Functional Properties of Coconut Protein and Its Role on Emulsion Stability of Coconut Milk Products

Mr. Ekasit Onsaard 4483011

Department of Food Technology, Graduate School, Prince of Songkla University

Thesis Proposal

Advisory Committee: Dr. Manee Vittavanont Assoc.Prof.Dr. Sukoncheun Srigam Assoc.Prof.Dr. David Julian McClements Prof.Dr. Eric A. Decker

Scope

Introduction Objective Scope of the

research Materials and

methods Expected outcome Research plan

Introduction

Coconut

Figure 1 Cross section of a coconutSource: Canapi, et al. (1996)

Coconut Meat

Table 1 Proximate composition of mature coconut kernel meat

Source: Modified from Dendy and Timmins (1973); Grimwood (1975); Balachandran, et. al. (1985); Chakraborty (1985); Kwon et al. (1996)

Utilization of coconut meat

Coconut milk

Coconut oil

Oil extraction

Fresh coconut meat

(2) hydraulic press

Coconut milk centrifuge

Cream Skim milk

Protein isolate

Water Oil Protein Protein concentration

(1) Dried coconut meat (copra) mechanical press

Oil Coconut meal

Protein isolate

Coconut milk

The term “Coconut milk” is referred to a white, opaque protein-oil-water emulsion obtained by pressing

grated solid coconut endosperm with or without addition of potable water or liquid

endosperm (Seow and Gwee, 1997).

Weak Point - Short-term physical and microbial stability

Thermal processing of coconut milk products

Pasteurization Sterilization UHT

Problems

Emulsion instability

Objectives

1. To investigate type, characteristics and proportion

of coconut proteins in coconut meat and

coconut milk 2. To evaluate functional properties of major protein

fractions in coconut milk

3. To study role of main coconut proteins on emulsion stability of thermally processed

coconut milk products

Scope of the Research

In this research project, coconut proteins will be extracted and fractionated from coconut meat and coconut milk. Then their type, proportion, physicochemical characteristics, and functional properties will be investigated. The roles of main protein fractions and some factors affecting on emulsion stability of thermally processed coconut milk will be examined in a model system.

Materials

The mature coconut (11-13 month) used as a source of coconut meat throughout this

research is a native coconut palm variety, which is grown in Thanam district, Pattani province.

Coconut samples

(1) All chemicals used in analytical method are analytical grade.

(2) Chemicals used as solvent for oil extraction from coconut meat are commercial grade.

Chemicals

Part I

1. Study on characteristic and chemical compositions of coconut meat and coconut milk

1.1 Preparation of coconut meat, coconut milk, coconut cream, and coconut skim milk

1.2 Physical properties and chemical composition of coconut meat and coconut milk.

Methods

2. Study on types and proportion of coconut protein in coconut meat, coconut cream and

coconut skim milk 2.1 Preparation of coconut cream protein;

CCP 2.2 Preparation of coconut skim milk

protein; CSP 2.3 Types, concentration and proportion of

each protein fractions in coconut meat, coconut cream and coconut skim milk

1.1 Preparation of coconut meat, coconut milk, coconut cream, and

coconut skim milk

(1)

1. Study on characteristic and chemical compositions of coconut meat and coconut milk

(2)

(3)

1.2 Physical properties and chemical composition of coconut meat and coconut milk

(1) Coconut meat (section 1.1(1))

- protein, fat, moisture and ash (AOAC,1999)

(2) Coconut milk, coconut cream and coconut skim milk

(section 1.1(2) and 1.1(3)) - pH (pH meter)

- Viscosity (Brookfield viscometer) - Fat (Mojonnior Ether Extraction; AOAC,1999)),

protein, moisture and ash (same method in 1.2(1))

2. Study on types and proportion of coconut protein in coconut meat, coconut cream and coconut skim milk

Coconut milk and coconut cream will be used to prepare CCP by

two methods as follows:

(1)

2.1 Preparation of coconut cream protein; CCP

(2)

CCP will be freeze-dried and analyzed for content of protein, fat, moisture, and ash. CCP will be kept

at -200C until further used for protein fractionation.

2.2 Preparation of coconut skim milk

protein; CSP Coconut skim milk will be filtered

through 0.45 m by microfiltration. The CSP will be concentrated and isolated as follows:

(1)

(2)

The CPC and isolate will be freeze-dried and analyzed for the content of protein, fat, moisture and ash.

  2.3  Types, concentration and

proportion of each protein fractions in coconut meat, coconut cream

and coconut skim milk Defatted coconut meat (1.1(1)), CCP (2.1) and CSP (2.2) will be extracted and fractionated using method used by Kwon et al., (1996).

3. Study on characteristics and functional properties of coconut proteins

3.1 Characterization of coconut proteins3.2 Determination of functional properties of coconut proteins

Part II

3. Study on characteristics and functional

properties of coconut proteins

3.1.1 Molecular weight of coconut proteins- Size exclusion chromatography (Hagenmaier et al., 1972a)- Sodium dodecyl sulfate polycrylamide gel electrophoresis

(SDS-PAGE) (Laemmli, 1970)3.1.2 Isoelectric point; pI (Isoelectric Fousing Electrophoresis;

IEF)3.1.3 Thermal denaturation behavior (Differential scanning

calorimetric; DSC)3.1.4 Amino acid profile (Kwon et al., 1996)

3.1 Characterization of coconut proteins Some important physico-chemical

characteristics of the CCP (2.1), CSP(2.2) and each protein fraction of coconut meat, CCP and CSP fromsection 2.3 will be determined as follows:

3.2 Determination of functional properties of coconut proteins

Some functional properties of CCP, CSP and their main protein fractions will be determined within pH condition range from 4-7 and NaCl concentration of 0-2.5 M.

3.2.1 Solubility (Chobert et al., 1988)3.2.2 Emulsifying properties

- Emulsion capacity (Wang and Kinsella, 1976)

- Emulsion activity (Pearce and Kinsella, 1978)

- Emulsion stability (Chobert et al., 1988)

3.2.3 Gelling properties - Least gelling concentration- Gelling temperature (gelling

point) (Rheometer) 3.2.4 Water holding capacity;WHC

(Tomotake et al.,2002) 3.2.5 Fat absorption capacity; FAC

(Tomotake et al.,2002)

4. Study on the role of main protein fractions of coconut milk and the effect

of heat treatment on emulsion stability of coconut milk model system

4.1 Preparation of a model system of coconut milk emulsion 4.2 Effects of type, proportion and concentration of main protein

fractions of coconut milk on emulsion stability of coconut milk in model

system 4.3 Effects of heat treatment at various levels on emulsion stability of coconut milk in model system

Part III

4. Study on the role of main protein fractions of coconut milk and the effect of heat treatment on emulsion stability of coconut milk model system

4.1 Preparation of a model system of coconut milk emulsion

Physical properties of coconut milk model system

and coconut milk containing the same

protein and fat content, and pH value will then be

determined as follows: - Emulsion stability;ES (Dagorn-Scaviner et al., 1987)

- Droplet size and distribution (laser light scattering) - Viscosity (Brookfield viscometer)

Main protein fractions of CCP and CSP from section 2.3 will be used throughout

this study as follows:

4.2 Effects of type, proportion and concentration of main protein fractions of coconut milk on emulsion stability of coconut milk in model system

  (1)   Coconut milk containing various type of predominant fractions of CCP and

CSP will be prepared with the same procedure as 4.1. Physical properties of the obtained coconut milk will be determined

by the same method used in 4.1 in comparison with the standard coconut milk

model system.

  (2) Coconut milk containing mixture

of main fractions of CCP/CSP at various proportions will be prepared with the same procedure as 4.1. Physical properties of the

coconut milk model systems will be determined by method used in 4.1 and compared with the

standard coconut milk model system.

The adequate proportion of main fraction of CCP/CSP that gives the highest stability will be chosen for further study in section 4.2 (3).

(3) The coconut milk model system containing a proportion of

CCP/CSP chosen from the 4.2 (2) will be prepared in various total protein concentration. Physical properties of the coconut milk model system will then be determined by the same method in 4.1 in comparison with the standard coconut milk model system.

The total protein concentration level that gives the highest stability will be chosen for study in section 4.3.

4.3 Effects of heat treatment at various levels on emulsion stability of coconut milk in model system

5. Experimental Design and

Statistical Analysis

All analysis and measurement will be performed in at least three replicates. The experimental design for section 3.2 and 4 will be a completely randomized design (CRD). Data will be analyzed by the analysis of variance (ANOVA) and mean comparison will be carried out by Duncan’s multiple-range test at P < 0.05 using SPSS software version 10.0.

Expected outcome

The first part of the project will provide information about types, proportion and characteristics of proteins in coconut meat and coconut milk. It will be used to design a model system of coconut milk for investigating coconut proteins on emulsion stability of coconut milk.

The important functional properties of major protein fractions will be obtained from the second part of the experiment. The information will indicate the potential use of coconut proteins as a new functional ingredient in food industry.

In the last part, role of coconut proteins (type, proportion and concentration) on stability of fresh and thermal processed coconut milk will be revealed. The knowledge gained is expected to be useful as a direction for development of stable thermally processed coconut milk products.

Expected outcome (cont.)

6. Research plan