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PRODUCTION OF STARCH FROM CASSAVA (Maihot esculanta) AND ITS CROSS LINKED DERIVATIVES
CHAPTER ONE
1.0 INTRODUCTION
Starch can be obtained from cassava, sorghum, maize, sago and potatoes. But this project focused on the production of starch from cassava. Starch can be cross-linked a product that will be suitable for noodle, salad cream custard making. Normally it is easier to make this product from corn and potatoe starch, but cassava which is readily available and cheap can be employed to meet the demand of the people.
Other synthetic starch produced from cassava includes; carboxymethyl starch (which is produced when one of the hydrogen atom of the starch is replaced by carboxymethyl groups, starch acetate, starch xanthate and hydroxyl alkyl starch. These are used as thickening agents, sterbilizer and emulsifier in products. Cassava starch when treated with phosphate are used in frozen products when they are defrosted to prevent them from dripping. This study investigated the production of starch from cassava and preparation of cross-link derivatives.
LITERATURE REVIEW
1.1 MEANING AND COMPOSITION OF STARCH
Starch is one of the most abundant substances in nature, a renewable and almost unlimited resource with a chemical formula (C6H10O5)n. It is a polysaccharide, a chain of many glucose molecules. It is the most carbohydrate stored in roots and seeds of plants.[1] There are two types of glucose chain in starch which are the amylose and amyloeptin.
1.2.1 COMPLEX BRANCH CHAIN (AMILOPECTIN)
Amylopectins are made up of several million glucose units. It forms branched structures with about 30 glucose units in a chain between branches. This makes the molecule somewhat stripped in appearance with the knotted branch point in all rows and smooth chain separating them. These molecules are so large that this stripped appearance show up under a light microscope forming what appears to be ‘growth rings’ in the starch grain.[2]
1.1.2 AMYLOSE CHAIN
Amylose chain tend to curl up into tielice (spirals) with the hydrophobic part inside. This allows them to trap oil and fat inside the helix as well as aroma molecules.[2]
WHAT IS GELATINIZATION?
This is a colloidal structure that is, it has interparticle bonds (usually hydrogen bonds) or lower potential energy than starch in true solution[3].
Starch gelatinization is a process that breaks down the intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding and oxygen sites (the hydroxyl) to engage more water. This irreversibly dissolves in starch granules. Penetration of water increases randomness in the general granule structure and decreases the number and size of crystalline regions [4]. Hence crystalline region do not allow water entry. Heat causes such region to be diffused so that the chain begin to separate into an amorphous form. This process is used in cooking to make roux sauce, pastery custard or popcorn.[5]