Quality properties, flavor and hypoglycemia activity of Kiwifruit-Bitter gourd fermented milks

In this study, kiwifruit-bitter gourd juice was added to reconstituted milk at 5%, 10% and 15% (v/v) to prepare fermented milk (KBFM5, KBFM10 and KBFM15). Fermented milk without kiwifruit-bitter gourd juice was used as control fermented milk (CFM). Compared with CFM, the viable counts of Streptococcus thermophiles (St) in KBFM5, KBFM10 and KBFM15 were increased by 4.5%, 6.5% and 5.9%, Lactobacillus bulgaricus (Lb) were increased by 2.9%, 7.1% and 4.3%, and Bifidobacterium adolescentis (Ba) were increased by 9.0%, 11.5% and 10.7%, respectively. The value of initial titratable acidity (TA) of CFM was 82.4°T, the TA values of KBFM5, KBFM10 and KBFM15 were increased by 3.5%, 6.4% and 5.7%, respectively. Compared with CFM (water-holding capacity (WHC) was 79.69%; syneresis value was 324.3 g/kg), WHC of KBFM5, KBFM10 and KBFM15 were increased by 2.2%, 14.8% and 7.1%, and the syneresis values were reduced by 9.7%, 11.3% and 10.7%, respectively. The firmness value of CFM, KBFM5, KBFM10 and KBFM15 was 22.71, 26.84, 27.90, 23.56 g, the cohesiveness value was 126.92, 139.82, 153.56, 132.82 g/s, the consistency value was 13.38, 16.36, 18.38, 14.58 g, and the index of viscosity was 4.93, 7.56, 9.29, 6.16 g/s, respectively. KBFM10 has highest sensory scores (37.96-maximum 40) which was selected for investigation of volatile compounds and hypoglycemia activity. Thirty-six kinds of volatile compounds were identified in KBFM10 and thirty kinds in CFM, which were mainly aldehydes, alcohols, acids, ketones, and esters. During 28 day refrigerated storage, the values of α-glucosidase inhibition of CFM was 21.6%, 30.27%, 26.61%, 24.59%, 22.82%. The values α-glucosidase inhibition of KBFM10 was respectively increased by 28.61%, 34.13%, 38.67%, 36.07%, 37.77%. This study demonstrated that kiwifruit-bitter gourd juice can be added as an active ingredient in milk preparations to provide novel functional dairy products.