Abstract: 【Objective】 The optimum conditions of ultra-high pressure (UHP) sterilization for kiwi fruit pulp and the effects of sterilization during storage period after ultrahigh pressure treatment were investigated by using Hayward Kiwifruit as raw materials. This study will provide an experimental reference for the non-thermal processing of kiwi fruit and its products development. 【Method】 The kiwi fruit pulp was obtained by cold crushing technology, the response surface method (RSM) was used to establish the mathematical model of ultra-high pressure sterilization conditions for kiwi fruit pulp to obtain the optimum conditions, and the total number of colonies, Vitamin C and browning degree were used as the evaluation indexes. The changes of the total number of colonies, mold and yeast and Escherichia coli group of kiwi fruit pulp were studied with microbiological analysis methods during the storage period at temperatures of 4℃ and -20℃ after ultrahigh pressure treatment. 【Result】 The optimum sterilization conditions of UHP treatment on kiwi fruit pulp were pressure 497 MPa, temperature 27℃, holding time 24 min through the single factor test and the response surface analysis of Box-Behnken model. Under this optimal sterilization condition, the total lethality rates of total number of colonies, Escherichia coli group and mold and yeast were 73.18%, 97.46% and 100.00%, respectively, in kiwi fruit pulp after UHP treatment. Under the standard range, the increments of total number of colonies in kiwi fruit pulp was bigger, which increased significantly of 97.19% and 85.98% respectively after storage for 6 and 14 weeks at 4℃, -20℃, compared with the first day of storage, but the growth rate of total number of colonies was small. While the increments rates of Escherichia coli group, mold and yeast in kiwi fruit pulp after UHP treatment were relatively small, the content of Escherichia coli group, mold and yeast only was 1.36, 0.67 and 0.32, 0.35 lg (CFU/mL) after stored 6 and 14 weeks at 4℃, -20℃, respectively. 【Conclusion】 As a new type of non-thermal sterilization method, ultra-high pressure technology had good sterilization effects for the heat sensitivity materials of kiwi fruit pulp. The kiwi fruit pulp which was used as processing materials and sterilized by the ultra-high pressure technology could be stored 14 weeks at -20℃ still to meet the commercial aseptic requirements, so the ultra-high pressure sterilization combined with the low temperature storage will benefit the further storage, process and utilization of kiwi fruit pulp produced by cold crushing.

Key words: kiwi fruit, pulp, ultrahigh pressure sterilization, response surface method, storage