline and amorphous regions (Nordmark & Ziegler,

2002b). Although starch granules are also semi-crystalline, starch spherulites crystallized

from amylose are not incipient starch granules formed in vitro. There have been no

convincing reports of granule formation from gelatinized starch or polysaccharide mixtures

(Nordmark & Ziegler, 2002a; Gidley & Cooke, 1991). It has been proposed, however, that

granule formation involves a mechanism similar to spherulitic crystallization since starch

spherulites from high-amylose maize starch exhibit similar physical properties as young

starch granules. (Nordmark & Ziegler, 2002a; Ziegler, Creek, and Runt, 2005).

Figure 2-6: Starch spherulites under polarized light presented by Creek, 2007. Scale bar is 50 μm.

Starch spherulites offer unique functionality, particularly as a food ingredient. Starch

spherulites form a spreadable, gel-like paste when suspended. This paste exhibits more

effective gelling properties than maltodextrin, which is currently used as a starch-based fat

substitute (Steeneken & Woortman, 2008). In addition, starch spherulites could be used to

13

encapsulate flavors. Starch spherulites are partially resistant to enzymatic digestion, due in

part to the arrangement of the crystalline unit cell. Starch spherulites typically have what is

called a B-type arrangement (Nordmark & Ziegler, 2002a). Starches with a B-type unit cell

are more resistant to enzymatic digestion than starches with other unit cell configurations

(Annison & Topping, 1994). For starch spherulites, this means that they can act as a soluble

fiber to deliver probiotics to the colon. Clearly, a low-calorie fat substitute that could be

flavored and used to promote gastrointestinal health is worth pursuing on a large scale

production.

A number of factors influence both the ability of a starch dispersion to crystallize into a

spherulitic morphology and the physical properties of any produced spherulites, such as size

and percent crystallinity. The initial concentration of the starch dispersion, the maximum

heating temperature, the cooling rate, and the quench temperature can all encourage or

impede spherulitic crystallization. In addition, three kinetically controlled phenomena must

occur in the proper order to produce a died powder of starch spherulites. The processing

conditions and system must allow for phase separation of the gelatinized starch dispersion

into a polymer-rich phase and a solvent-rich phase to occur first. The polymer-rich phase

must then crystallize before being dried. If the order of phase separation, crystallization, and

drying is changed, the starch dispersion will not form dried spherulites.

When using high-amylose starches, the polymer-rich phase is mainly amylose. When

using normal starches, the polymer-rich phase contains both amylose and amylopectin.

These two polymers are immiscible, though, so within the polymer-rich phase is an amylose-

rich phase and an amylopectin-rich phase (Hermansoon, Kidman, & Svegmark, 1995). In the

research for this thesis, a high-amylose maize starch was used. Unless otherwise noted, the

process for spherulite formation will assume an aqueous dispersion of high-amylose maize

14

and any phase separation will result in an amylose-rich (polymer-rich) phase, and a water-

rich (solvent-rich) phase.

Starch spherulites have been produced by crystallizing native starches, but it appears

that only the amylose crystallizes (Nordmark & Ziegler, 2002a; Nordmark & Ziegler,

2002b). The amount of branched or especially large material in solution has a direct impact

on the ability of the solution to form spherulites. As more of this type of material is added,

the produced spherulites decrease in size and finally will not form (Chowdhury, Haigh,

Mandelkern, & Alamo, 1998). Early research suggested that a lipid was required for starch

spherulite formation (Davies, Miller, & Proctor, 1980; Fanta, Felker, & Shogren, 2002),

however that has been questioned in recent years (Creek, 2007; Nordmark & Ziegler,

2002b).

The hypothesis that starch spherulites form from the crystallization of amylose has

been supported by a number of studies. Research has shown that starch spherulites are

abundant and easily formed when using purified amylose or a starch with a high amylose

content (Nordmark & Ziegler, 2002a). Ziegler, Nordmark, and Woodling (2003) showed a

grainy, non-spherulitic material which visually increased as the amount of amylopectin

increased. Ziegler, Nordmark, and Woodling (2003) also showed that acid-modified maize

starch produced numerous spherulites. Previous research concluded that acid-modification

preferentially hydrolyses amylopectin at its branch points to produce a material that is

enriched in short, linear chains (Wang & Wang, 2001). The idea that acid-modified starch,

which is rich in short, linear polymers, produces more numerous spherulites than non-

modified starch, supports the hypothesis that starch spherulite formation results from the

crystallization of amylose, as amylose is also a short, linear polymer. It is worth noting that

amylopectin from purified waxy maize starch can produce a few spherulites, however, the

spherulites produced are likely to have been the result of amylose contamination in the

15

sample or thermal degradation of the amylopectin into short, linear chains, since no other

convincing reports of starch spherulite formation from amylopectin exist (Nordmark &

Ziegler, 2002a). Because amylose appears to be the fraction of starch that crystallizes in a

spherulitic morphology, using a high-amylose starch would likely aid in producing starch

spherulites.

The maximum heating temperature and phase separation of the dispersion are closely

related. A starch dispersion must be heated to at least 160°C, but preferably 180°C, for

significant spherulite formation. It is hypothesized that between 160°C and 180°C, the

amylose liquid crystals transition into random coils, and the dispersion becomes isotropic.

Similar phase transitions have been studied in non-glucose polymers. Guenet (1996) found

that polystyrene gels had stiff chains whose inability to fold was a key factor for gelation.

For starch spherulite formation, such gelation must be avoided. If amylose completely loses

the portions of stiff, helical structure at higher temperatures, it would partially explain why a

higher temperature produces an increased number of well-defined spherulites rather than a

gel. If the solution is not heated sufficiently for amylose to experience the helix coil

transition, starch spherulites will not form due to the presence of single helices locally

crystallizing upon cooling and preventing phase separation into a polymer-rich phase with a

concentration appropriate for spherulite formation.

Increasing the maximum heating temperature results in more well-defined spherulites.

For example, acid-modified starch produced numerous but poorly defined spherulites when

heated to lower temperatures, around 160°C; however, heating the acid-modified starch to

180°C resulted in well-developed spherulites (Ziegler, Nordmark, & Woodling, 2003). The

exact temperature required for significant well-defined spherulite formation varies slightly

between each starch source, however, it does not seems to be as vastly influenced by

botanical origin as gelatinization temperature. Ziegler, Nordmark, and Woodling (2003)

16

showed that both mung bean and potato starch require temperatures of 180°C for significant

spherulite formation, where as the gelatinization temperatures vary about 10°C between the

two starches (Califano & Anon, 2006; Shiotsubo, 1984). The method of heating does not

appear to impact the formation of spherulites, as both indirect and direct heating have been

used to produce spherulites (Nordmark & Ziegler, 2002a; Nordmark & Ziegler,

2002b;Steeneken & Wootman, 2008; Ziegler, Nordmark, & Woodling, 2003).

A number of hypotheses exist to explain why an elevated temperature is necessary for

spherulite production. In addition to inducing the helix coil transition and removing

nuclei for non-spherulitic crystallization (Ziegler, Nordmark, & Woodling, 2003; Creek,

Ziegler, & Runt, 2006), superheating an aqueous starch dispersion could result in the

degradation of the amylopectin into short, linear, intermediate material with fewer branch

points per molecule than unmodified amylopectin and therefore more spherulite formation

material in solution (Nordmark & Ziegler, 2002b; Vesterinen, Suortti, Autio, 2001).

Nordmark and Ziegler (2002a) and Creek (2007) have separately investigated the effect

of cooling rate on spherulite production. Nordmark and Ziegler (2002a) found that moderate

cooling rates had a small effect on the diameter of spherulites, but extreme cooling rates

could impede the formation of spherulites. Extremely rapid cooling, by immersing a sample

in liquid nitrogen, and extremely slow cooling, 1°C/min, did not produce spherulites from

gelatinized ae 70 high amylose starch (Nordmark & Ziegler, 2002a). This starch did,

however, produce well defined spherulites at moderate cooling rates, 10°C/min to

500°C/min. Creek (2007) found that a 10% w/w mung bean starch in water solution that was

cooled slowly, 2.5°C/min and 1°C/min, had an increased the amount of “salt and pepper”

non-spherulitic material.

Both extremely fast and extremely slow cooling rates impede spherulite formation, but

the method of inhibition varies. Extremely fast cooling rates do not allow time for phase

17

separation of the dispersion into a polymer-rich phase and a polymer-poor phase prior to

crystallization. Extremely slow cooling rates also resulted in poor spherulite formation

because it allowed for localized crystallization prior to the demixing (Ziegler, Creek, &

Runt, 2005). When crystallization occurs before demixing, a gel-like structure could develop

that prevents further phase separation from occurring.

Overall, the cooling rate can impact that ability of a solution to form spherulites as well

as alter the properties of the spherulites. Slow cooling rates produce slightly larger

spherulites than rapid cooling rates. Rapid cooling rates, however, produce more well-

defined spherulites. Extreme rates, either very fast or very slow, disrupt the balance between

phase separation and crystallization to the extent that spherulites will not form.

The quench temperature can also impact spherulite formation. This is the temperature

to which the heated starch dispersion is cooled. Creek, Ziegler, and Runt (2006) found that

dispersions of 10% dry mass amylose from common maize starch in water would produce

well-defined spherulites only at quench temperatures of 60°C and below. Quench

temperatures above 70 °C resulted in no spherulites. Between 60°C and 70 °C is a transition

region in which spherulites will form, however they are often poorly defined . As the phase

separation into polymer-rich and solvent-rich phases occurs during cooling, the degree of

cooling can have an impact on the ability of the dispersion to phase separate. It’s possible

that a quench temperature above 70°C reduces the degree of phase separation to the point

where there the concentration of the polymer-rich phase is too low for spherulitic

crystallization.

Most reports agree that well-defined spherulites can be formed from a 10% w/w

dispersion of normal or high-amylose starch or purified amylose in water (Nordmark &

Ziegler, 2002a; Nordmark & Zielger, 2002b; Ring, et al., 1987; Ziegler, Nordmark, &

Woodling, 2003). Ring et al. (1987) produced spherulites from a 5% w/w solution of short-

18

chain amylose (degree of polymerization 22), however this result was not reproduced by

Ziegler, Nordmark, and Woodling (2003) using potato starch or acid-modified maize starch.

Although it is interesting that there appears to be a lower limit to the feed concentration, it is

not particularly useful information for this research as increasing the feed concentration

would be more economical. Creek (2007) reported an upper concentration limit for amylose

dispersions heated to 180°C. The degree of polymerization of the amylose impacted the

upper limit, which ranged between 35% w/w to 60% w/w. Most researchers impose 30%

w/w as the upper limit so it can be imposed on a number of starch species (Nordmark &

Ziegler, 2002a; Nordmark & Ziegler, 2002b; Ring et al., 1987; Ziegler, Nordmark, &

Woodling, 2003). Steeneken and Woortman (2008) did, however, find that spherulites would

form from a 40% w/w potato starch dispersion if the dispersion was heated to 200°C. Creek

(2007) investigated the impact of starch concentration on the size of the produced spherulites

and found that a 10% w/w mung bean starch in water solution produced spherulites that

were essentially the same size as spherulites from a 20% w/w mung bean starch in water

dispersion.

Since spray drying is the proposed method of spherulite production, it would be

advantageous to produce spherulites at an elevated feed concentration because any

additional water in the feed would simply be evaporated and dried in the spray drying

process and unable to be recovered for additional use. It is likely, though, that there is an

upper operational limit to the starch concentration which may or may not coincide with the

upper limit for spherulite formation. If the operational concentration is too high, more than

one spherulite could crystallize per droplet, due to the increased amount of material, which

could result in spherulite aggregation or clumping. In addition, because water evaporates

during the drying process, the concentration in the droplets may increase above the upper

limit for spherulite formation if the initial operation concentration is too high. The optimal

19

feed concentration would be one that reduces the amount of water that would be wasted

while still producing non-aggregated spherulites.

2.3 Summary of Relevant Literature on Spray Drying

Spray drying is a process that transforms a liquid feed into a dry form by atomizing the

feed into a hot drying medium (Masters, 1985). Spray drying was proposed as a method for

starch spherulite production because of its widespread use in making powders. In addition,

spray drying is an economical, quick, controllable, and reasonably well understood process

which can be easily implemented in industry.

Current applications for spray drying allow for control over the size, degree of

crystallinity, and degree of drying or remaining moisture, among other properties. Most

spray dryers are set up with three distinct regions – the atomizing region, the drying

chamber, and the product collection region. Typically, the user has control over a number of

operational variables that impact the properties of the final product. These variables include

inlet air moisture, inlet air temperature, feed flow rate, drying air flow rate, feed

concentration, and atomization air pressure,. The overall basic spray drying process can be

broken down into four phases – atomization of liquid feed, spray/air contact, moisture

removal, and product recovery (Masters, 1985).

The atomization of the feed is defined as the formation of a spray by breaking up the

bulk feed liquid and any dissolved or suspended solids into individual droplets to be dried

(American Institute of Chemical Engineers, 2003). In general, atomization is a two step

process. First, the liquid feed is broken into large droplets or filaments immediately after

leaving the nozzle. Then, as the drops travel further from the nozzle, the larger droplets

break into smaller droplets due largely to surface tension and flow properties. There are two

20

main methods of producing droplets – via rotary atomizers or via nozzles. Nozzles can be

further broken into two categories - one-fluid nozzles or via two-fluid nozzles. In a one-fluid

nozzle, the liquid feed moves through the nozzle and exits in a conical sheet. The sheet that

leaves the nozzle then breaks into droplets. As the pressure in the nozzle increases due to an

increased feed flow rate or a decreased nozzle orifice, the sheet length decreases and

droplets form faster. Two-fluid nozzles break up the feed stream with high velocity gas. The

flow of the high velocity gas results in frictional forces over the surface of the liquid feed

causing the feed to disintegrate into droplets.

By controlling the atomization process, the particle size distribution of the dried

product can be regulated. The diameter of the nozzle orifice and the pressure of the fluid and

atomizing air, if applicable, have a direct impact on the properties of the final product. For a

given liquid feed pressure, as the diameter of the orifice increases, the feed rate also

increases resulting in increased droplet size as more fluid must be present to maintain the

pressure (Masters, 1985). If the feed rate is held constant as the orifice diameter increases,

the fluid experiences less pressure and force as it exits the nozzle, allowing for larger

droplets to form (Masters, 1985). For two-fluid nozzles, the atomizing air pressure also

affects the droplet size (American Institute of Chemical Engineers, 2003). Increasing the

atomizing air pressure at a constant feed rate creates smaller droplets, resulting in high

density fine particles (Chidavaenzi, Graham, Koosha, & Pathak, 1997). The initial

concentration of the feed can also impact the product size. Increasing concentration

increases feed viscosity which in turn produces course sprays, which in turn increases

particle size and bulk density (Chidavaenzi, Graham, Koosha, & Pathak, 1997). An increase

in feed temperature lowers viscosity thereby decreasing droplet size (Chidavaenzi, Graham,

Koosha, & Pathak, 1997). Although other configurations are possible, the feed is often

21

atomized at the top of the drying chamber; this configuration will be assumed for the

remainder of the thesis, unless otherwise stated.

The spray-air contact and moisture removal phases of spray drying are closely related

and often discussed together. The drying medium, assumed to be hot air, typically enters the

drying chamber either from the top, in co-current drying, or the bottom, in counter-current

drying. If the air enters the drying chamber from the bottom, the hottest air is in contact with

the driest particles which presents the potential for thermal degradation or scorching.

Counter-current drying does, however, provide excellent efficiency in heat utilization. Co-

current drying is less efficient but widely used, especially when drying heat labile products.

During co-current drying, the spray droplets are subjected to the highest temperature when

they possess the most water so most of the heat is used to evaporate water. This results in the

temperature of the product remaining relatively low and constant. Both counter- and co-

current drying can effectively dry products in short time periods, depending on the

properties of the feed and air. The choice of one setup over the other generally depends on

the properties of the product to be dried.

When a sprayed droplet is placed in contact with hot air, water begins to evaporate

from the surface (Minoshima, Matsushima, Liang, & Shinohara, 2001). Generally, the initial

solids concentration is uniform within the sprayed droplet and the rate of evaporation is

fairly fast (Charlesworth & Marshall, 1960). The drying rate is, however, somewhat related

to the solids concentration in the droplet. The higher the concentration, the slower the drying

rate, although even a ‘slow’ drying rate is still very rapid (Hecht & King, 2000). Initially,

when the drying rate is relatively quick, a higher concentration at the droplet surface is

produced as the droplet is dried, since particles suspended in the droplet do not have time to

disperse as water is removed from the surface (Minoshima, Matsushima, Liang, &

Shinohara, 2001). Although the surface concentration increases, drying will occur at a

22

constant rate so long as water is able to diffuse fast enough through the droplet to maintain

saturated conditions at the surface (Masters, 1985). The majority of drying occurs during this

first constant rate phase of the drying process.

It’s been shown that by varying the drying air temperature, the crystallinity of the final

product can be altered (Chiou, Langrish, & Braham, 2008). The hotter the drying air, the

more crystalline the final product (Wallack, El-Sayed, & King, 1990). The drying air

temperature and the amount of air used also impacts the final moisture content of the product

(Shabde & Hoo, 2006). The hotter the air, or the more that is supplied, the drier the final

product, which is expected.

The final step in spray drying is separating the dried product from the drying medium.

Industrially this is an important step since economically recovering the product is of upmost

importance. Economic recovery includes recovering as much of the initial feed as possible in

the form that is most salable, such as within a given size distribution range. Although care

can be taken to minimize the particle size distribution of the product through the design of

the spray dryer and the selection of operating conditions, there will always be some very fine

particles present. Collecting these potentially air-borne particles is extremely important

industrially as to meet any environmental goals and protect workers’ safety. The product

recovery step occurs via two separations. The primary separation involves recovering

sellable product, while the secondary separation involved removing the fine, dust-like

particles from the exhaust air (Masters, 1985).

In most spray drying processes, the liquid feed is water based and is sprayed into hot

air, but different setups can and do occur depending on the manufacturer’s needs. There are

a number of variations to the basic spray drying process such as spray cooling, spray freeze

drying, low temperature spray drying, and spray reaction (Masters, 1985). Spray cooling air

is only warm enough to allow for the solidification of the droplets. Spray freeze drying

23

atomizes the feed into freezing air, which freezes the water in the droplet. Water removal

then occurs through sublimation under vacuum. Low temperature spray drying utilizes low

temperature air as the drying medium as to prevent thermal degradation of the product or

product scorching. In spray reaction systems, the liquid feed is atomized and put in contact

with a reactant drying gas. The large surface area of the atomized feed droplets results in a

fast reaction rate.

High temperature spray drying occurs when the temperature of the feed solution is

above normal boiling point of the feed. This presents some interesting design criteria.

Because the feed must be pumped and atomized, it must be in the liquid state upon reaching

the nozzle. In order for a solution to be in the liquid state, the pressure of the solution must

be greater than the saturation pressure at the operating temperature. Thus, high temperature

spray drying operates at elevated temperatures and pressures and extreme care must be taken

to ensure the safety of the operator.

High temperature spray drying is also unique in the method of drying. Not only are

conventional methods used, such as hot or cold air, but flash evaporation is also a key drying

element for high temperature spray drying. Since the drying chamber is generally at

atmospheric pressure, when the pressurized feed is atomized, some of the water in the

droplets will immediately flash off. The remaining water will evaporate as expected. Water

will be removed from the surface of the droplet, keeping the crystallizing spherulite at a near

constant temperature. As described before, drying will occur at a constant rate as long as

saturated conditions exist on the surface of the droplet.

If spray drying is to be used to produce starch spherulites, high temperature spray

drying must be employed as the feed must be raised to 180°C. It is reasonable to think that

high temperature spray drying can be used to make starch spherulites as Steeneken and

Woortman (2008) found that starch spherulites can be produced by spray drying a starch

24

dispersion after it had been superheated. They found that if a starch solution was first gelled

then homogenized and fed into a spray dryer, the spherulites produced were more well-

defined than spherulites produced without the intermediate gelling step. The recovered yield

was also greater when an intermediate gelling step was in place (Steeneken & Woortman,

2008).

The mechanism of starch spherulite production via high temperature spray drying is

similar to the process for starch spherulites prepared on the lab-scale through the use of

differential scanning calorimeters. Superheating the feed dispersion will result in the helix

coil transition, as hypothesized by Creek, Ziegler, and Runt (2006). The cooling that

occurs between heating and drying, including the temperature decrease upon atomization

due to flash evaporation, will encourage the phase separation of the feed into polymer-rich

and solvent-rich phases. If atomization and the size of the droplets is controlled, one

polymer-rich phase will exist per droplet which can then rapidly crystallize before fully

drying. If drying occurs before the phase separation is complete, non-spherulitic spray dried

starch, rather than starch spherulites, will form.

2.4 Summary

Starch is comprised of homo-biopolymers with an α-D-glucose monomer. Generally,

these homo-biopolymers can be categorized as amylose or amylopectin. Although both

amylose and amylopectin have the same monomer, their physical structures are significantly

different. Amylose is roughly linear, while amylopectin is much larger and is branched. Both

amylose and amylopectin are stored in starch granules in vivo. Upon heating in excess water,

granules undergo a transition called gelatinization. This irreversible change allows the starch

granules to crystallize upon cooling.

25

If gelatinized starch is superheated and cooled at a moderate rate, the amylose from the

starch will crystallize in a spherulitic morphology. Starch spherulites are radially symmetric,

semi-crystalline, and have the potential to be a useful food ingredient. Certain processing

requirements must be met in order for a starch dispersion to crystallize into well-defined

spherulites. The dispersion must be superheated to roughly 180°C and cooled below 70°C at

a rate between 10°C/min and 500°C/min. During cooling, the dispersion phase separates into

a polymer-rich phase and a solvent-rich phase. The polymer-rich phase then rapidly

crystallizes in a spherulitic morphology.

It has been suggested that spherulites can be produced by using high temperature spray

drying. High temperature spray drying is a spray drying variation in which the feed solution

is processed at an operating temperature above the normal boiling point of the solution,

which in this case is water. This requires that the pressure in the line is also elevated to keep

the feed in the liquid state. When using high temperature spray drying, some of the solvent

will flash off upon atomization due to the atmospheric pressure of the drying tower. This is

advantageous for spherulite formation, as it rapidly reduces the temperature of the atomized

droplets, which is necessary for spherulite formation.

26

Chapter 3

Materials and Methodolgy

3.1 Materials

A modified Tall Form Spray Dryer/Chiller FT 80/81 from Armfield (Hampshire,

England) was used for all spray drying purposes (Figure 3-1 and Figure 3-2). A Mica Band

Heater from Watlow (St. Louis, MO, Code # STB8A2A20) and a PID controller from

Shimaden (Tokyo, Japan, Model # SR22-1Y-000) were used to monitor and control the

temperature of the starch dispersion in the spray dryer feed vessel (Figure 3-3). Mobile 1

5W-30 Fully Synthetic Motor Oil was used in a NESLAB EX-7 Heater/Circulator from

Thermo-Fisher (Waltham, MA, Cat. # 1-813-316) to heat the dispersion in two consecutive

Parker Dual Heat Transfer Coils (Cleveland, OH, Cat. # 4295) (Figure 3-4 and Figure 3-5).

A CRES Ultra Response inline heater from Infinity Fluids (Norwich, CT, Model # CRES-

ILA24-6) was used as a supplemental heater. High-amylose maize starch (Hylon VII,

National Starch, Bridgewater, NJ, Ref #E748-35) was used as the starch species. Deionized

water was used in the preparation of the dispersions.

27

Figure 3-1: The drying tower of the Armfield Tall Form Spray Dryer/Chiller FT 80/81 used for this thesis.

28

Figure 3-2: The modified Armfield Tall Form Spray Dryer/Chiller FT 80/81 used for this thesis.

29

Figure 3-3: The feed vessel, feed pump, band heater and controller used with the spray dryer for this thesis.

30

Figure 3-4: The insulated consecutive dual coil heat exchanger system.

Feed Inlet (1st heat exchanger)

Feed Connection (1st to 2nd

heat exchanger)

Feed Outlet (2nd heat exchanger)

Oil Inlet (2nd heat exchanger)

Oil Connection (2nd to 1st

heat exchanger)

Oil Outlet (1st heat exchanger)

1st heat exchanger

2nd heat exchanger

31

Figure 3-5: The first of two dual coil heat exchangers used, uncovered.

3.2 Sample Preparation

Aqueous dispersions of high-amylose maize starch (10, 20, and 30 % w/w) were

prepared prior to processing. The concentration of the prepared dispersion was dictated by

the experimental design. The solutions were heated on a hot plate to ~90°C and stirred with

a magnetic stir bar prior to use.

32

3.3 Experimental Design

The range of the specific operating conditions of interest were established through a

combination of preliminary experiments and guidelines suggested by the spray dryer user

manual (K. Kaylegian, personal communication, October 18, 2007). The operating

conditions deemed controllable included: feed concentration, feed flow rate, feed

temperature, atomization nozzle diameter, atomization air pressure, and drying air

temperature. Atomization air pressure was neglected for further study as the spherulites

produced at a low atomization air pressure (0.5 bar, as suggested by spray dryer operation

guidelines(K. Kaylegian, personal communication, October 18, 2007)) were small to begin

with (approximately 7μm) and increasing the atomization air pressure would only further

decrease the diameter of the spherulites, making capture difficult. The atomization nozzle

diameter was neglected as a preliminary experiment showed that increasing the nozzle

diameter from 0.012” to 0.028” caused an increase in the particle size distribution. In an

effort to produce spherulites of a uniform size, it was advantageous to use the smallest

nozzle diameter, 0.012”, and a constant, low atomization air pressure. The feed pump setting

range of 5 Hz to 10 Hz, which had a direct and proportional impact on the feed flow rate,

was established through the observation that increasing the pump setting above 10 Hz

increased the line pressure well above 15 bar, which was deemed unsafe. The lower limit

was established based on spray dryer operation guidelines (K. Kaylegian, personal

communication, October 18, 2007). The operating range for the feed concentration and

solution temperature were both established based on the standard protocol of previously

published work (Nordmark & Ziegler, 2002a; Nordmark & Ziegler, 2002b). The drying

temperature range was established based on spray dryer operation guidelines (K. Kaylegian,

33

personal communication, October 18, 2007). Table 3-1 summarizes the range of operating

conditions which were investigated.

Table 3-1: Operating Condition Ranges.

Variable Lower Limit Upper Limit

Feed Concentration 10 % w/w 30 % w/w Feed Pump Setting (Feed Flow Rate)

5 Hz (0.287 mL/s)

10 Hz (0.612 mL/s)

Feed Temperature 160 °C 180 °C

Drying Air Temperature 150 °C 250 °C

In order to determine the effect of the operating conditions on the properties of the

final spray dried product, a fractional factorial experimental design was developed using

ECHIP software (ECHIP, Inc., Hockessin, DE). A fractional factorial experimental design is

useful when a preliminary information about a system is required. Table 3-2 summarizes the

operating conditions for each experimental trial. Trials 1, 3, 4, 5, and 6 were repeated.

34

Table 3-2: Summary of Spray Drying Trials.

Trial Number

Feed Concentration

Operating Inline Temperature

Feed Pump Setting

Feed Flow Rate

Drying Air Temperature

(% w/w) (°C) (Hz) (mL/s) (°C)

1.1 10 180 10 0.612 250

2 30 160 5 0.287 150

3.1 30 160 10 0.612 250

4.1 10 180 5 0.287 150

5.1 30 180 5 0.287 250

6.1 10 160 10 0.612 150

7 30 180 10 0.612 150

8 10 170 5 0.287 250

9 30 180 10 0.612 250

10 10 170 5 0.287 150

11 20 170 7.5 0.4495 200

1.2 10 180 10 0.612 250

3.2 30 160 10 0.612 250

4.2 10 180 5 0.287 150

5.2 30 180 5 0.287 250

6.2 10 160 10 0.612 150

3.4 Experimental Methodology

3.4.1 Spray System Description

The overall process flow diagram can be seen in Figure 3-6. The heated feed was held

at approximately 90°C in the feed vessel. As mentioned, the temperature of the solution in

the feed vessel was monitored and controlled by a band heater and PID controller (P-value

20, I-value 120, D-value 0). The feed pump moved the product from the feed vessel though

two consecutive dual tube heat exchangers. A NESLAB EX-7 Heater/Circulator from

Thermo-Fisher was used to heat and pump heat transfer oil through the 3/8-inch shell of both

35

heat exchangers. Mobile 1 5W-30 Fully Synthetic Motor Oil was used at the heat transfer oil

and was heated to a temperature of 189.5°C. The temperature of the oil was controlled by

the internal PID controller (P-value 0.6, I-value 0.6, D-value 0) of the heater/circulator. The

product flowed countercurrent to the oil through the inner ¼-inch tube of the heat

exchangers. The product then left the dual coil heat exchangers and flowed through an

Infinity CRES Ultra Response inline heater. The inline heater was packed with stainless

steel mesh packing as a static mixer to encourage mixing and even heating and the

temperature was controlled by an external Cole-Parmer temperature controller (Vernon

Hills, IL, Model # 89810-02). After leaving the inline heater, the feed was pumped to the

two-fluid atomization nozzle where it was sprayed into the drying tower.

Figure 3-6: Process flow diagram of high temperature spray drying system.

36

3.4.2 Spraying Methodology

To determine the feasibility of producing spherulites via high temperature spray drying, a

500 mL aqueous dispersion of high-amylose maize starch (10% w/w) was prepared and

heated and stirred on a hot plate. Deionized water was initially pumped through the system

at a feed pump setting of 5 Hz, corresponding to a flow rate of 0.287 mL/s, while the oil

heater/circulator began heating the oil to the 189.5°C setpoint. Air was supplied to the

actuator in the nozzle, allowing the water to exit the system. When the heater/circulator

reached steady state, indicated by a constant oil temperature equal to the set point, the inline

heater was turned on and allowed to reach the set point.

The system was run until there was minimal water in the feed vessel, at which point the

starch dispersion was removed from the hot plate, poured into the feed vessel, and held at

approximately 90°C. In order to prevent the starch from settling out of solution, the solution

in the feed vessel was stirred by hand. The oil in the NESLAB EX7 circulated through the

shell of the heat exchangers at a constant rate of 15 L/min while the starch dispersion was

pumped at a feed pump setting of 5 Hz (0.287 mL/s). The feed was not dried in the spray

dryer at the time. A sample was collected as the feed exited the nozzle.

To determine the effect of the operating conditions on the properties of the final product,

aqueous solutions (200 mL) of the prescribed concentration were prepared and heated and

stirred. The inlet and exhaust fans of the spray dryer were set and energized such that the

cyclone differential pressure remained between -0.1 mbar and -0.8 mbar, as recommended

by the manufacturer (K. Kaylegian, personal communication, October 18, 2007). The drying

air heater was also activated and run to reduce the relative humidity in the drying chambers.

Upon reaching a relative humidity of approximately 2%, air at 2 bar was supplied to

the actuator and air at 0.5 bar was supplied to the atomizer. Deionized water was pumped

37

through the system at the prescribed flow rate while the oil was heated to the setpoint of

189.5°C. The oil flowed through the dual coil heat exchangers at a constant flow rate of 15

L/min. When the oil reached the set point, the inline heater was turned on and set to the

prescribed feed temperature. Upon the inline heater reaching the setpoint and a low water

level in the feed vessel, the prepared starch dispersion was added to the feed vessel and

stirred by hand. When the solution level in the feed vessel was low (approximately 20 mL

remaining), 500 mL of deionized water was added to the feed vessel to flush the system.

After the system was flushed, the feed pump, drying air heater, inlet and exhaust fans, inline

heater, heater/circulator, atomization air, and actuator air were all shut down in order to

safely collect the dried product.

3.5 Data Analysis Methodology

3.5.1 Light Microscopy

Light microscopy was used to determine the presence of spherulites, the size of the

produced spherulites, and the spherulite number density. Samples from the initial spherulite

formation experiment were used as they were collected in a liquid form. For samples from

the spray drying trials, approximately 0.05 g of dried starch was dispersed in 1 mL of

deionized water. To establish the presence of spherulites in a given sample, one drop of the

starch dispersion was placed on a glass slide and viewed between the crossed polarizers of a

Olympus BX41 light microscope from Hitech Instruments (Edgemont, PA). SPOT

Advanced software from Diagnostic Insturments, Inc. (Sterling Hills, MI) was used for all

microscopy analysis.

38

Spherulite size was determined by calculating the average diameter from a sample

of 50, or as many as could be found, spherulites from random locations on the slide. The

diameters of the spherulites sampled were manually measured by constructing a horizontal

line across the spherulites in brightfield (40x magnification) to more accurately determine

the boundaries. Spherulite number density was determined based on the ease of locating

spherulites to sample for sizing. If less than 50 well-defined spherulites were present, the

sample was classified as having a low spherulite number density. If there was an average of

less than 5 spherulites per field but at least 50 well-defined spherulites were present, the

sample was classified as having a moderate spherulite number density. If the average

number of spherulites per field was greater than or equal to 5 and 50 well-defined spherulites

were present, the sample was classified as having a high spherulite number density.

Image analysis was not attempted as it would have provided inaccurate results.

There were particles visible in brightfield which did not exhibit the Maltese cross of

spherulites when viewed with polarized light. Thus, imagine analysis would have

overestimated the number of spherulites. If image analysis was attempted in polarized light,

the diameter of the spherulites would not have been as accurate because the edges of the

Maltese crosses, indicating spherulites, were not distinct enough to use for image analysis.

3.5.2 Percent Recovery

The percent recovery was defined as the percent of initial starch that was easily

recovered (i.e., did not have to be scrapped off the walls of the spray dryer). Very little of

the dried starch was on the walls of the spray dryer. The mass of starch recovered from the

cyclone collection vessel, the cyclone butterfly valve, the cyclone, and the main drying

chamber and drying chamber collection vessel were individually weighed on an Ohaus

39

Galaxy 200 balance (Pine Brook, NJ). Samples that were not fully dried were centrifuged

and washed, once each with deionized water, ethanol (Pharmco-Aaper, cat.# 111000200),

and acetone (Sigma-Aldrich, cat.# 179124). After the final centrifugation, the samples were

placed in a dessicator for three days to dry before being massed.

3.5.3 X-Ray Diffraction

X-ray diffraction (XRD) was used to measure the percent crystallinity of a sample.

In XRD, an x-ray beam is directed at the sample, which scatters the beam. The scattered

radiation is collected on a detector. The produced diffraction pattern shows sharp peaks for

crystalline material and broad curves for amorphous material.

The samples analyzed with XRD were from the same collection location as the

samples viewed with the microscope. In addition, XRD provided information regarding the

arrangement of the crystalline unit cell. Samples used for XRD analysis were stored in an

85% relative humidity environment over potassium chloride (KCl) for 2 days to allow the

moisture in the samples to equilibrate. The XRD analysis was conducted using a Rigaku

MiniFlexII Desktop X-ray Diffractometer (The Woodlands, TX) and software from Rigaku

(The Woodlands, TX). A small amount of sample was pressed into a flat pellet with an

Econo-Press from SpectraTech, Inc. (Shelton, CT) and scanned continuously from 4° to 30°

2Θ at a rate of 1.0 °/min and data were collected at intervals of 0.02°.

3.5.4 Differential Scanning Calorimetry

Differential scanning calorimetry (DSC) was used as a qualitative analysis method

to confirm the results obtained from the other analytical methods. In DSC, the amount of

40

heat required to establish a negligible temperature difference between a sample and a

reference is measured as the two are subjected to a temperature change. DSC was chosen as

an analytic method because the thermograms of starch spherulites are well documented

(Nordmark & Ziegler, 2002a; Nordmark & Ziegler, 2002b; Creek, 2007).

Samples were prepared in duplicate for each trial. The samples for DSC were taken

from the same collection location as the samples for microscopy and XRD. Approximately 5

mg of starch was weighed into a high-volume (60 μL) stainless-steel DSC pan (Perkin-

Elmer Instruments, Norwalk, CT). 45 μL of deionized water was added before the pan was

sealed with a gasketed lid and stored for approximately 24 hours to allow for moisture

equilibration. The pan was heated using a differential scanning calorimeter (either Perkin-

Elmer DSC 7, Norwalk, CT or TA Instruments DSC Q 100, New Castle, DE) from 10°C

to 180°C at10°C/min then cooled to 20°C at 20°C/min. An empty DSC pan was used as

a reference for all analyses. The collected data was analyzed using Pyris software

(Perkin-Elmer) or Universal Analysis 200 software (TA Instruments, New Castle, DE).

41

Chapter 4

Results and Discussion

4.1 Spray System Design

4.1.1 Process Modifications

Although much of the spray dryer was unmodified, new tubing, a new nozzle, and a new

hat were all required. Flexible metal tubing (Swagelok, SS-FL4-VF4VF4) was installed in

place of the provided plastic tubing. A new nozzle was specially manufactured by Spraying

Systems (Wheaton, IL) and required the development of a new hat (Figure 4-1). The hat

was designed with assistance from Randall Bock of Penn State University and manufactured

from 304 stainless steel by Brooks Welding (State College, PA).

42

Figure 4-1: The new hat, lower, developed to accommodate the new atomizer. The hat supplied with the spray dyer is in also shown for comparison, upper.

The nozzle from Spraying Systems was designed to withstand the high fluid pressure

and would only open if air was applied to an actuator (Figure 4-2). Upon applying 2 bar of

air to the actuator, the nozzle would open allowing the product stream to exit. If no air was

applied, the nozzle would be closed and no liquid would be allowed to exit. Because of this,

the user could manually increase the line pressure by cutting air to the actuator as a closed

nozzle would result in a buildup of fluid and thus an increase in pressure in the line.

43

Figure 4-2: New atomizing nozzle by Spraying Systems, Inc (Wheaton, IL).

When dealing with hot fluids under pressure, care was taken to ensure that the system

was operated as safely as possible. The heat exchangers and pipes containing hot oil were

wrapped with fiberglass insulation, a pressure release valve with a cracking pressure of

around 20 bar and a manual override system was installed in the product line, and a check

valve with a cracking pressure of approximately 10 bar was installed in the product line

immediately prior to the atomization nozzle.

4.1.2 Design Justification

The band heater used to heat the feed vessel was used to increase the efficiency of

the dual coil heat exchangers by lower the amount of energy needed to raise the feed to the

operating temperature. The use of the band heater has the added advantage of preventing

gelation when pregelatinized starch is used. By keeping the feed vessel at an elevated

temperature, approximately 90°C, a pregelatinized dispersion will not cool enough to form a

Actuator air line

Feed line Atomizing air line

44

gel and potentially clog the system. High amylose maize starch, however gelatinizes at a

temperature of 150°C, so this added benefit of the band heater does not apply.

The heat transfer oil was selected because it is economical and safe to use up to

200°C. Two consecutive dual coil heat exchangers in addition to an inline heater were used

as a result of the natural progression of the system development. From the data collected

during preliminary trials, it was concluded that one dual coil heat exchanger was not

sufficient to reach the necessary temperatures for spherulite formation. Upon the addition of

a second dual coil heat exchanger, the operating temperatures of various starch dispersions

(either 5% or 10%, w/w) were still not sufficiently high (Figure 4-3). The inline heater was

added to increase the feed temperature to the desired operating temperature. The inline

heater was not chosen as the sole heater because the amount of heat necessary to increase the

temperature of the feed from 90°C to 180°C (315 J/g) would have to be supplied in a short

amount of time, due to the dimensions of the heater. This would cause the starch to burn on

to the heating element, as the heating element was in direct contact with the starch

dispersion, and reduce its efficiency. By using two dual coil heat exchangers prior to the

inline heater, the temperature difference between the inlet and outlet of the inline heater was

small enough to prevent burn-on. The stainless steel packing was used so as to increase

mixing within the inline heater to ensure that all of the fluid reached the proper temperature

and to prevent scorching.

45

Figure 4-3: Operating temperature of 5% w/w and 10% w/w potato or high-amylose maize starch dispersions with 1 or 2 dual coil heat exchangers.

Flexible metal tubing was installed throughout the system due to the elevated

temperature and pressure requirements for spherulite formation. The flexible metal tubing

ensures that the system could withstand a temperature of at least 180°C and a pressure of at

least 10 bar. Throughout the system, the flexible metal tubing was wrapped with fiberglass

insulation to minimize heat loss. The pressure relief valve was installed to ensure that if a

blockage in the line occurred there would not be an excessive buildup of pressure. The

breaking pressure of the valve was set to around 20 bar. The check valve prior to the nozzle

was necessary to make sure the proper pressure was obtained.

4.2 Spherulite Formation

When the sample of starch that was not spray dried was viewed, only a few

spherulites were initially present (Figure 4-4). However, as the objective was simply to

46

produce spherulites this was deemed acceptable. Upon allowing the sample to sit at room

temperature for 24 hours, a separation occurred and the number of spherulites increased

notably (Figure 4-5). This phenomena can be explained by considering the mechanism of

starch spherulite production. In order to produce starch spherulites, a superheated starch

dispersion must experience a phase separation followed by crystallization during cooling. By

allowing the liquid sample to quiescently sit for 24 hours, the solution had time to phase

separate which increased the amylose concentration in the polymer-rich phase which

allowed spherulites to crystallize. Prior to the phase separation, the polymer concentration

was low, which meant the rate of crystallization was low. The rate of crystallization could be

increased, and thus the time needed for spherulite formation decreased, by increasing the

concentration in dispersion, either by allowing for a phase separation or by removing some

of the solvent. When using high temperature spray drying, some of the water flash

evaporates when the heated feed leaves that atomizing nozzle. This immediately increases

the amylose concentration in the droplet. Phase separation within the droplet would further

increase the amylose concentration, thereby decreasing the time needed for spherulitic

crystallization.

47

Figure 4-4: Initial view under crossed polarizers of 10% w/w Hylon VII in deionized water that had been processed at 180°C and not dried.

Figure 4-5: View under crossed polarizers of 10% w/w Hylon VII in deionized water that had been processed at 180°C and not dried after 24 hours.

48

4.3 Analysis of Spray Drying Trials

The collected data was statistically analyzed using ECHIP software (ECHIP, Inc.,

Hockessin, DE). This software utilized a simple linear regression to determine if there was a

correlation between the controlled operating parameter (feed concentration, feed flow rate,

maximum heating temperature, and drying air temperature) and the measured spherulite

properties (formation, size, number density, and crystallinity).

There was a relationship between the initial feed concentration and the percent

recovery, the feed flow rate and the percent recovery, and the drying air temperature and the

percent recovery; however, there was a lack of fit for the data. No other controlled

operational conditions exhibited an influence on the measured outputs. Because of the data

having either lack of fit for the linear regression or no correlation, the results are discussed

below from a qualitative standpoint in order to still gain knowledge for future research.

4.3.1 Percent Recovery Results

Table 4-1 shows the percent recovery information for the specific trials. Between

81% and 99% of the recovered starch came from cyclone collection vessel and butterfly.

This is expected as particularly small particles would be captured by the fine particle

collection system. Particles large enough to be collected in the drying tower collection vessel

were not produced. Most of the samples were recovered as dry powders, except for Trial 6.1

where the cyclone collection vessel contained a liquid starch dispersion which had to be

dried prior to analysis.

49

Table 4-1: Total percent recovery for each spray drying trial

Trial Number

Total Percent Recovery

1.1 13

1.2 8

2 17

3.1 18

3.2 13

4.1 19

4.2 12

5.1 5

5.2 14

6.1 2

6.2 5

7 5

8 44

9 22

10 21

11 16

One might expect the replicated trials to produce similar results. For the percent

recovery, however, replicated trials did not produce similar results. A possible explanation

for the irregularities is that some other operating condition, which was not controlled,

impacts percent recovery more than the four selected variables (concentration, flow rate,

operating temperature and drying air).

The low percent recovery values imply that most of the starch was bypassing

collection and trapped in the fine particle collection system. This could not be confirmed as

the fine particle collection system contained a variety of spray dried products and could not

be regularly cleaned. In order for high temperature spray drying to be an economical method

of starch spherulite production, the average percent recovery would have to be significantly

50

improved. Increased recovery could be achieved by increasing the size of the spherulites, so

that more were captured in the cyclone collection vessel or by having a more efficient fines

collection system. It is also worth noting that a pilot scale test such as this could have

substantially lower yields as compared to full scale operation if only due to materials surface

to process volume ratio.

4.3.2 Spherulite Size and Number Density

Table 4-2 displays the average particle size and number density. Figure 4-6, Figure

4-7, and Figure 4-8 show typical field of low (value 1), moderate (value 2), and high (value

3) spherulite number density samples, respectively.

Table 4-2: Average spherulite size and spherulite number density for each spray drying trial

Trial Number

Average Size (μm)

Spherulite Number Density

1.1 6.7 3 1.2 7.9 1 2 5.6 1

3.1 7.7 1 3.2 7.0 2 4.1 5.8 3 4.2 7.8 1 5.1 5.1 2 5.2 7.7 1 6.1 6.0 2 6.2 5.5 1 7 6.1 1 8 5.7 2 9 7.1 1

10 6.7 1 11 6.8 1

51

Figure 4-6: Typical frame of a low spherulite number density sample viewed between crossed polarizers.

Figure 4-7: Typical frame of a moderate spherulite number density sample viewed between crossed polarizers.

52

Figure 4-8: Typical frame of a high spherulite number density sample viewed between crossed polarizers.

Although the majority of the spherulites produced ranged between ±2 μm of the

average particle size, some trials produced spherulites that were ±6μm of the average.

Although maintaining a uniform size is of concern for industrial production, the operating

conditions that most affected the size distribution could not be determined, due to the small

number of spherulites sampled.

The small spherulite diameter could partially explain the low percent recovery.

According to the spray dryer operation manual, the system typically produces particles that

are 20μm to 120μm in diameter (K. Kaylegian, personal communication, October 18, 2007).

As the spherulites were much smaller in diameter, the spray dryer may not be equipped to

collect such small particles.

53

4.3.3 Percent Crystallinity

Only one trial exhibited a crystalline pattern when a sample was analyzed by x-ray

diffraction (XRD). Trail 6.1 produced a diffraction pattern that was similar to the B-type

diffraction pattern of other spherulitic samples (Creek, 2007; Nordmark & Zielger, 2002a).

The percent crystallinity of the sample from Trial 6.1 was determined to be 21%. This was

done by constructing an amorphous halo with the method used by Evans (2005) (Figure 4-

9). The region between the baseline and the amorphous halo results from the amorphous

content of a sample. The region between the amorphous halo and the diffraction pattern

results from the crystalline content of a sample.

The sample from Trial 6.1 was the only sample to be collected as a wet dispersion,

rather than a dried powder. As the sample was not washed and dried right away, the solution

had significantly longer time to phase separate and crystallize. This could explain why it was

the only sample to produce a diffraction pattern that implied a semi-crystalline sample.

Figure 4-9: Diffraction pattern for Trial 6.1 which displays B-type crystallinity

baseline

54

The remainder of the samples produced diffraction patterns similar to Figure 4-10.

This implies that the remainder of the samples were amorphous within the limits of detection

by XRD. In contrast, both microscopy and differential scanning calorimetry (presented

below) suggest that the produced starch spherulites are semi-crystalline. Microscopy showed

that all samples contained some spherulites, which are visible between crossed polarizers

because of their semi-crystalline structure. As such, XRD should have reported some degree

of crystallinity. It is possible that the percentage of crystalline material in the sample was too

small to detect, as microscopy showed a significant amount of non-spherulitic material. If

the non-spherulitic material was amorphous and the spherulites themselves were partially

amorphous, the percent crystallinity of the sample would be incredibly low and masked by

the more prevalent amorphous material.

Figure 4-10: Diffraction pattern for Trial 1.1 which displays no crystallinity

55

4.3.4 Differential Scanning Calorimetry

A summary of the results of the differential scanning calorimetry (DSC) analysis

can be found in Table 4-3. Many of the thermograms contained overlapping peaks, due to

any amylopectin, retrograded amylose, or starch/lipid inclusion complexes that may have

been in the sample. Because of these impurities, it was difficult to establish the peak limits.

In addition, the peak limits had to be manually selected so a degree of subjectivity exists in

the results. Typically, spherulitic samples will have a peak temperature around 90°C to

100°C and a ΔHfus of approximately 10 J/g (Creek, Ziegler, & Runt, 2006; Nordmark &

Ziegler, 2002a). Thus, peaks around 90°C to 100°C were examined closely.

56

Table 4-3: Summary of differential scanning calorimetry results for each trial

Trial Repeat

Measurement

Low Limit

High Limit

Peak ΔHfus

(°C) (°C) (°C) (J/g)

1.1 #1 51.56 103.71 77.5 26.783

#2 32.24 96.47 77.37 37.799

1.2 #1 83.19 103.58 83.87 1.442

#2 78.12 106.13 86.37 4.142

2.1 #1 65.05 114.86 88.37 23.752

#2 60.45 113.26 97.03 14.534

3.1 #1 66.69 128.61 95.45 12.75

#2 70.81 120.72 95.7 7.52

3.2 #1 66.78 114.04 94.53 8.518

#2 53.98 109.45 73.2 5.677

4.1 #1 83.07 117.96 95.2 20.222

#2 68.58 109.02 92.83 19.342

4.2 #1 83.57 107.88 90.2 5.07

#2 63.62 110.67 89.03 11.627

5.1 #1 85.44 107.78 90.2 12.144

#2 41.17 97.89 81.53 16.213

5.2 #1 62.96 113.99 88.24 16.61

#2 63.43 122.95 95.27 10.27

6.1 #1 51.43 104.99 81.2 10.301

#2 54.26 105.53 81.2 9.619

6.2 #1 85.23 119.24 92.87 7.515

#2 66.62 104.02 90.7 3.559

7 #1 74.52 114.01 78.53 4.354

#2 85.83 127.85 93.72 6.352

8 #1 67.94 122.37 102.45 7.878

#2 81.33 120.38 97.74 5.57

9 #1 77.54 106.96 89.4 3.06

#2 81.73 110.71 95.24 3.088

10 #1 73.11 103.58 94.66 7.469

#2 69.01 124.68 94.88 13.22

11 #1 74.58 134.27 93.17 10.49

#2 66.34 116.42 94.53 9.089

57

The variations in peak limits, peak temperature, and ΔHfus values highlight the

variability in the samples. It is possible that different components of the samples settled in

different areas of the sample container. This would explain why repeat measurements

yielded results that were sometimes 200% greater than the first measurement. In spite of

efforts to mix the samples prior to preparing the DSC pans, different elements of the sample

could have concentrated in different areas, resulting in DSC pans being filled with a non-

representative powder. Based on the percent recovery, spherulite size, and spherulite number

density results, it is not surprising that replicated trials yielded different results.

Although DSC could be used to determine the percent crystallinity of the samples,

the variability of the DSC data would have yielded results that were so varied they were not

useable. Thus, the data from DSC was used to confirm the presence of spherulites, as

evidenced by peak temperatures in the 90°C to 100°C range, that were of low crystallinity,

as evidenced by the low ΔHfus values. Both of these observations were generally supported

by the other analysis methods. The large ΔHfus values for samples that did not exhibit a

crystalline diffraction pattern could be explained by another component melting. Starch/lipid

inclusion complexes also melt around 100°C and have been known to form from the lipid

found in native starch. In addition, the thermograms were rather complex and did not

possess the smooth, broad endotherm reported by Creek, Ziegler, and Runt (2006) and

Nordmark and Ziegler (2002a). Complexities could have resulted from another component

melting, such as a starch/lipid inclusion complex, or from an impurity in the sample.

4.4 Supplemental Analysis

In an effort to determine the root cause of the variation in the samples, operating

conditions that were recorded but not controlled were analyzed with the ECHIP software.

58

These conditions included the relative humidity at when the starch solution was first

introduced to the system, the relative humidity when water used to flush the system was first

introduced, the maximum and minimum chamber pressure values, and the cyclone

differential pressure. As with the controlled operating conditions, the software either

reported no relationship, or a relationship with a lack of fit for the data. This implies that

something that was not be observed or controlled with the current setup and methodology,

such as the atomization process, may have impacted the results of interest.

Chapter 5

Conclusion and Future Work

5.1 Conclusion

Starch spherulites offer unique functionality as a food ingredient. They are a source

of soluble dietary fiber that are dispersible in cold water, have the mouthfeel of a lipid, and

can be used to encapsulate flavor compounds or nutriceuticals. In addition, they can be

produced by high temperature spray drying, which theoretically makes their production on

the industrial scale possible. This thesis presented information about the production of starch

spherulites via high temperature spray drying that laid the foundation for continued research.

As spherulites were present in all samples collected, the first research objective, to

design and build a high temperature spray drying system capable of producing starch

spherulites, was met. The second objective, to establish the limiting operating conditions,

was partially met. Spherulites formed from all operating conditions. However, it is

advantageous to have a range in which spherulites are known to be produced with high

temperature spray drying as it provides a foundation upon which to base future research. In

addition, the limiting operating conditions, such as the maximum feed flow rate, may not

apply under different setups. While they are limiting for the current setup, further research

would need to be done under a variety of setups to determine if they are universally limiting

conditions, like maximum heating temperature appears to be. The third objective, to

determine the effect of the operating conditions on the final product properties, was

attempted but not achieved. A relationship that could be mathematically modeled, and thus

60

optimized, could not be determined due to the high degree of variability in the samples and

the small amount of preliminary data.

Although more variability existed than initially expected, the research performed for

this thesis yielded relevant and valuable information. First and foremost, this research

confirmed that high temperature spray drying is a method that can be used to produce starch

spherulites. Because of the high degree of variability in the samples, controlling the process

was not possible for a project of this scope. Further research would be need to be done to

determine if the variability is inherent to the high temperature spray drying process or if it

was a result of the current setup.

Secondly, this research provided significant evidence that the rate of drying was too

rapid for the conditions explored in this pilot plant scale unit. This was demonstrated by both

the spherulite formation experiment and spray drying Trail 6.1 in which the sample was

collected as a liquid and allowed to quiescently rest before analysis. Allowing the sample

time to rest before analysis resulted in more time for crystallization. Thus, the sample

yielded results that were expected, based on prior knowledge of spherulites. The replicated

DSC results from Trial 6.1 were much closer than any other sample and more consistent

with the DSC data from other spherulitic samples. Trial 6.1 was also the only sample to

produce a diffraction pattern from XRD. Had all samples been as consistent in producing

data that agreed with prior knowledge, it is likely that the impact of the operating conditions

could have been determined. As it was, this research laid the foundation for future work on

the controlled and optimized production of starch spherulites.

61

5.2 Future Work

With the results presented in this thesis in mind, a number of experiments could be

performed to increase the base of knowledge regarding starch spherulite production via high

temperature spray drying. The primary concern of future work should be to increase the

spherulitic yield and percent recovery of the spherulites. Without a larger yield, it would be

not be feasible to produce starch spherulites industrially due to product loss. If the yield is

increased, the size distribution could be analyzed and controlled, as there would be more

spherulites per sample. There are a number of ways to increase the yield, some of which are

outlined below.

One of the main results from this thesis was that more spherulites crystallized over

time from samples that were collected a liquid and allowed to quiescently rest after heating.

This implies that drying the heated feed immediately is detrimental to the formation of

starch spherulites because there isn’t enough time for the amylose to crystallize before

drying. Thus, increasing the residence time of the sample in the drying tower should be

investigated. In addition, if the residence time of the system was increased, the drying air

temperature could be decreased since the degree of drying is related to the time spent in the

drying tower and the temperature of the drying air. Decreasing the drying air temperature

would allow more time for the amylose to crystallize before drying. It is possible to alter to

residence time by more closely monitoring and adjusting the cyclone differential pressure

and the inlet and exhaust fan settings.

It would also be worth investigating the possibility of cooling the solution en masse

prior to atomization. By cooling the bulk solution prior to atomization, there is an increased

opportunity for phase separation which leads to an increased amount of material, and

therefore faster crystallization rate. Cooling the solution en masse could be accomplished a

62

number of ways: by separating the high temperature spray drying process into two steps, by

cooling the feed inline, by using a counter-current spray drying system, or by using a

combination spray chiller/dryer.

If the process is separated into two steps, the feed could be run through the spray

system, but not atomized or dried. The feed could be collected, allowed to quiescently rest

for a given time period to allow for phase separation and crystallization, then run through the

spray system again, being atomized and dried but not heated. If the system was cooled

inline, another heat exchanger would be required to remove heat from the system after

heating the feed. If this option were pursued, the maximum heating temperature, the time

held at that temperature, and the degree of cooling would all have to be investigated. By

cooling the solution prior to drying and allowing for additional phase separation and

crystallization, the degree of crystallization could be studied and controlled.

A version of a counter current spray drying system would increase the amount of

time necessary for a particle to dry as the driest air would be in contact with the driest

particles, and the most humid air would be in contact with the wettest particles. In addition,

as most industrial counter-current spay systems introduce the feed from the bottom and the

drying air from the top, the sprayed droplets and particles would have to be sprayed upwards

and then fall back down, increasing the amount of time in the drying tower. Again, the

longer the particles are in the drying tower, the lower the necessary drying air temperature,

which would allow for additional time for phase separation and crystallization. A fourth

option to increase phase separation and crystallization before drying would be to use a

combination spray chiller/dryer, in which the atomized spray is chilled such that it remains a

liquid. The collected slurry would then be moved to a second atomizer where it could be

dried. The time allowed for crystallization would depend on the slurry volume collected. If a

63

large volume was collected, the time before drying would also be large which would result

in additional crystallization.

Although high-amylose maize contains an elevated amount of amylose as compared

to common corn or potato starch, its elevated gelatinization temperature may impact the

formation of starch spherulites in ways unseen. It would be worth investigating the effect of

different starch species on the ease of producing starch spherulites via high temperature

spray drying.

Finally, the overall goal should not be forgotten. Each subsequent experiment should

be undertaken with the intent of advancing the knowledge of starch spherulite production via

high temperature spray drying until it is a well-understood and controlled process.

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69

Appendix A

Feed Pump Calibration Curve

As no data was supplied relating the feed pump setting to the feed flow rate, the

following graph was developed.

Figure A-1: Feed pump calibration curve

70

Appendix B

Effect of Feed Flow Rate and Oil Temperature on Operating Temperature for Water

When only one heat exchanger was used, the following curve was developed to

relate the temperature of the oil to the temperature of the feed at various flow rates. In this

case, water was used as the feed, for economical reasons.

Figure B-1: Steady state water temperature vs feed pump setting at different oil temperatures.

At a feed pump setting of 5 Hz, the temperature of the water was discontinuous, as

seen below. This discontinuity contributed to the addition of the Infinity inline heater, as

without it, there would have been no way to reach a temperature of 170°C, had the

experimental design called for it.

71

Figure B-2: Steady state water temperature vs oil temperature at a feed pump setting of 5 Hz.

72

Appendix C

Differential Scanning Calorimetry Results

The following graphs show the DSC curves from the different spray drying

trials.

Figure C-1: DSC thermograms from Trials 1.1, 1.2, and 2 with repeat measurements.

73

Figure C-2: DSC thermograms from Trials 3.1, 3.2, 4.1, and 4.2 with repeat measurements.

Figure C-3: DSC thermograms from Trials 5.1, 5.2, 6.1, and 6.2 with repeat measurements.

74

Figure C-4: DSC thermograms from Trials 7, 8, and 9 with repeat measurements.

Figure C-5: DSC thermograms from Trials 10 and 11 with repeat measurements.

75

Appendix D

Hat Design Sketches

The following figures show the design sketches for the new hat that was

manufactured specifically for this research project. The shape was determined based on the

original hat dimensions and the shape of the new nozzle.

Figure D-1: Solid side view cut away of new hat design

Figure D-2: Side view dimension for new hat manufacture.

76

Figure D-3: Additional side view dimensions for new hat manufacture.

Figure D-4: Top view dimensions for new hat manufacture.

77

Figure D-5: Front view dimensions for new hat manufacture.

78

Appendix E

Supplemental Data for Spray Drying Trials

Table E-1: Trial 1.1 Supplemental Data

Trial #  1.1     Date  3/8/009          

% Starch  10  % w/w    

Volume  250  mL    

Theoretical Starch  27.7777  g    

Actual Starch  27.7703  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  10  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  24.5  Hz 

Oil T Operating (°C)  181.5  (°C)  Exhaust Fan  37.25  Hz 

   Chamber Pressure ‐0.24 to  ‐0.47  mbar 

In‐line T (°F)  356  (°F)    

In‐line P (psi)  200  (psi)    

   Cyclone Differential Pressure  3.3  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

30  % start    

70  % end    

     

                          

79

Table E-2: Trial 1.2 Supplemental Data

Trial #  1.2     Date  3/13/2009          

% Starch  10  % w/w    

Volume  200  mL    

Theoretical Starch  22.2222  g    

Actual Starch  22.1402  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  10  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  23  Hz 

Oil T Operating (°C)  185.6  (°C)  Exhaust Fan  37.25  Hz 

   Chamber Pressure ‐0.22 to ‐0.39  mbar 

In‐line T (°F)  356  (°F)    

In‐line P (psi)  160  (psi)    

   Cyclone Differential Pressure  3  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

21.3  % start    

34  % end    

     

                          

80

Table E-3: Trial 2 Supplemental Data

Trial #  2     Date  3/9/2009          

% Starch  30  % w/w    

Volume  200  mL    

Theoretical Starch  85.7143  g    

Actual Starch  85.6528  g    

Feed T  160  (°C)  320  (°F)    

Flow Rate  5  Hz    

Drying  T  150  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  25  Hz 

Oil T Operating (°C)  189.5  (°C)  Exhaust Fan  36.7  Hz 

   Chamber Pressure ‐0.35 to ‐0.57  mbar 

In‐line T (°F)  230  (°F)    

In‐line P (psi)  170  (psi)    

   Cyclone Differential Pressure  3.2  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

38.7  % start    

30.2  % end    

     

                          

81

Table E-4: Trial 3.1 Supplemental Data

Trial #  3.1     Date  3/11/2009          

% Starch  30  % w/w    

Volume  200  mL    

Theoretical Starch  85.7143  g    

Actual Starch  85.7165  g    

Feed T  160  (°C)  320  (°F)    

Flow Rate  10  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  24.4  Hz 

Oil T Operating (°C)  179.6  (°C)  Exhaust Fan  38  Hz 

   Chamber Pressure ‐0.31 to ‐0.59  mbar 

In‐line T (°F)  230  (°F)    

In‐line P (psi)  155  (psi)    

   Cyclone Differential Pressure  3.1  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

22  % start    

35  % end    

     

                          

82

Table E-5: Trial 3.2 Supplemental Data

Trial #  3.2     Date  3/14/2009          

% Starch  30  % w/w    

Volume  200  mL    

Theoretical Starch  85.7143  g    

Actual Starch  85.7102  g    

Feed T  160  (°C)  320  (°F)    

Flow Rate  10  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  23  Hz 

Oil T Operating (°C)  179  (°C)  Exhaust Fan  37.4  Hz 

   Chamber Pressure ‐0.3 to  ‐0.58  mbar 

In‐line T (°F)  230  (°F)    

In‐line P (psi)  150  (psi)    

   Cyclone Differential Pressure  2.9  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

30.6  % start    

38.6  % end    

     

                          

83

Table E-6: Trial 4.1 Supplemental Data

Trial #  4.1     Date  3/8/2009          

% Starch  10  % w/w    

Volume  250  mL    

Theoretical Starch  27.7777  g    

Actual Starch  27.7705  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  5  Hz    

Drying  T  150  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  25.5  Hz 

Oil T Operating (°C)  188  (°C)  Exhaust Fan  37  Hz 

   Chamber Pressure ‐0.07 to  ‐0.43  mbar 

In‐line T (°F)  356  (°F)    

In‐line P (psi)  170  (psi)    

   Cyclone Differential Pressure  3.4  mbar 

   Feed Pressure  7.9  bar 

Relative Humidity 

37  % start    

32  % end    

     

                          

84

Table E-7: Trial 4.2 Supplemental Data

Trial #  4.2     Date  3/13/2009          

% Starch  10  % w/w    

Volume  200  mL    

Theoretical Starch  22.2222  g    

Actual Starch  22.1643  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  5  Hz    

Drying  T  150  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  23.75  Hz 

Oil T Operating (°C)  183.1  (°C)  Exhaust Fan  35  Hz 

   Chamber Pressure ‐0.26 to  ‐0.6  mbar 

In‐line T (°F)  356  (°F)    

In‐line P (psi)  150  (psi)    

   Cyclone Differential Pressure  2.8  mbar 

   Feed Pressure  7.9  bar 

Relative Humidity 

34.7  % start    

31  % end    

     

                          

85

Table E-8: Trial 5.1 Supplemental Data

Trial #  5.1     Date  3/9/2009          

% Starch  30  % w/w    

Volume  200  mL    

Theoretical Starch  85.7143  g    

Actual Starch  85.7012  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  5  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  25  Hz 

Oil T Operating (°C)  189.5  (°C)  Exhaust Fan  37.5  Hz 

   Chamber Pressure ‐0.1 to  ‐0.32  mbar 

In‐line T (°F)  356  (°F)    

In‐line P (psi)  165  (psi)    

   Cyclone Differential Pressure  3.1  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

2.1  % start    

3.5  % end    

     

                          

86

Table E-9: Trial 5.2 Supplemental Data

Trial #  5.2     Date  3/12/2009          

% Starch  30  % w/w    

Volume  200  mL    

Theoretical Starch  85.7143  g    

Actual Starch  85.6824  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  5  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  24.1  Hz 

Oil T Operating (°C)  188.2  (°C)  Exhaust Fan  38  Hz 

   Chamber Pressure ‐0.24 to  ‐0.43  mbar 

In‐line T (°F)  356  (°F)    

In‐line P (psi)  165  (psi)    

   Cyclone Differential Pressure  3  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

17  % start    

7.7  % end    

     

                          

87

Table E-10: Trial 6.1 Supplemental Data

Trial #  6.1     Date  3/10/2009          

% Starch  10  % w/w    

Volume  200  mL    

Theoretical Starch  22.2222  g    

Actual Starch  22.2968  g    

Feed T  160  (°C)  320  (°F)    

Flow Rate  10  Hz    

Drying  T  150  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  26  Hz 

Oil T Operating (°C)  186.6  (°C)  Exhaust Fan  37.9  Hz 

   Chamber Pressure ‐0.26 to  ‐0.72  mbar 

In‐line T (°F)  230  (°F)    

In‐line P (psi)  170  (psi)    

   Cyclone Differential Pressure  3.3  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

38.1  % start    

17  % end    

     

                          

88

Table E-11: Trial 6.2 Supplemental Data

Trial #  6.2     Date  3/14/2009          

% Starch  10  % w/w    

Volume  200  mL    

Theoretical Starch  22.2222  g    

Actual Starch  22.1716  g    

Feed T  160  (°C)  320  (°F)    

Flow Rate  10  Hz    

Drying  T  150  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  23  Hz 

Oil T Operating (°C)  182.1  (°C)  Exhaust Fan  34.4  Hz 

   Chamber Pressure ‐0.14 to  ‐0.5  mbar 

In‐line T (°F)  230  (°F)    

In‐line P (psi)  155  (psi)    

   Cyclone Differential Pressure  2.6  mbar 

   Feed Pressure  7.9  bar 

Relative Humidity 

4.7  % start    

50.2  % end    

     

                          

89

Table E-12: Trial 7 Supplemental Data

Trial #  7     Date  3/11/2009          

% Starch  30  % w/w    

Volume  200  mL    

Theoretical Starch  85.7.143  g    

Actual Starch  85.6837  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  10  Hz    

Drying  T  150  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  24.7  Hz 

Oil T Operating (°C)  188  (°C)  Exhaust Fan  36.5  Hz 

   Chamber Pressure ‐0.26 to ‐0.56  mbar 

In‐line T (°F)  356  (°F)    

In‐line P (psi)  155  (psi)    

   Cyclone Differential Pressure  2.8  mbar 

   Feed Pressure  7.9  bar 

Relative Humidity 

57.5  % start    

70.3  % end    

     

                          

90

Table E-13: Trial 8 Supplemental Data

Trial #  8     Date  3/6/2009          

% Starch  10  % w/w    

Volume  300  mL    

Theoretical Starch  33.3333  g    

Actual Starch  33.3321  g    

Feed T  170  (°C)  338  (°F)    

Flow Rate  5  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  25  Hz 

Oil T Operating (°C)  189.5  (°C)  Exhaust Fan  38  Hz 

   Chamber Pressure ‐0.16 to ‐0.39  mbar 

In‐line T (°F)  338  (°F)    

In‐line P (psi)  150  (psi)    

   Cyclone Differential Pressure  3.3  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

14  % start    

11  % end    

     

                          

91

Table E-14: Trial 9 Supplemental Data

Trial #  9     Date  3/12/2009          

% Starch  30  % w/w    

Volume  200  mL    

Theoretical Starch  85.7143  g    

Actual Starch  85.6791  g    

Feed T  180  (°C)  356  (°F)    

Flow Rate  10  Hz    

Drying  T  250  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  24.35  Hz 

Oil T Operating (°C)  178.5  (°C)  Exhaust Fan  37.8  Hz 

   Chamber Pressure ‐0.12 to ‐0.39  mbar

In‐line T (°F)  356  (°F)    

In‐line P (psi)  160  (psi)    

   Cyclone Differential Pressure  3.3  mbar

   Feed Pressure  7.91  bar 

Relative Humidity 

24.4  % start    

28.5  % end    

     

                          

92

Table E-15: Trial 10 Supplemental Data

Trial #  10     Date  3/5/2009          

% Starch  10  % w/w    

Volume  400  mL    

Theoretical Starch  44.4444  g    

Actual Starch  44.4508  g    

Feed T  170  (°C)  338  (°F)    

Flow Rate  5  Hz    

Drying  T  150  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  25.6  Hz 

Oil T Operating (°C)  189.1  (°C)  Exhaust Fan  37.25  Hz 

   Chamber Pressure ‐0.31 to ‐0.7  mbar 

In‐line T (°F)  338  (°F)    

In‐line P (psi)  150  (psi)    

   Cyclone Differential Pressure  3.3  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

30.3  % start    

16.1  % end    

     

                          

93

Table E-16: Trial 11 Supplemental Data

Trial #  11     Date  3/10/2009          

% Starch  20  % w/w    

Volume  200  mL    

Theoretical Starch  50  g    

Actual Starch  50.0169  g    

Feed T  170  (°C)  338  (°F)    

Flow Rate  7.5  Hz    

Drying  T  200  (°C)    

     

     

Oil T Set Point (°C)  189.5  (°C)  Inlet Fan  25.75  Hz 

Oil T Operating (°C)  189.5  (°C)  Exhaust Fan  38  Hz 

   Chamber Pressure ‐0.21 to ‐0.4  mbar 

In‐line T (°F)  338  (°F)    

In‐line P (psi)  165  (psi)    

   Cyclone Differential Pressure  3.2  mbar 

   Feed Pressure  7.91  bar 

Relative Humidity 

20.2  % start    

28  % end