Quality Changes of Kiwifruit NFC Juice during Storage with UHP and HTST Sterilization Treatment

In order to provide a theoretical basis for determining the shelf life of not-from-concentrate(NFC)juice products in in China,the quality changes of NFC kiwifruit juice with different sterilization treatment(Ultra-high pressure,UHP and High temperature short-time,HTST)during storage periods of 4 weeks at 4 ℃ were compared. The NFC juice was prepared using Hayward kiwifruit as raw materials and treated with UHP(400 MPa,15 min)and HTST(95 ℃,30 s),the changes of physicochemical and nutritive indexes,microbial populations,antioxidant activities and aroma components of NFC kiwifruit juice were studied during storage using chemistry,microbiology and other methods,as well as instrumental analysis methods of GC-MS. The results showed that the content of V_C and total sugar in NFC kiwifruit juice treated by UHP and HTST reduced by 14.89%,18.96% and 16.03%,18.62%,respectively,while the pH value,soluble solids and total acid contents in NFC juice changed little after UHP treatment,and color changed a lot after HTST treatment during storage. The bactericidal rate of UHP and HTST treatment on kiwifruit NFC juice were both 100%,but the microbial index of HTST treated NFC juice was lower than that of UHP treated during storage. The scavenging rates of NFC juice on free radicals of DPPH and ABTS were decreasing,for UHP and HTST treated juice in the fourth week,the values were 79%,74% and 78%,74% respectively. The types and contents of alcohols,esters in the aroma substances of NFC juice decreased(4.75%,2.53%)after UHP treatment,while the types and contents of ketones,aldehydes increased(6.10%,27.38%). After HTST treatment,the types of alcohols increased and the content decreased by 5.14% in the aroma substances of NFC juice,the types and contents of ketones,aldehydes increased(8.14%,26.39%). This research indicated that UHP treated NFC kiwifruit juice has a higher retention rate of color,nutrition,aroma and antioxidant activity at 4 ℃ for 3 weeks than that of HTST processing and maximally maintaining the quality of NFC kiwifruit juice. These results can provide an experimental basis for the process of NFC juice and the determination of NFC juice product shelf life.