Effect of Ultra-high Pressure Treatment on the Quality of Persimmon Pulp

Different pressures and different durations of ultra-high pressure treatment were conducted for persimmon pulp after vacuum packing. The results showed that with the increase of pressure and extension of duration, the total number of bacteria in persimmon pulp decreased gradually. The 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 solids and titratable acid of persimmon pulp were not changed significantly compared with the control group (P>0.05). The content of vitamin C in persimmon pulp declined gradually with the increase in pressure and time, with the maximum loss of 8.06% observed at 600 MPa for 20 min. Peroxidase (POD) activity also declined gradually with the increase of pressure and time. The activity of polyphenol oxidase (PPO) declined gradually with the increase of time, and increased first and then decreased with the increase of pressure. The content of polyphenols increased first and then decreased with the increase in pressure, and tended to increase overall with the increase in time. Under the treatment of 400 MPa for 20 min, the content of polyphenols reached the maximum. The antioxidant capacity of persimmon pulp after ultra-high pressure treatment was higher than that in the control group, but no significant differences were found among the treatment groups (P>0.05). Compared with the control group, soluble tannin content was increased after ultra-high pressure treatment, but was far below the critical value for astringency (2 mg/g). In conclusion, ultra-high pressure treatment has only a slight effect on the sensory quality of persimmon pulp and can maintain its nutritional quality to a large extent and improve its antioxidant capacity. Moreover, ultra-high pressure treatment can eliminate astringency completely.