The effect of ethanol precipitation temperature on the physicochemical properties of purple yam (Dioscorea alata L.) starch and its edible film application

Abstract

Starch-based edible films have attracted considerable attention as biodegradable and environmentally friendly packaging materials; however, native starch often exhibits limited mechanical strength and poor barrier properties. Therefore, modification techniques are needed to improve the functional characteristics of starch for edible film applications. This study aimed to evaluate the effect of ethanol precipitation temperatures (50°C, 75°C, and 100°C) on the physicochemical properties of purple yam (Dioscorea alata L.) starch and its application in edible film production. The experiment was arranged using a completely randomized design (CRD) with three precipitation temperature treatments. Modified starch was prepared using the ethanol precipitation method and subsequently used as a film-forming agent. The results showed that the yield of the modified starch ranged from 66.38% to 77.28%. Morphological analysis using scanning electron microscopy (SEM) revealed progressive structural changes in the starch granules, from intact granules at 50°C to partial deformation at 75°C and complete gelatinization at 100°C. These microstructural changes significantly affected the properties of the resulting edible films (p < 0.05). The resulting films had a thickness of 0.20–0.24 mm, transparency values of 5.42–6.41, solubility of 63.17–78.64%, water vapor transmission rates (WVTR) of 3.69–11.08 g/m²·day, and compressive strength ranging from 202.00 to 291.33 gF (equivalent to 1.98–2.86 MPa). Higher precipitation temperatures generally resulted in films with a more homogeneous and compact microstructure, thereby improving barrier performance and mechanical stability. These findings indicate that ethanol precipitation modification can enhance the functional properties of purple yam starch and supports its potential application as an edible and biodegradable film for sustainable food packaging.

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