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CHAPTER 2

REVIEW OF RELATED LITERATURE

2.1 Coconut

The coconut palm, Coco Nucifera L., is a member of the family Arecaceae. The

term coconut can refer to the entire coconut palm, the seed, or the fruit, which

botanically not a nut but a drupe. The fruit is harvested for its white flesh, husk, and

coconut water (Lerner, 2007). It is cultivated for its various benefits, namely nutritional,

medicinal advancement against diseases and for the development of industrial products

(Mandal, 2011).

The coconut takes between 11 and 12 months to reach full maturity. At five

months, the kernel begins to form a thin layer of jelly around the inside of the endocarp

or shell. The shell encloses the tender water, a clear sweet liquid (Prades, et al., 2011).

Coconut is a fruit in which an outer skin (exocarp) and fibrous husk (mesocarp)

surrounds a hard husk (endocarp) with a coconut meat (endosperm) inside (Armstrong,

2008). Coconut fruit is shown in Fig.2.1.

Figure2.1 Coconut Fruit

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The production of coconut shows a significant role in the economy of the

Philippines. Being the worlds largest producer of coconuts, an average of 2.712 million

metric tons of said products were harvested in medium-sized farms in year 2009 up to

2012 as shown in Table 2.1 (FAO, 2011).

Table 2.1 Production of Coconut in year 2008-2012

(Source: Philippine Coconut Authority)

2.1.1 Coconut water

Coconut is unique among other fruits because it contains a large quantity

of liquid. When it has not yet reach full maturity they are called tender coconut

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water which can be harvested for drinking. Coconut water in its natural form is

recognized as a refreshing drink. Popularity of this drink is increasing due to its

good nutritional value, low calorie and free from added ingredients (Paniappan,

2012).

Tender coconuts after removing from the tree can be kept for 15 days

without spoilage in ambient conditions (Chandy, 2009). Once opened the

coconut water becomes off-flavored in taste and turns sour due to intense

enzymatic activity (USDA, 2009).

Coconut water became a popular drink in thetropics,especially inIndia,

Africa, Caribbean and here in the Philippines. It is presented in the market fresh,

canned, and bottled. It has a shelf life of 24 months when placed in bottles

(Belargo, 2010).

2.1.1.1 Benefits and Composition

Coconut water contains antioxidants, vitamins and minerals,

sugar, proteins, dietary fibre and provides an isotonic electrolyte balance.

The biologically pure, coconut water helps to replace fluids, electrolytes

and sugars lost from the body during heavy physical activities (Fife,

2008). This natural drink is believed to be useful in preventing and

relieving many health problems including dehydration, constipation,

digestive disturbances, malnutrition, fatigue, heatstroke, boils, diarrhea,

http://en.wikipedia.org/wiki/Tropicshttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Tropics

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kidney stones, osteoporosis, urinary tract infections, and sterility (Fife,

2008).

Table 2.2 below shows that coconut water is also rich in many

essential amino acids including lysine, cystine, phenylalanine, histidine,

and tryptophan (Gopikrishna, 2008).

Table 2.2 Composition of tender coconut water

(Source: Journal on Quantitative Analysis of Coconut water)

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2.1.1.2 Nutritional Contents

This Table 2.3 shows nutrition value per 100 grams (g) of tender coconut

water. It reflects available nutrition facts, vitamins, electrolytes, minerals and its

nutrient value and percentage recommended dietary allowances.

Table 2.3 Nutrition Value per 100g of Coconut Water

PrincipleNutrient

Value

Percentage of

RDA

Energy 19 Kcal 1%

Carbohydrates 3.71 g 3%

Protein 0.72 g 1.5%

Total Fat 0.20 g 1%

Dietary Fiber 1.1 g 3%

Vitamins

Folates 3 g 0.75%

Niacin 0.080 mg 0.5%

Pantothenic acid 0.043 mg

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Minerals

Calcium 24 mg 2.4%

Copper 40 mcg 4.5%

Iron 0.29 mg 3.5%

Magnesium 25 mg 6%

Manganese 0.142 mg %

Zinc 0.10 mg 1%

(Source: USDA National Nutrient data base)

2.2 Membrane Technology

Membrane technology is used in the beverage industry especially in clarification

of fruit juice. Membranes range from finely porous structures to nonporous and can

remove contaminants such as bacteria and protozoa down to ions (Wang 2013). In last

two decades, there has been a significant growth and increase in its application.

Membrane technology has full scale global applications in municipal and industrial

wastewater, ultra-pure water, speciality chemicals, recovery/reuse, agriculture,

pharmaceutical, power generation, drinking water and beverages (AMTA, 2007).

There are four levels of membrane filtration. These levels are from largest to

smallest pore size namely microfiltration, ultrafiltration, nanofiltration, and reverse

osmosis. This table also enumerates particular target contaminants from 1 m to 0.001

m that are being removed in different filtration level (Dave, 2013).

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Table 2.4 Comparison of Membrane Filtration Levels

(Source: Virginias Community College)

2.2.1 Microfiltration

Microfiltration (MF) is a type of physicalfiltration process where a

contaminated fluid is passed through a specialpore-sized membrane to

separatemicroorganisms and suspended particles from processliquid (Baker,

2012).

Microfiltration can be an alternative to fruit juice preservation and

conservation, because it does not involve the use of heat treatment since thermal

processes largely affect the characteristics of fruit juices. The advantages of

microfiltration are the use of mild temperature and pressure conditions, which

maintain the nutritional quality and the sensorial attributes of the products

(Carvalho, 2010).

http://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Porosityhttp://en.wikipedia.org/wiki/Microorganismshttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Microorganismshttp://en.wikipedia.org/wiki/Porosityhttp://en.wikipedia.org/wiki/Filtration

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2.2.1.1 Dead-End Filtration

In dead-end filtration, the feed flow perpendicular to the

membrane. The particulates will accumulate and form a cake at the

membrane surface. The cake increases in height throughout the filtration

period resulting in a decrease in permeate flux (Fumatech, 2010).

Therefore the membranes in dead-end operations have to be cleaned at

regular intervals either by backwashing or other physical cleaning

methods (Lenntech, 2009).

2.2.2 Ceramic Filter Cartridge

In 1846, Henry Doulton has invented the modern form of ceramic that was

widely recognized as a premier manufacturer of an effective prevention device

for treating infective water. Doulton's original organization for water filters

remains in existence, although it has been sold and renamed several times

(Berks, 2008). As with most filtration methods, fluid stream is carefully introduced

to one side of the filter, which acts to block the passage of anything larger than

the pore size.

Ceramic filters are inexpensive and effective type of filter that rely on the

small pore size of ceramic material to remove dirt, debris, bacteria, protozoa, and

microbial cysts but are not effective against viruses since they are small enough

to pass through. The major risks to the success of all forms of ceramic filtration

are hairline cracks and cross-contamination (Brown et.al, 2011). In comparison to

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polymeric membranes, ceramic membranes are slower to foul and can be

regenerated using more extreme membrane performance recovery methods,

which polymeric membranes are unable to handle due to thermal limitations of

polymeric materials (Panglisch, 2009).

2.2.3 Permeate Flux

Permeate flux is usually analyzed by the decline in flux and the decrease

of transmission over time resulting to the reversible accumulation of particles on

the membrane surface, which eventually progresses to the irreversible cake

build-up (Hwang, & Liao, 2011).

Permeate flux may change with filtration time according to the fouling

behaviour of the feed solution. High initial permeate flux followed by a rapid flux

decrease is characteristic of constant TMP operations. The initial high increase of

pressure cause rapid particle deposition which results in a fast build-up of a

boundary layer at the membrane surface (Buetehorn et al., 2012). Permeate flux

during a microfiltration process of pineapple juice is illustrated in Fig.2.2.

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Figure 2.2 Permeate flux during a microfiltration process of pineapple juice

This graph showing filtration of pineapple juice is a typical example of

permeate flux during a microfiltration process. There is a decline of the permeate

flux attributed to fouling due to pore blocking and cake built up (Yasan et al.,

2007).

2.2.4 Membrane Fouling

Membrane fouling is accumulation of non-dissolved material that is either

deposited on the pore mouths or walls of the membrane. Fouling leads to an

increase in resistance giving less flux for a given vacuum pressure difference.

For example, using a metering pump to maintain a fixed permeate flow rate.

Understanding the other resistances is important and it is imperative to

distinguish a reduction in driving force across the membrane from an increase in

resistance because of fouling of the membrane (Field, 2010).

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Membrane fouling can be classified as physically reversible or irreversible

fouling. Physically reversible fouling can be eliminated totally by physical

cleaning or certain pretreatment while physically irreversible fouling can be

overcome by chemical cleaning limited to a minimum frequency since repeated

chemical cleaning may affect membrane life (Hiroshi et al., 2007).

2.2.5 Transport Phenomena in Membrane Processes

In membrane processing, the external pressure that must be applied for

significant permeate flux must be higher than the osmotic pressure of the

solution. The basic relationship between applied pressure (by a pump), osmotic

pressure, and flow of solvent through a membrane is expressed in terms of the

flux and the driving force and resistances. Eqn1. is for an ideal semipermeable

membrane:

Eqn.1

Where J is the flux, A is a membrane permeability coefficient, PT is the

transmembrane pressure, and is the osmotic pressure of the feed solution.

For an ideal membrane and feed solution the Eqn.1 is rewritten given by Eqn.2

Eqn.2

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Where A is a membrane permeability coefficient, and is the viscosity of

permeate. For a particular feed solution at a given temperature, viscosity is

usually included with the A value and can written as

which is rewritten below

in Eqn.3 where is the intrinsic membrane resistance determined using pure

water as the feed.

Eqn.3

In actual operation with a real feed, the membrane resistance may be only

a small part of the total resistance.

Eqn.4

If significant membrane fouling occurs because of specific membrane-

solute interactions, the intrinsic membrane resistance may change based on the

Eqn.4. It is accounted for by adding another resistance term, RF because of

fouling to the model (Cheryan, 1989).

2.2.6 Cleaning Process

The cleaning process is just as important as the actual filtration process.

It is fundamental in determining the technical and economic viability of the

processes on an industrial scale where efficiency and repeatability are essential

(Coutinho, 2009). Membrane cleaning methods can be divided into physical,

chemical and physio-chemical. In practice, physical cleaning methods followed

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by chemical cleaning methods are widely used in membrane applications (Arnal

et al., 2011).

In general, acids namely nitric, phosphoric, hydrochloric and sulphuric are

often used to remove precipitated salts or scalants, while alkaline cleaning is

suitable for organic fouling removal. Other categories of chemical cleaning

agents are metal chelating agents, surfactants and enzymes (Mohammadi et al.,

2007).

2.2.7 Backwashing

Backwashing is a type of cleaning method that uses reverse mechanism

of filtration process wherein the suction pressure is applied on the retentate side.

The accumulated cake flushed out from the membrane pores. The pressure on

the permeate side of the membrane is higher than the pressure within the

membranes, causing the pores to be cleaned. Many techniques have been

developed to overcome fouling. Backwashing is typically used to clean

membranes, while more persistent foulants are removed by the use of chemical

reagents. However, these chemicals sometimes damage the membrane

materials reducing the lifetime and efficiency of the membrane and even cause a

secondary pollution over cleaned membrane (Arnal, 2011). Fig.2.3 shows the

cleaning flow direction in backwashing.

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Figure 2.3 Backwash Mechanism

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CHAPTER 3

RESEARCH METHODOLOGY

3.1 Materials and equipment

Coconuts with maturity of 6-7 months, shown in Figure 3.1, were harvested from

the province of Famy, Laguna.

Figure 3.1 Raw material used in the study: Coconut fruit

Laboratory instruments used in the preparation of the solutions needed for the

tests were hot plate model design by company Corning, analytical balance model, pump

set up fabricated by Schuco Inc. Model 5711 130 including the vacuum receiving

container and basic instruments like beaker, flasks, cylinder and stirrer. The

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microfiltration apparatus was supplied by the company Osmosis. The ceramic filter

cartridge, with a 0.3-0.9m pore diameter, was manufactured by MegaFresh Company.

3.2 Preparation of the Reagents

3.2.1 Dilute bleach solution

The dilute bleach solution was prepared by dissolving 300ppm or one (1)

tablespoon of bleach into 4.5 liters of water. The solution was used for the

sanitization of the coconuts (Rolle, 2007).

3.2.2 Preparation and Standardization of 0.1M NaOH

A 0.1 molar sodium hydroxide (NaOH) solution was prepared by weighing

4.00 grams of NaOH pellets supplied by Lab-Scan Analytical Sciences Asia Co.

Ltd. Using a 250 mL beaker, the pellets were dissolved in a 200 mL of warm

freshly boiled deionized water. The deionized water was supplied by

Pharmacology Laboratory, Room 307, Thomas Aquinas Research Center

(TARC). The beaker was covered with a plastic film and was cooled to room

temperature. Using a volumetric flask, the same freshly boiled distilled water was

added to the solution until a volume of one (1) L was achieved. Four (4) liters of

0.1M NaOH solution was prepared during the experiment.

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3.2.3 Preparation of 0.1M H2SO4

Sulfuric acid is corrosive and obtaining 10 mL needed for the preparation

was done under the fume hood. The 10 mL sulfuric acid was obtained using

graduated cylinder. The acid was then poured into a 1 L of deionized water and

was stirred. The acid prepared was 1% v/v sulfuric acid. Four (4) liters of 0.1M

H2SO4solution was prepared during the experiment.

3.3 Extraction of Coconut Water

3.3.1 Good hygienic practices

The persons involved in the sanitation and extraction of the coconut water

observed good hygienic practices. The washing of hands before and after every

process was strictly observed. All laboratory glass wares were properly cleaned

and dried. Laboratory gowns, masks and gloves were used at all times during the

experimental proper (Rolle, 2007).

3.3.2 Sanitization of the coconut

The coconuts were washed and brushed using potable running water to

thoroughly remove dirt and debris of any form on the surface of the coconut

husk. Damaged coconut and those with visible cracks were discarded. The

water-washed coconuts were then soaked into the dilute bleach solution for 15

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minutes to reduce the number of microorganisms on the surface of the nut. Then,

the clean nuts were allowed to air dry in a clean surface (Ohler, 1999).

3.3.3 Sanitization of chopping board and bolo knife

The chopping board was thoroughly scrubbed using antibacterial

dishwashing liquid. Dirt and sand traces were also removed using a scrubber.

The chopping board was soaked in the bleach solution for 15 minutes. The bolo

knife was newly bought and cleansed thoroughly using scrubber to remove

traces of rust and dirt. Then it was soaked in the bleach solution for 15 minutes.

The tools were rinsed with running water for five (5) minutes and then air-dried.

3.3.4 Coconut water extraction and pre-filtration

All tools were properly sanitized and air-dried in order to reduce microbial

contamination. Sanitation of the tools and glass wares were done by soaking

them into boiling water for 15 minutes and were dried at ambient air condition.

Small hole was pierced at the surface of the coconut using the bolo knife. The

coconut water was coarse filtered using sanitized filter cloth (cheese cloth) to

remove solid particles and coconut kernels and stored in sanitized containers.

According to the Philippine Coconut Authority (PCA), the average volume

of fresh coconut water per nut is 300 mL. Sixty (60) coconuts were extracte

during this experiment having an approximate of 18 liters of fresh coconut water.

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Figure 3.2 Microfilter Equipment

3.4 Cleaning of Microfilter equipment

Contaminants were removed with proper cleaning. Three steps were done to

avoid the contamination of the coconut water during filtration. This includes the running

of deionized water, caustic solution followed by the acid. The alkali used has a molarity

of 0.1 NaOH solution and the acid cleaning by 1% v/v sulfuric acid solution of pH 4. The

acid and alkali solutions were circulated in the equipment for 20 minutes then rinsed

again with deionized water to remove the residues. The whole process was roughly

done within 1 hour and 30 minutes.

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3.5 Microfiltration

3.5.1 Membrane Material

The feed was microfiltered at constant vacuum pressure of 21 inHg on

each trial using 0.3-0.9 m pore ceramic membrane manufactured by MegaFresh

Co., Ltd. The membrane used has a property of being unreactive to chemicals

because it consists of titania, zirconia and alumina. It was compatible with all

solvents, acids and alkaline solutions (Csem, 2010). The dimension of the

ceramic membrane is 9.093 inches (23.0962 cm) length and has a diameter of 2

inches (5.08 cm). The effective surface area of the filter is 57.1330 in 2(0.03686

m2). Clean membrane was used for every run in the experiments. After each run,

the membrane was cleaned and kept in a sealed container soaked in bleach

solution to avoid bacterial contamination.

3.5.2 Microfiltration Set-up

The experiment was done using Lab-scale water filtration apparatus,

which was fabricated by the company Osmosis. A centrifugal pump with a

constant suction pressure of 21 inHg was observed in the experiment. The

vacuum pressure was maintained constant and measured by a pressure gauge

directly attached to the pump. Permeate was collected by a receiving container

under vacuum condition. The time of permeate collection was expected to be

non-linear and may vary in each trial.

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3.5.3 Procedures in Assembling the Microfiltration Set-up

3.5.3.1. All materials and equipment should be sanitized by the

prescribed procedures. It will be followed by air-drying at ambient

conditions to avoid microbial contamination.

3.5.3.2. The sanitized ceramic filter will be inserted intact in the ceramic

filter casing. Any small holes and misfittings will affect the efficiency of the

membrane.

3.5.3.3. To be able to put the membrane intact, rubber fittings should be

used wrapped in Teflon tape to avoid any pressure that may interfere with

the performance of the pump.

3.5.3.4. The filter casing should be tightly closed after placing the ceramic

filter inside.

3.5.3.5. Connect the suction pump to the receiving flask using clean

rubber tubes. The flask is at vacuum condition. Teflon tape should be

wrapped on the mouth of the container to avoid any pressure

interference.

3.5.3.6. By using clean rubber tubes, connect the different equipments by

following the set-up shown below in Figure 3.3.

3.5.3.7. To assure that there will be no pressure interference in every

tube connections, wrap every end-point of the tubes using Teflon tape.

3.5.3.8. The set-up is dead-end filtration. The efficiency of the filter will be

affected by any pressure interference.

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Figure 3.3 Schematic diagram of the dead-end microfiltration set-up

3.5.4 Water Flux Determination

The deionized water flux was measured after conditioning the

clean membrane to establish the baseline of operation. The water flux

was determined by measuring the volume of permeate obtained for 20

minutes. All the experiments were performed under ambient temperature

and the volume of the deionized water in the feed container was kept

constant to a steady state flow. The resistance to permeation was

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obtained based on the measured clean flux, and from this membrane

resistance will be calculated.

3.5.5 Coconut water microfiltration

The feed was microfiltered under a constant suction pressure of

21 inHg on each trial using 0.3-0.9 m pore size ceramic membrane.

Discharge flow rates were gathered every 250 mL permeate collected

using a receiving flask under vacuum condition. Time was also noted in

every 250 mL increment of discharge permeate. Time was expected to

vary in every trial because of membrane fouling.

3.6 Flux Analysis

For this experiment, time was expected to vary in every trial of filtration because

of membrane fouling. Determination of time when the membrane will be fouled will be

predicted. If the fouling time will be determined, another parameter will be considered,

the back-pulsing or the back wash time. The performance of the ceramic membrane will

also be evaluated if it is applicable for beverage specifically the coconut water.

3.7 Cleaning

Contaminants such as those that foul the membranes can be removed with

proper cleaning of the equipment. To avoid contamination it is required to clean the

system after conducting the experiment. It was carried out in three steps, which typically

include the running of water, caustic solution and then acid. Fouling on the membrane

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surface needs to be removed as effectively as possible after the run. Membrane

cleaning is necessary to keep the membranes in a good condition. Membrane cleaning

is most effective when proper cleaning solution will be applied. High temperature

cleaning solutions will shorten the efficiency and life of the membrane (Global

Membranes, 2012). The alkali cleaning has a molarity of 0.1 NaOH solution and the acid

cleaning by 1% (v/v) sulfuric acid solution. Both solutions used for cleaning were run in

the filtration apparatus for 20 minutes at ambient condition and then rinsed with

deionized water.