Developing a smart colorimetric indicator film by incorporating pomegranate peel powder into cassava starch film

The purpose of this study was to investigate the effect of pomegranate peel powder on the physicochemical, barrier, and pH sensitivity of the films based on cassava starch. The pomegranate peel powder (PPP) was used at levels of 2, 4, 6, and 8% w/v in starch film formulation, and the thickness, water solubility, water vapor (WVP) and oxygen permeability, and opacity were determined, and the color variations of the films were also measured after immersion in different pH buffers (pH 4.0-9.0). The results demonstrated the addition of PPP to film formulation and increasing its levels, the water solubility, opacity, WVP, and oxygen permeability were increased (p<0.05), so that the values of these parameters in the control sample were 33.78%, 0.65 mm-1, 6.92 × 10-10 g/s.m.Pa, and 4.06 cc-mil/m2.Day, respectively, and in the film containing 8% of PPP reached 41.32%, 1.25 mm-1, 7.72 × 10-10 g/s.m.Pa, and 5.63 cc-mil/m2.Day, respectively. The results of examining the sensitivity of films to pH showed that the color of the produced films changed against changes in solution pH so that with increasing the pH of the solution to the neutral and alkaline range, the color of the films changed from reddish pink to green. According to obtained results, it can be concluded that the intelligent films based on cassava starch containing PPP can be used as pH-sensitive indicators to display the freshness of food products.