A Visual pH Indicator through Purple Cabbage Dye for Freshness Test of Venison

Abstract

: A visual pH indicator through purple cabbage dye is selected to test the freshness of venison. Chitosan and cassava starch of an equal weight were used to prepare the film-forming matrix of the indicator. The crystallization of natural purple cabbage dyes with a weight ratio of 5%, 10%, 20% and 40% were added to the matrix, respectively. The pH color test showed that the natural purple cabbage lyophilized powder with a weight ratio of 40% was the best for the pH indicator, which was used to test the freshness of venison stored at 4℃. Th e total bacterial count, volatile basic nitrogen (TVB-N) and thiobarbituric acid (TBA) of venison were tested through an experiment. When stored at under 4℃, a significant color change of the indicator from pink to blue-green was shown when the total amount of volatile basic nitrogen (TVB-N) (22.78 mg/100 g) exceeded the critical value (20 mg/100 g). The test result showed that the indicator was very sensitive to pH value and it would help customers identify the freshness of venison.