Biomimetic supramolecular peptide nanozymes-mediated dual-readout hydrogel label for headspace monitoring of meat spoilage

Abstract

To address the limitation that fixed date labels in food packaging and shelf-life management fail to accurately reflect actual spoilage progression, this study developed a β-alanine-L-histidine–hemin (AH-He) self-assembled peroxidase-mimic for detecting volatile alkaline spoilage markers, using ammonia as a representative model analyte. The AH-He nanozyme-based sensing system delivered a rapid and sensitive colorimetric response based on the 3, 3′, 5, 5′-tetramethylbenzidine (TMB)/hydrogen peroxide (H₂O₂) reaction, achieving a detection limit of 0.057 mM with a response time below 100 s, and it maintained remarkable catalytic stability under elevated temperatures and prolonged storage conditions. Building on this, the AH-He nanozyme was co-encapsulated with pH-sensitive fluorophore in an agarose hydrogel, yielding a dual-mode freshness label for non-contact headspace monitoring in packaging. As the analyte concentration increases, blue coloration of the AH-He nanozyme gradually faded while green fluorescence of the fluorophore intensified, enabling reverse dual-channel self-calibration to reduce misjudgment. When applied to headspace monitoring of meat spoilage at 25 °C, 4 °C, and −20 °C, the image-quantified signals (G/B) showed strong correlations with the total volatile basic nitrogen (TVB-N) benchmark values, with correlation coefficients of 0.991 and 0.985 for the colorimetric and fluorescence channels, respectively. These results provide proof-of-concept evidence for a packaging-integrable dual-readout freshness indicator capable of non-contact monitoring of volatile alkaline spoilage markers in meat packaging.