Impact of Grinding Under Different Vacuum Levels on Browning, Antioxidant Activity, and Phenolic Compounds of Asian Pears (<i>Pyrus pyrifolia</i> Niitaka)

Abstract

The grinding process of fruits generally causes rapid browning and loss of antioxidant activity, as it increases the particle surface area by reducing the size, thereby increasing the exposure of phenolic compounds to oxygen. In this study, the impact of various vacuum levels (3 kPa, 7 kPa, 13 kPa, 20 kPa, and 101 kPa) during grinding on the quality characteristics of Asian pears such as their color, antioxidant activity, and phenolic content was investigated. The results revealed that grinding of pears according to the degree of vacuum showed significant differences in the color change and loss of antioxidant activity of the pears and exhibited a logarithmic scale effect rather than an arithmetic one. In particular, browning was suppressed, and antioxidant activity was well maintained when the grinding was carried out at 3 kPa. Notably, among the five key phenolic compounds identified, catechin, procyanidin B2, and quercetin were well maintained in the pears ground under high vacuum. These findings emphasize the potential value of vacuum grinding for maximizing the nutritional content of pear by reducing the rate of oxidation and browning.