Abstract: This paper explored the effect of ultra-high pressure (UHP) treatment at different pressures and durations on the quality of persimmon pulp. The results showed that the total number of bacteria in the pulp decreased with increasing pressure and time and treatment at 400 MPa for 15 min could meet the requirement of commercial sterility. After treatment, the color and the contents of soluble sugar, soluble solid and titratable acids were not changed significantly (P > 0.05) when compared with the control group. However, vitamin C content gradually declined with the increase in pressure and time, with the maximum loss of 8.06% being observed at 600 MPa and 20 min. Peroxidase (POD) activity also declined with increasing pressure and time, and polyphenol oxidase (PPO) activity similarly showed a gradual decrease with increasing treatment time; however it initially rose and then fell with increasing pressure. Polyphenol content also showed an initial increase followed by a decrease with pressure, but it showed a general increasing trend with treatment time, with the maximum value being attained at 400 MPa and 20 min. The antioxidant capacity was much higher when compared with the control group, but no significant differences were observed among the treatment groups (P > 0.05). Compared with the control samples, soluble tannin content was increased after UHP treatment to a level below the critical value for astringency (2 mg/g). In conclusion, UHP treatment has only a slight effect on the sensory quality and can maintain the nutritional quality to a large extent and improve the antioxidant activity of persimmon pulp. Moreover, this treatment can lead to elimination of astringency.

Key words: persimmon pulp, ultra-high pressure, quality, antioxidant activity