Smart pH-sensitive films based on biomaterials: Preparation from soy protein with hybrid fillers of CuO nanorods, cellulose nanofibrils, and Clitoria ternatea anthocyanin

Background: The environmental concern about plastic consumption always rises the need for alternate materials. Plastics being widely employed in the food packaging and hence highly demands such alternatives. The toxicity and pollution produced by the conventional petroleum-based plastics can be reduced by the usage of bioplastics. The area of food packaging using various biopolymer composites has grown much and is developing new materials by incorporating various nanofillers, especially based on green synthesis approach. This study focuses on the usage of soy protein isolate as a matrix for such films and uses copper nanomaterials and cellulose as reinforcing agent. Results: An active and intelligent bio nanocomposite thin film based on soy protein isolate (SPI) was prepared. Copper oxide nanorods(CuONRs) were synthesised from ascorbic acid and honey, cellulose nanofibrils (CNF) were extracted from the Acasiacaesia using steam explosion technique and anthocyanin was extracted from Clitoria ternatea flower (CTE). The effect of the addition of CuONR (5%, 10%), CNF (10%), and CTE (7%) on the physiomechanical, barrier, antibacterial, and antioxidant properties of the films was investigated. SEM showed uniform distribution of CuONR/CNF/CTE in the SPI matrix. Conclusion: The addition of CuO and CNF was found to effectively increase the mechanical property, thermal stability, and decrease the moisture content percentage of the films. In contrast, the addition of CTE made the film pH-sensitive. SPI-CuONR/CNF/CTE films showed good antioxidants and antibacterial properties. Fabricated film could act both as a pH sensor for detecting the evolution of acidic and basic gases and as active packaging material to extend the shelf life of food materials.