The effect of freeze-drying on microbial and chemical properties of cow and goat milk kefir
2004
Chen, H. C. | Lin, C. W. | Chen, M. J.
Kefir is fermented milk drink with sour and mild alcoholic flavour, and it contains a mixed microflora confined to a matrix of discrete kefir grains. Lactic acid bacteria and yeasts play the major roles in kefir grains. The purpose of this study was to investigate the effects of different lyoprotectants (galactose, lactose, maltose, sucrose and trehalose) and rehydrated media (water 4°C, 25°C: 10% reconstituted milk at 4°C, 25°C) on the viability of lactic acid bacteria and yeasts in freeze-dried kefir and increase the market value for this fermented milk product. Kefir was processed by cow and goat milk which was inoculated with 5% kefir grains, and incubated at 20°C for 20 hours. Different lyoprotectants were added independently before dehydration of kefir by freeze dryer. Results indicated that addition of galactose and sucrose as lyoprotectants significantly improved the viabilities of lactic acid bacteria and yeasts, however, there were no significant differences among rehydration treatments (P>0.05) for the viabilities of lactic acid bacteria. Both cow and goat milk had similar results in lyoprotectants and rehydration studies. As the above results, galactose and sucrose were selected as the lyoprotectants for kefir. The influences of concentrations of both lyoprotectants in viabilities and flavour of kefir were also studied. Results indicated addition of 7% sucrose provided a better lyoprotection for lactic acid bacteria and yeasts of freeze-dried kefir with good flavour after rehydration.
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