CHANGES IN BITTERNESS, ANTIOXIDANT ACTIVITY AND TOTAL PHENOLIC CONTENT OF GRAPEFRUIT JUICE FERMENTED BY LACTOBACILLUS AND BIFIDOBACTERIUM STRAINS

Four strains of Lactobacillus and Bifidobacterium including L. plantarum 01, L. fermentum D13, L. rhamnosus B01725, and B. bifidum B7.5 exhibiting naringinase production were applied in grapefruit juice fermentation. All investigated strains grew well in grapefruit juice without nutrition supplementation. In all cases, cell counts were 10(8) 10(9) CFU ml(-1) after 24 hours of fermentation. The highest lactic acid and acetic acid productions were observed in the case of strain L. plantarum 01. The L. plantarum 01 and L. fermentum D13 strains prefer glucose over fructose and sucrose, whereas fructose was the most favoured sugar for L. rhamnosus B01725 and B. bifidum 137.5. At the end of the fermentation process, antioxidant activity and total polyphenol content of grapefruit juice decreased in all cases, but the changes were not significant. Significant decrease of naringin was observed in the case of L. plantarum 01, 28% naringin in grapefruit juice was removed after fermentation. This result is promising for development of technology for production of probiotic grapefruit juice.