Effect Of Steeping Period On Yield And Acceptability Of Starch
Extracted From Sorghum (Sorghum Bicolor, White Variety And Red
Variety)
TABLE CONTENTS
Title Page
Approval Page
Dedication
Acknowledgement
Abstract
Table of contents
CHAPTER ONE
1.0
Introduction
1.1
Statement of Problem
1.2
Objectives of the Study
CHAPTER TWO
2.0
Literature Review
2.1
Origin of Sorghum
2.2
Structure of Sorghum
2.3
Nutritive Value
2
2.4
Uses and Method of Preparation
2.5
Limitation / Toxicity
2.6
Processing of Sorghum for Starch
2.7
Starches
2.7.1 Definition
2.7.2 Forms / Structures / Derivatives
2.7.3 Reactions of Starch in Food Systems
2.7.4 Food Uses of Starch and their Functional Properties
2.7.5 Spoilage of Starches
CHAPTER THREE
3.0
Materials and Method
3.1
Source of Raw Material
3.2
Method of Production
3.3
Analysis of Some Functional Properties
3.3.1 Determination of Yield
3.3.2 Bulk Density
3.3.3 Syneresis
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3.3.4 Swelling Capacity
3.3.5 Gelation Temperature
3.3.6 Least Gelation Concentration
3.4
Metabolisable Energy Value
3.5
Glycosidic Cyanide Content
3.6
Moisture Content
3.7
Sensory Evaluation
CHAPTER FOUR
4.0
Results / Discussion
4.1
Results
4.2
Discussion
CHAPTER FIVE
5.0
Conclusion and Recommendation
References
Appendix
CHAPTER ONE
4
1.0
INTRODUCTION
Starch is non-crystalline white powder, insoluble in cold water.
It can be hydrolysed into simpler molecules by either heating with an acid or a
suitable enzyme. (Awan and Okaka, 1983).
Starch is the major storage form of carbohydrate in sorghum and millets. It
consists of amylopectin, a branched – chain polymer of glucose, and amylose,
a straight chain polymer (FAO, 1992).
The digestibility of the starch, which depends on hydrolysis by
pancreatic enzymes, determines the available energy content of cereal grain.
Processing of the grain by methods such as steaming, pressure cooking,
flaking, puffing or Micronesian of the starch increases the digestibility of
sorghum starch.
This has been attributed to a release of starch granules from the protein
matrix rendering t hem more susceptible to enzymatic digestion (FAO, 1992).
When starch is heated in water (moist heat) it will produce a gel – an
important property needed in the thickening of gravies, sauces, in the baking of
bread and production of custards (Awan and Okaka, 1983).
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The physico-chemical properties of the starch affect the textural
characteristics of the food preparations made from the grain.
The behaviour of starch in water is temperature and concentration
dependent (Malleshi and Desikachar, 1985).
Starches in general show very little uptake of water at room temperature
and their swelling power is so small. At higher temperature, water uptake
increases and starch granules collap--- which leads to solubilisaiton of amylose
and amylopectin to form a colloidal solution. This is the gelatinisation stage.
Genetic and environmental factors affect the gelatinisation temperature of
starch (Freeman and Bocan, 1973).
Heat treatment of starch in a limited amount of water lead to swelling the
granules with very little loss of soluble material and partial gelatinization of
the starch (Watson, 1970).
On cooking, the gelatinized starch tends to return from the soluble,
dispersed and amorphous state to an insoluble crystalline state.
This phenomenon is known as retrogradation or set back; it is enhanced
with low temperature and high concentration of starch (Rooney, 1991).
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Amylose, the linear component of the starch, is more susceptible to
retrogradatioln than the amylopectin (Freeman and Bocan, 1973).
1.1
STATEMENT OF THE PROBLEM
Steeping of sorghum for a longer period consumes time and imparts
undesirable flavour to the starch extracted from the sorghum due to the action
of some spoilage microorganisms. Hence the need to reduced the steeping time
and detect its effect on the yield and their sensory properties.
1.2
The overall objective of the project work is to develop a process for
extracting starch from two different cultivar of sorghum by subjecting to
different steeping time.
The null hypothesis is that cultivar and steeping period will not have
effect on the yield and functionality of the extracted starch.
Specific aims are:
To determine the effect of steeping period on:
1.
The yield of the starch
2.
The functional properties of the starch
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3.
Organoleptic properties of the starch
4.
The glycosidic cyanide level of the starch
5.
The metabolysable energy value of the starch
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