Effect of vacuum - grinding on the stability of anthocyanins, ascorbic acid, and oxidative enzyme activity of strawberry

Abstract

In this study, strawberries were ground at vacuum levels of 2.67, 6.67, 13.33, 19.99, and 101.33 kPa (atmospheric pressure) using a specially designed vacuum grinding and continuous packaging device. The grinding at higher vacuum levels led to better maintenance of ascorbic acid and anthocyanins, resulting in a higher antioxidant activity and redness due to the low oxygen availability limiting oxidation. Vacuum-grinding below 2.67 kPa prevented the oxidation of pelargonidin glycosides to a greater degree than that of cyanidin and delphinidin glycoside, due to structural differences related to the number of hydroxyl groups in the B ring, revealing the faster oxidation rate of diphenolic anthocyanins. The model fits indicated a logarithmic rather than a linear degradation as the oxygen level increased, indicating that even small amount of oxygen may cause drastic quality deterioration during grinding. Overall, our results indicate that vacuum grinding at very low oxygen levels is an effective technology to prevent the oxidation of anthocyanins and ascorbic acid, resulting in higher redness and antioxidant activities in strawberries.