NaCl treatment with low density polyethylene packaging bags can enhance the aroma of fresh-cut apple, not only inhibit its browning

Abstract

NaCl is regarded as a low cost and effective anti-browning agent for fresh-cut apples, but is rarely discussed on keeping flavor. In this study, the anti-browning effect of 0.1 mol/L NaCl with low density polyethylene (LDPE) packaging bags for apple was verified by lower browning degree, the total phenolic content, polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) activity and relative genes expression. The browning score and flavor evaluation of fresh-cut apples with NaCl treatment was 1.49 and 1.47 times that of the control on the 12th d, which showed NaCl treatment increased the business value of fresh-cut apples. Butanoic acid methyl ester, butanoic acid 2-methyl-, methyl ester and hexenoic acid methyl ester were markedly higher in NaCl treatment slices than the control. Additionally, the linolenic acid content increased with NaCl treatment, which was 2.3 times that of the control on the 12th day. Enzymes activity and relative genes expression in lipoxygenase (LOX) pathway including LOX, ethanol dehydrogenase (ADH), and alcohol-acyltransferase (AAT) was activated in apple slices with NaCl treatment. Among them, AAT1 expression changed the most, eight times that of the control on day 1. However, the activity and relative expression of pyruvate decarboxylase (PDC) related to ethanol synthesis was inhibited. Moreover, NaCl enhanced β‑glucosidase (BGL) activity of fresh-cut apples by 1.9 times on day 1 and its concentration in the reaction system was proportional to the BGL activity. The results indicate NaCl treatment with LDPE packaging is an effective method to maintain appearance and regulating flavor qualities of fresh-cut apples.