Bifidobacterium lactis HN019: survival, acid production and impact on sensory acceptance of fermented milk
2019
Oliveira, L. G. S. | Macedo Jr, F. | Miglioranza, L. H. S. | Spinosa, W. A. | Henrique-Bana, F. C. | Costa, G. N. | Takihara, A. M.
Bifidobacterium lactis HN019 was monitored for its viability and acid production during milk fermentation and cold storage. Milk was fermented for 72 h at 37°C, and the shelf life of the resulting probiotic milk was evaluated at 4°C for 30 d. Additionally, lactic and acetic acids and lactose contents during the fermentation were measured by in situ quantitative proton nuclear magnetic resonance spectroscopy (isq ¹H NMR), and the sensorial acceptance of the fermented milk was evaluated by 80 panellists. The pH of the milk fermented by B. lactis HN019 reduced from 6.36 to 3.97 after 72 h incubation. The viability of the evaluated strain was maintained above 9.21 up to a decrease to 8.85 log CFU/mL after 48 h fermentation. With respect to metabolism, isq ¹H NMR revealed that the acetic and lactic acid contents increased from 0.47 ± 0.06 g/L to 16.36 ± 1.86 g/L and 2.59 ± 0.10 g/L to 9.40 ± 0.18 g/L, respectively, indicating high production of acetic acid by HN019 during the 72 h fermentation. On the other hand, lactose content decreased throughout the fermentation period. In fact, strain HN019 showed a high content of acetate throughout fermentation; however, exhibited the stability required in fermented milks with high viable cell counts and low activity of post-acidification during the shelf life. In sensory evaluation, the panellists preferred the probiotic milk fermented for 8 h because after 72 h the acetic flavour was already perceptible.
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