The study of carbohydrates fermentation ability of B.lactis in milk
2011
Beitane, I., Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Food Technology | Ciprovica, I., Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Food Technology
The ability of Bifidobacterium lactis (Bb-12) to hydrolyse lactose, lactulose and inulin was studied during milk fermentation. For this purpose, the content of lactose, lactulose and inulin was determined before and after fermentation of milk samples. Pasteurized milk, freeze-dried culture Bb-12 (Chr. Hansen, Denmark), inulin - RAFTILINE®HP (ORAFI, Belgium) with polymerization degree ≥5 and degree of purity 99.5%, syrup of lactulose (Duphalac®, the Netherlands) were used for experiments. The different concentrations (1; 2; 3; 4 and 5%) of lactulose and inulin were used for studying of B.lactis ability to assimilate of milk sugar and prebiotics during fermentation. The fermentation process of milk samples enriched with lactulose or inulin was produced at 37 deg C for 16 hours. The content of lactose and lactulose was determined by IDF standard 147B:1998 procedure, the content of inulin by AOAC Official Method 999.03 and by AACC Official Method 32.32. Results showed that bifidobacteria poorly assimilate lactose at the presence of prebiotics in milk. The lactose assimilation decreases together with increase of added prebiotics concentration in milk. However bifidobacteria are able to hydrolyse up to 50% of lactulose in the product, except sample with 5% of lactulose. There was a decrease of lactulose by 2/3. The changes of lactulose content are significant (p is less than 0.05). Consequently B.lactis possesses ability to assimilate lactulose. Inulin assimilation degree in fermented milk samples was low (10–20%), because it depends on the inulin polymerization degree and the degree of purity. The inulin assimilation decreases together with the increase of inulin polymerization degree and the degree of purity. The obtained results confirm that most suitable substrate for growing of bifidobacteria in milk is lactulose at any analyzed concentration.
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