Development of pH-sensitive films based on buckwheat starch, critic acid and rose petal extract for active food packaging

Abstract

The pH sensitive films were developed by casting method using buckwheat starch (BS, 5% dry basis) as a base material, citric acid (CA, 1–5% w/w of dry starch) as a crosslinker, and natural rose petals extract (RE, 5–15% v/v of the total solution) as a pH indicator. RE increased the thickness, moisture, elongation at break, UV–vis light barrier ability, and antioxidant properties of films. The interaction between anthocyanin and starch was confirmed by FTIR, which showed band shifting near 995 cm−1. At higher RE concentrations, the surface of the film became rough and uneven due to agglomeration of extract materials. In contrast, CA improved water solubility, tensile strength, and UV rays blocking by forming ester linkage between starch molecules. Increasing RE and CA reduced the crystallinity of films (from 37.32% to 18.56%), which improved flexibility. All RE-containing films changed their color from pinkish to greenish yellow as the pH increased from 5 to 9. The film containing 5% of CA and 6.36% of RE was found to be more desirable and could be used as smart packaging for monitoring food quality and safety.