Study of polyvinyl alcohol/starch-based hydrogel pads loaded with blueberry anthocyanin/citric acid/gardenia red/yellow/blue overlapping color system for monitoring beef freshness.

Abstract

In this study, a water-absorbent indicator pad with blueberry anthocyanins (BA), citric acid (CA), gardenia yellow (Y), gardenia red (R), gardenia blue (B) and their compound colors superimposed in a polyvinyl alcohol/starch-based hydrogel was prepared for dynamic monitoring of beef freshness at 4 °C. The addition of CA increased the redness of the pads compared to only BA, whereas the gardenia yellow/gardenia blue mixture significantly increased the range of color change of the indicator pads at pH 6-7 (brownish-red to light khaki to grassy-green) compared to the other colors. The initial color of the indicator pads was red, which gradually turned green with the volatilization of nitrogenous compounds from the beef and the leaching of the gravy. Combined with the correlation analysis between the color change of the indicator pads and the beef storage process, it was verified that the indicator pads could reflect the freshness of beef simply and accurately.