Development and characterization of cassava starch films incorporated with purple yam (Dioscorea alata L.) peel anthocyanins

Abstract

The packaging industry is now geared towards natural and biodegradable raw materials to reduce packaging wastes. In this study, purple yam (Dioscorea alata L.) peels were utilized to extract anthocyanins to be incorporated as a pH indicator in cassava starch films. The extract was analyzed for its total monomeric anthocyanin content (TMAC) using the pH differential method, and antioxidant activity using the DPPH assay. Results showed that the extract contains 155 mg/L cyanidin-3-glucoside and high antioxidant activity of 78.84%. Using the casting technique, thin films were made from cassava starch and glycerol, with varying amounts of the extract (0, 10, 20, 30 and 50%). The films were characterized by their color properties, water activity (Aw) and tensile strength (TS). Results showed decreasing values of L* , a* , b* as the concentration of the extract increased. No significant difference (p>0.05) was observed in the Aw and TS of the control film and the colored films. There was no trend observed in the Aw and TS of the films. The film with 30% extract recorded the lowest Aw (0.214) while the film with 40% extract recorded the highest tensile strength (0.706). The film with the highest TS was subjected to color response analysis by immersing the films in buffer solutions at different pH levels (pH 1.0-12.0) for 10 mins, and the time when the first color change was observed was recorded. The fastest responses were observed at the extreme pH levels (pH 1.0–2.0; 10.0–12.0). This study was able to conclude that purple yam peel extract has the potential as a pH indicator in cassava starch films for application as intelligent packaging.