PHYSICO-CHEMICAL CHARACTERIZATION OF NATIVE AND ACID-ALCOHOL (NITRIC ACIDMETHANOL) MODIFIED POTATO STARCHES AND THEIR COMBINATIONS IN DIFFERENT PROPORTIONS

Abstract

The potato starch was extracted and chemically modified using nitric acid in methanol at 35˚C. Mixtures were formulated by adding chemically modified starch to the native starch at different levels viz. 0, 10, 30, 50, 70, 90 and 100%. The swelling power of the starches decreased as the level of incorporation of modified starch increased and ranged between 18.72 to 0.77 g/g, while the solubility increased and ranged between 7.03 to 88.77%, at 90˚C. The amylose was observed to decrease significantly (p less than 0.05) from 24.55 to 3.26% upon modification. The granular morphology of potato starches as observed by scanning electron microscopy revealed partial protuberances upon modification. Analysis of X-ray diffractograms showed B-type crystalline structure of potato starch, which did not change upon modification, however, the sharper peaks of modified starch indicated increase in the relative crystallinity. A significant (p less than 0.05) increase in light transmittance upon acid-alcohol modification was observed which decreased on refrigerated storage. These mixtures of native and modified potato starches differ significantly (p less than 0.05) in their physico-chemical properties, thus starches with required functionality can be produced by mixing native and modified starches in suitable proportions.