Construction of sustainable food packaging indicator films based on rice bran carboxylated cellulose nanocrystals

Sustainable carboxylated rice bran cellulose nanocrystals (CCNC) were synthesized via citric acid hydrolysis. • KGM-CCNC films exhibit significantly improved mechanical strength, water solubility and water- and oxygen-barrier properties. • Anthocyanin-KGM-CCNC composite film serves as a freshness indicator for the real-time monitoring of pork freshness. Food packaging indicator films are key active-intelligent materials for food preservation and quality monitoring. Natural polysaccharides like konjac glucomannan (KGM) have good film-forming and biodegradable properties but suffer from poor mechanical strength, limiting their food packaging applications. Herein, rice bran carboxylated cellulose nanocrystals (CCNC) were prepared via green citric acid hydrolysis and characterized for chemical structure, crystallinity and thermal stability. CCNC-KGM composite films were then fabricated, with morphology, mechanical properties, water vapor/oxygen barrier performance and surface wettability tested systematically. The film with 1% CCNC showed optimal mechanical properties and minimal water solubility. By incorporating pH-responsive anthocyanins, the composite film achieved visual pork freshness monitoring via color changes. At 4°C, the indicator film containing 0.25 grams of anthocyanin has the best preservation effect on pork. This study developed high-performance intelligent packaging films using rice bran cellulose, laying a critical foundation for advancing natural polysaccharide-based smart packaging materials. Rice bran was sequentially defatted to remove lipids and alkaline-treated to eliminate proteins, followed by further alkaline treatment and bleaching to extract purified cellulose through removal of lignin and hemicellulose. The amorphous regions of this purified cellulose were then selectively degraded via citric acid hydrolysis, producing needle-like carboxylated cellulose nanocrystals (CCNC). The CCNC was subsequently incorporated as a reinforcing phase into a konjac glucomannan (KGM) matrix, with the resulting composite being fabricated into food packaging films using solution-casting methodology. Download: Download high-res image (137KB) Download: Download full-size image