Abstract
Biodegradable, intelligent pH-responsive films were prepared by casting using konjac glucomannan (KGM), roselle anthocyanin (RA), and TEMPO-oxidized cellulose nanofibrils (TOCNF). The effects of TOCNF content (0-0.2 wt%) on the nano-microstructure, mechanical properties, barrier performance, and pH-indicator properties were investigated. SEM, AFM, and SAXS analyses showed that KR/T-c (with 0.15 wt% TOCNF) formed a dense and uniform nano-network with the highest fractal dimension (n = 1.50) and moderate correlation length (ξ = 6.17 nm). This optimized nano-microstructure conferred KR/T-c with the highest tensile strength (151.75 MPa), the largest water contact angle (110°), and excellent water vapor and oxygen barrier properties. The films exhibited distinct pH-sensitive color changes from red (pH 3-4) to yellow-brown (pH 10), with color primarily governed by RA. During Agaricus bisporus storage, both KR and KR/T-c films exhibited real-time color changes, while KR/T-c showed superior preservation effects. The KR/T-c film shows considerable potential for real-time freshness monitoring in intelligent food packaging.