Effect of high intensity ultrasound on carbohydrate metabolism of bifidobacteria in milk fermentation

This study investigated the effect of high intensity ultrasound (20 kHz) on carbohydrate metabolism in milk fermentation by Bifidobacterium breve ATCC 15700, Bifidobacterium infantis, Bifidobacterium animalis subsp. Bifidobacterium lactis (BB-12), and Bifidobacterium longum (BB-46). After ultrasonication, lactose hydrolysis and the trans-galactosylation reaction in all fermented milk were accelerated during 24 h of fermentation. Lactose consumption of BB-46, BB-12, B. breve and B. infantis increased up to 2, 4, 3 and 2.5 times, respectively, in comparison with those found in control samples. This resulted in remarkable changes in the acid profiles of the strains. The ultrasonication stimulated the production of major organic acids in the later stage of the milk fermentation by BB-12, B. breve, and B. infantis, whilst it decreased the ratio of acetic acid to lactic acid and the ratio of total acetic and propionic acids to lactic acid in BB-12 and BB-46 samples, respectively.