Novel colorimetric films based on polyvinyl alcohol/sodium carboxymethyl cellulose doped with anthocyanins and betacyanins to monitor pork freshness

A novel colorimetric film was developed from polyvinyl alcohol/sodium carboxymethyl cellulose (PVA/CMC-Na, CPA) incorporated with anthocyanins (AHO) or betacyanins (BTA) or AHO and BTA mixtures (in the mass ratios of 2:2, 3:1, 1:3) for intelligent packaging. Fourier transform infrared (FTIR) and scanning electron microscope (SEM) illustrated that AHO/BTA were immobilized into CPA network and improved compatibility of PVA and CMC-Na. The incorporation of AHO/BTA increased the tensile strength (TS), elongation at break (EAB), thickness and water solubility (WS) of the sample but decreased the crystallinity and swelling index (SI) of the sample. Furthermore, the colorimetric films presented antioxidant activity besides antibacterial activity against Escherichia coli and Staphylococcus aureus. The colorimetric film incorporated with AHO and BTA at a mass ratio of 3:1 indicated different colors to represent the freshness of pork. The novel colorimetric film possesses great potential in intelligent packaging for monitoring the real-time freshness of pork products.