Intelligent double-layer polymers based on carboxymethyl cellulose-cellulose nanocrystals film and poly(lactic acid)-Viola odorata petal anthocyanins nanofibers to monitor food freshness.

The present study was conducted with the aim of fabricating smart bilayer polymers based on carboxymethyl cellulose-cellulose nanocrystals film and poly(lactic acid)- Viola odorata extract nanofibers (CMC-CNC and PLA-VOE) for freshness monitoring of Pacific white shrimps, minced lamb meat, chicken fillets, and rainbow trout fillets, during refrigerated storage conditions. The fabricated indicators based on CMC-PLA-VOE 5%, CMC-CNC 1%-PLA-VOE 5%, and CMC-CNC 3%-PLA-VOE 5% presented remarkable color changes in pH 1–12 buffer solutions, including red at pH 1–6, violet at pH 7–8, green at pH 9–10, and brown at pH 11–12. Significantly lower water vapor permeability and oxygen transmission rate of prepared polymers were found in comparison with the control groups (P < 0.05). Regarding the monitoring of food samples in real-time, the samples spoiled after 3 days, evidenced by total viable count, psychrotrophic bacterial count, total volatile basic nitrogen, and pH values of 7.17–7.54 log CFU/g, 5.68–6.23 log CFU/g, 25.14–28.12 mg N/100 g, and 7.10–7.66, respectively. Meanwhile, the noticeable color change of prepared indicators from white to violet (day 3) and finally dark violet (day 7) was observed, indicating a potential application in intelligent packaging for real-time control of the freshness of perishable food samples. • Poly(lactic acid)- Viola odorata anthocyanins nanofibers had excellent sensitivity to pH 1–12 and NH 3. • The color indicators changed from white to dark violet during food spoilage. • The indicators identified spoilage in the refrigerated shrimps, minced lamb meat, chicken fillets, and rainbow trout fillets. • V. odorata anthocyanins had antimicrobial and antioxidant activities. • The water and oxygen permeability properties of polymers reduced using V. odorata extract and cellulose nanocrystals. [ABSTRACT FROM AUTHOR]