Fabricating κ-carrageenan/carboxymethyl cellulose films encapsulating bromothymol blue fixed rice straw fiber for monitoring meat freshness

Intelligent films monitoring food quality are potential to use in people's life. The safety and sensitivity are of great importance. In this study, a dual synergistic design was developed to construct a safely and sensitively smart film in which quaternary ammonium groups modified rice straw fiber (CRSF) attached bromothymol blue (BTB) was embedded into an anion kappa-carrageenan/carboxymethyl cellulose (CMC) matrix. SEM results revealed the good interfacial compatibility between the matrix and the modified fiber. Substitution degree (DS) of quaternary ammonium groups and addition amount of CRSF-BTBs interestingly affected the properties of the film. That containing 1% CRSF-BTB with DS of 19.3% exhibited distinguishable colorimetric response in only 3.0 s at humidity of 75.0% with 0.8 mL of ammonia, and lower BTB release rate of 2.87% in 95% ethanol solution. The film displayed visible color changes from yellow to dark-blue as meat freshness decreased. This study provides a novel strategy to develop a highly smart film for insuring the food safety.