Development and Characterization of Biodegradable Films on Native and Esterified Peruvian Purple Yam (Dioscorea trifida) Starches and Tara Gum

The aim was to evaluate if purple yam starch esterification with octenyl succinic anhydride (PYS-OSA) enhances the properties of purple yam starch (PYS)-based films in a blend with tara gum (TG). PYS was isolated from purple yam tubers (PYTs) with distilled water; then, starch was dual-modified by ultrasound (as a pretreatment) and esterification (PYS-OSA). The films PYS:TG and PYS-OSA:TG were characterized through physicochemical and mechanical characterization. The thermal properties (<i>T_o</i>, <i>T_c</i>, <i>T_p</i>, and Δ<i>H</i>) of PYS-OSA decreased in the range of 3.4-7.6% compared to PYS. Fourier transform infrared spectroscopy (FTIR) confirmed esterification, revealing two new absorption bands at 1563.0 and 1726.5 cm^-1, and the degree of substitution (DS) was 0.023. The moisture content and solubility in water were 50.7 and 40.5% greater, respectively, for PYS-OSA:TG films compared to PYS:TG ones, but both films exhibited similar optical properties. The tensile strengths of PYS-OSA:TG films were higher than those of PYS:TG ones; however, the elongation at break was lower. PYS:TG and PYS-OSA:TG films were disintegrated by more than 70% after 13 days of being buried in soil. This work contributes to a better understanding of the starch isolated from purple yam tuber, with potential relevance for sustainable packaging applications.