Sorption properties of modified potato starch

Background. Starch is one of the biopolymers most commonly used in the food industry. In its native form its applications are limited. In contrast, its structure is relatively readily modified using various methods, producing starch derivatives of greatly diverse properties. The primary methods used to change characteristics of starch include acetylation and oxidation. Thus obtained raw materials are used as food additives. Stability of these raw materials and food products to a considerable extent depends on their composition and parameters characterizing storage facilities, i.e. relative humidity and temperature. One of the methods to specify adequate ambient conditions is based on water activity supplemented by sorption isotherms. As a result studies investigating correlations between water activity and moisture content are of importance for the optimization of storage conditions and design of certain food processing procedures. For this reason the aim of this study was to assess the effect of modification (oxidation, acetylation and their combination) on sorption properties (described based on sorption isotherms) of potato starch. Material and methods. Analyses were conducted on potato starch and its derivatives produced by acetylation, oxidation and co-modification (acetylation coupled with oxidation). Starch was oxidized using sodium chlorate (I), while acetylation was run using anhydrous acetic acid. Sorption isotherms were determined by the static desiccator method. Results were described applying selected mathematical methods equipped with physical interpretations (BET and GAB) and empirical models (Halsey, Oswin, Henderson, Pelega, Lewicki, Blahovec-Yanniotis). Calculations were made using non-linear estimation.