Autoclaving–Cooling Modified Purple Yam (Dioscorea alata L.) Starch for the Development of Edible Films

Abstract This study aimed to analyze the effect of purple yam (Dioscorea alata L.) starch modification through repeated autoclaving–cooling cycles and different starch concentrations on the characteristics of edible films, as well as to determine the best treatment combination. A factorial Completely Randomized Design (CRD) was applied with two factors, namely starch modification (native, one cycle, and two cycles) and starch concentration (5%, 6%, and 7%), with three replications, resulting in 27 experimental units. The results showed that starch yield significantly increased from 20.42% (native) to 90.13% (one cycle) and 98.16% (two cycles). Starch pH increased from 5.80 to 6.81–6.89, moisture content decreased from 8.72% to 7.26%, and crude fiber rose from 5.22% to 6.56%. SEM analysis revealed progressive granule disruption, producing edible films with denser, more homogeneous, and crack-free structures. Starch color parameters indicated decreased lightness (L*) from 67.49 to 65.59, increased a* from 5.95 to 6.39, and increased b* from 13.20 to 14.35. In contrast, edible film color varied with L* values of 71.96–77.47, a* 3.56–5.17, and b* 14.78–18.91, influenced by the interaction between starch concentration and modification cycles. Anthocyanin content increased both in starch (from 3.17 to 5.82–5.86 mg/g) and edible films (from 8.07 to 11.10–11.12 mg/g). Functional properties of the edible films showed stable thickness (0.20–0.24 mm), variable transparency and solubility, reduced water vapor transmission rate (WVTR) down to 3.69 g/m²·day, and improved tensile strength up to 292.33 g. In addition, crude fiber content in edible films increased up to 4.70%, with relatively stable pH ranging from 5.72 to 6.17. The novelty of this study lies in the application of repeated autoclaving–cooling on purple yam starch, which not only enhanced the technological properties of edible films (thickness, transparency, mechanical strength, and barrier performance) but also increased anthocyanin content, resulting in dual-function edible films as eco-friendly biodegradable packaging and a natural antioxidant source.