Novel pH-sensitive films based on starch/polyvinyl alcohol and food anthocyanins as a visual indicator of shrimp deterioration

Intelligent packaging can provide better preservation and advanced convenience for consumers. In this study, corn starch and polyvinyl alcohol (PVA) were used to produce films. Two easily accessible anthocyanin sources-purple sweet potato extracts (PSPE) and red cabbage extracts (RCE), were added respectively to evaluate their potential of indicating food freshness. Film incorporated with PSPE or RCE showed distinguishable color changes in different buffers. Water vapor permeability (WVP) was not significantly (p > 0.05) affected by addition of RCE or lower level PSPE. As the extract content increased, a significant (p < 0.05) increase in thickness (from 64.0 to 97.7 or 85.5 μm with addition of PSPE or RCE, respectively), mechanical (from 7.3 to 11.3 or 9.1 MPa in TS, and from 92% to 249% or 284% in EB, added with PSPE or RCE, respectively), and thermal properties was observed, with the light transmittance reduced profoundly. PS-PSPE film exhibited bolder color, better mechanical properties and lower light transmittance than PS-RCE film at lower extract content. In addition, application for indicating shrimp freshness was conducted. The developed film presented visual color changes corresponding to TVB-N variation when shrimps were spoiled, showing its great potential as an indicator for monitoring shrimp freshness.