Light stable carboxymethyl cellulose-based smart packaging film for real-time visual detecting the freshness of food

The light-induced degradation of anthocyanin (Anth) for long time caused the color loss and poor color response when Anth was employed as the pH indicator within intelligent packaging. Herein, aiming to design smart packaging film with enhanced light stability, a sort of sodium carboxymethyl cellulose (CMC)/Anth/enzymatic lignin (CMC/Anth/EL) was proposed, in which enzymatic lignin served as the armor to protect Anth by absorbing the light. When exposed to natural illumination for 7 days, the Anth loss rate was reduced from 32.44% for pristine CMC/Anth to 3.82% for the optimized CMC/Anth/EL 3 . Moreover, the total color difference (ΔE) of CMC/Anth was reduced from 30.41 to 14.09 with the reduction of 53.67% to volatile ammonia, whereas the ΔE reduction was merely 4.34% for CMC/Anth/EL 3 . In practical application for monitoring the freshness of shrimp, the biodegradable CMC/Anth/EL 3 film presented visually discernible color response toward volatile bioamine, which was highly correlated with the freshness index, such as total volatile basic nitrogen (TVB-N, 7.26-26.67 mg/g) and pH (6.84-7.69). Our findings not only provided a new pathway to high-value utilize the waste residue, but also boosted the development of intelligent packaging with reinforced light stability.