Hydration level significantly impacts the freezable - and unfreezable -water contents of native and modified starches

Kamil Emre Gerçekaslan

doi:10.1590/fst.04520

Abstract

Abstract The freezable- and unfreezable-water contents of corn and waxy corn starches (native, pregelatinized and retrograded) were analyzed at various hydration levels (25, 35, 45, 55, 65, 75, 85%) using Differential Scanning Calorimetry (DSC). The unfreezable water contents and also the temperature of onset (To), peak (Tp) and endset (Te) of the peaks' in all samples were increased with increasing hydration level. Water absorption index (WAI) and water solubility index (WSI) values of the pregelatinized and retrograded starch samples were significantly higher (p<0.05) than their native counterparts. RVA profiles revealed that modified starches had higher viscosity values than natural starches.

Highlights

Starch is being widely used in the production of many food substances but it is sought by the pharmaceutical industry, textile, paper industry, alcohol-based fuels and adhesives (Kaur et al, 2012; Fu et al, 2014)
Obtaining higher initial viscosity values in physically modified waxy corn starches is due to the fact that amylopectin in the starch molecule is the main component responsible for swelling of starch and the physical modifications promote this swelling
The highest Water absorption index (WAI) and water solubility index (WSI) were obtained in the pregelatinized waxy corn starch samples

Summary

Introduction

Starch is being widely used in the production of many food substances (soups, salad dressings, bakery products, milk puddings, snacks, coatings, meat products) but it is sought by the pharmaceutical industry, textile, paper industry, alcohol-based fuels and adhesives (Kaur et al, 2012; Fu et al, 2014). The chemical and physical features of starches affect the texture, viscosity, gel structure, stickiness, binding ability, water holding capacity and homogeneity of the products where they are used. These functional properties of the starch vary with the amylose-amylopectin content. Amylose/amylopectin ratio as well as branching density of starch impact its functional properties. High levels of chain branching improve of the solubility of starch while delay gel formation (Kohyama et al, 2004; Sasaki, 2005; Sajilata et al, 2006; Kaur et al, 2012). The granule type of starch significantly impacts its functional properties such as water solubility, hydration temperature and swelling indexes

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