Triple-action packaging: Food protection and monitoring enabled by agri-food side streams

Food safety denotes a major concern for the society, industries, and policymakers. Among the incipient strategies to recognize products that are unfit for consumption is smart packaging that can respond to changes in composition or storage conditions throughout spoilage and communicate this to consumers. Herein, we report on a halochromic packaging that switches colors in response to changes in pH and ammonia concentration upon fish decay. Different lignin and grape seed and peel extract contents are shown to play a role on the physicochemical, morphological, mechanical, and biological features of the packaging, which are then easily tailored by simply varrying composition. Lignin was shown to improve the water barrier properties (water vapor permeability of 0.19 ± 0.01 g mm kPa−1 h−1 m−2 and water contact angle of 89 ± 3°) of chitosan-based films, but hindered its swelling (over three times) and mechanical resistance with decreased elongation at break and Young's modulus, which was tuned by the extracts. The antioxidant activity was increased to 47% by adding only 0.50 wt% of grape seed extract, and its antimicrobial activity against Staphylococcus aureus surpassed that of extract-free samples. The capacity for real-time detecting NH3 vapor was validated for naked eye, as per an evident color change from yellow to orange. Finally, a film comprising chitosan/lignin/grape seed extract was successfully applied as a sticker indicator to monitor the spoilage of fish over time. Importantly, besides ensuring and tracking food freshness in a real-time fashion, this study is set out to mitigate food waste generation, approach that is boosted when we valorize agri-food residual streams to fabricate triple-action materials. Overall, our waste-only materials integrate the three roles (i.e., antimicrobial, antioxidant, and intelligent) to prevent further waste, plus burdens related to food spoilage.