Green extraction of cellulose fibers from pineapple crown waste for the development of pH-sensitive bioplastic films based on starch and purple cabbage anthocyanins

Abstract

Environmental concerns over plastic waste and food safety have driven the development of smart and biodegradable active packaging materials. This study reports an intelligent bioplastic film capable of real-time monitoring of food freshness. Cellulose fibers (CFs) were extracted from pineapple crown waste through alkali and hydrogen peroxide treatment, followed by citric acid hydrolysis to enhance crystallinity. The extraction yield of cellulose fibers was 48.25 ± 0.37%, with a crystallinity index of 78.54%, confirming the effective removal of amorphous components. The obtained cellulose fibers were incorporated as reinforcing agents into cassava starch films containing a fixed amount of purple cabbage anthocyanin extract (2 mL, 255.49 mg L⁻¹). Mechanical analysis revealed that the optimal cellulose concentration was 16 wt%. The resulting intelligent bioplastic film exhibited an apparent color change from red to green or yellow, consistent with the behavior of an anthocyanin solution. During shrimp storage, the film functioned as a freshness indicator, changing color from purple to blue upon exposure to volatile amines such as trimethylamine (TMA), dimethylamine (DMA), and ammonia (NH₃). These findings demonstrate the potential of this intelligent biodegradable packaging for real-time food quality monitoring and environmental sustainability.