Extraction and Identification of Anthocyanins from Pitaya Peel and Their Application in Meat Freshness Indicator Film

Abstract:

In order to improve the comprehensive utilization rate of pitaya peel and enhance consumers’ confidence in food safety, fresh pitaya peel was used as the raw material in the experiments for extracting and characterizing the anthocyanin components of the pitaya peel. The anthocyanin extracts were used to prepare a meat freshness indicator film, and its pH and temperature stability, as well as its final application to pork freshness monitoring, were examined. The results showed that the optimal process for extracting anthocyanins from pitaya peel was: 50% ethanol by volume fraction, materialliquid ratio (mass of pitaya peel: volume of ethanol) as 1:39 g/mL, ultrasonication time as 19 min, and pectinase addition as 1.6 wt.%. Under these conditions, the content of anthocyanins was 218.25 mg/100 g. Seven anthocyanins were identified in the anthocyanin extract from pitaya peel, among which the relative content of petunidin and its derivatives was up to 89.76%; the color of anthocyanin extract was more stable under the conditions of 5~25 ℃ and pH 4~5; the total volatile basic nitrogen (TVB-N) of pork reached the spoilage threshold (15 mg/100 g) at the 12th h of storage (25 ℃). The meat freshness indicator film changed from purplish red to light yellow, with the color difference ΔE of the freshness indicator film being 5.38 (>5, which could be easily recognized by human eyes). The Pearson's r between TVB-N and ΔE was 0.961 2 (P<0.01), indicating that there was a strong correlation between the two, and that the indicator film was able to indicate the freshness of meat. This study provides a scientific basis for the high-value utilization of pitaya by-products.