Effects of Ultra-high Pressure Treatment on Quality and Its Shelf Life of Freshly Squeezed Compound Juice

In order to make the active ingredients and flavor substances of fruit juice after sterilization treatment closer to the original freshly squeezed fruit juice, the compound juice was prepared with kiwifruit, pineapple and mango as raw materials in this paper. The effects of ultra-high pressure and heat treatment (85 ℃, 5 min) on the quality and shelf life of freshly squeezed compound juice were compared. The results showed that, as the volume ratio of the mixed juice was V_{pineapple pulp}:V_{kiwi pulp}:V_{mango pulp}=4:2:4, the pH, b^* value and soluble solid content of the juice treated at 450 MPa, 25 ℃ and 15 min of ultra-high pressure had no significant difference (P>0.05) with the traditional heat treatment, but the loss of vitamin C content and polyphenol content decreased by 12.1% and 17.5%, respectively. By analyzing the main volatile components of the compound juice, it was found that the loss of flavor substances such as enes, esters, alcohols, ketones, and aldehydes in the UHP treatment juice was significantly less than that in the heat treatment juice (P<0.05). The content of furfural was 0, the relative contents of acetone and 1-octene-3-one were reduced by 68.4% and 41.4%, respectively. The total number of colonies, the bactericidal effect of mold and yeast were all in line with the current hygienic standards of beverages. Through the Q₁₀ model to forecast the shelf life, the shelf life of the juice could be up to 103 days stored at 4 ℃. In conclusion, the ultra-high pressure treatment of freshly squeezed compound juice could effectively kill microorganisms and maintain the natural quality of compound juice, and endow juice a longer shelf life.