Multifunctional performance of chitosan/soy protein isolation-based films impregnated carbon dots/anthocyanin derived from purple hull pistachio for tracking and extending the shelf life of fish

Abstract

The present study aimed to develop a sustainable biopolymer film that exhibits active and intelligent properties. The chitosan/soy protein isolation (Cs/SPI) based film was prepared by blending purple hull pistachio anthocyanin (PHPA) with carbon dots (CDs), which were synthesized using a by-product from purple hull pistachio (PHP) extraction. PHPA and CDs were shown to be compatible with the Cs/SPI biopolymer films. The resulting matrix was a homogeneous film with improved physico-mechanical properties. The biopolymer films were characterized by their various desirable properties, including 100% UV protection, potent antibacterial activity against S.aureus and E. coli strains with inhibition zonoe about 22.1 ± 36±0.24 mm and 20.36 ± 0.21 mm, respectively, and strong antioxidant properties (DPPH; 82.3 ± 0.1 % and ABTS; 90.6 ± 0.1 %). The film was also found to exhibit distinguishable colorimetric responses to pH 2–12 buffers and volatile ammonia. The packaging test of CS/SPI/PHPA/PHP-CDs film in scenario one (intelligent assay) for evaluation through fish freshness monitoring showed that the film's color changed from light pink (fresh fish) to yellow/brownish (spoilage fish) during storage at 4 °C and 25 °C. Also, scenario two (active assay) at 4 °C showed the ability to increase the shelf life of fish up to 12 days. The study demonstrated that the biopolymer films have exhibited exceptional adaptability, making it a highly promising option for prompt and effective on-site detection of food quality. Furthermore, the film's capacity to prolong the shelf life of fish and reduce the rate of quality degradation during storage positions it as an outstanding contender for multifunctional film applications in the food industry.