Intelligent pH-sensitive films from whole arrowroot powder and soy protein isolate incorporating red cabbage anthocyanin: monitoring freshness of shrimps and ammonia in fish farming ponds

The pH-sensitive intelligent film is a much-awaited development in the field of packaging as it informs the consumers about the quality of the prepacked food by its visually detectable color changes. In this study, the indicator films (AP-SPI-RCE) were produced using whole arrowroot powder (AP), soy protein isolate (SPI), and food-grade red cabbage anthocyanin (RCE). Two different concentrations of RCE (5% and 7% (based on AP)) were added to AP-SPI matrices to form AP-SPI-RCE₅ and AP-SPI-RCE₇ films. The AP-SPI-RCE₅ film showed the highest tensile strength, thermal stability, 16% decrease in moisture content, and 41% decrease in solubility. Films incorporated with anthocyanin showed distinguishable color changes in different pH buffers and good sensitivity for ammonia vapor detection. The indicator film displayed visual color changes corresponding to pH and total volatile basic nitrogen (TVB-N) changes when the shrimp sample was spoiled. Hence, this food-grade anthocyanin incorporated film can act as a smart material to detect spoilage of fresh shrimp and meat which produce ammonia on spoilage. In addition, these strips are suggested to be utilized in the monitoring of the ammonia concentration in fish farming ponds.