Observation of lactic acid bacteria and yeast populations during fermentation and cold storage in cow's, ewe's and goat's milk Kefirs

Changes in the population numbers of Lactobacillus spp, Lactococcus+Leuconostoc spp. and yeasts in the kefirs made of cows, ewes and goats milk were determined in this study. The highest count of Lactobacillus spp. was in ewe's milk. There was a slight or no difference in the goats and cow's milk. At 24 h, one log10 cfu/ml decrease was observed for Lactobacillus spp. in cows and ewes milk. Lactobacillus spp. were more steady in goat milk with a half log10 cfu/ml decrease. Lactococcus+Leuconostoc spp. similarly reached their maximum populations in cow, ewe and goat milk at the time period of 15-24 h. Lactococcus + Leuconostoc spp. in all milks were in parallel with the maximum populations of Lactobacillus spp. in ewe milk at the time period of 12-15 h. Yeasts had similar numbers in cow, ewe and goat milk at the time period of 15-21 h. Some decreases were observed in the numbers of Lactobacillus spp, Lactococcus+Leuconostoc spp, and yeasts of the kefirs kept at 4ºC for 7 days. The decreases of Lactobacillus spp. in cows' and goats' milk kefirs were slight and similar, while one and half log10 cfu/ml decrease was counted in ewes' milk kefir. The decrease in the numbers of Lactococcus+Leuconostoc spp. was more pronounced than those of Lactobacillus spp. and yeasts. pH decreased during the fermentation and all remained constant over the storage period of 7 days. The type of milk had an influence on the population development of kefirs. Ewe's milk supported the growth of Lactobacillus spp. and Lactococcus+Leuconostoc spp. better. This indicates that different milks may influence the population development of kefir microflora which may affect the quality of kefir. Bu çalışmada, inek, koyun ve keçi sütünden yapılan kefirlerde Lactobacillus spp, Lactococcus+Leuconostoc spp. ve mayaların popülasyon düzeyindeki değişim belirlendi. En yüksek Lactobacillus spp. düzeyi koyun sütünde saptandı. Keçi ve inek sütünde ise çok az veya hiç fark yoktu. Yirmi dördüncü saatte inek ve koyun sütünde Lactobacillus spp. için bir log10 cfu/ml azalma gözlemlendi. Lactobacillus spp. keçi sütünde yarım log10 cfu/ml azalma ile daha istikrarlıydı. Lactococcus+ Leuconostoc spp. benzer olarak maksimum popülasyonlarına inek, koyun ve keçi sütünde 15-24 saatlik zaman periyodunda ulaştı. Lactococcus+Leuconostoc spp. bütün sütlerde, Lactobacillus spp.'nin koyun sütünde 12-15 saatlik zaman periyoundaki maksimum popülasyonu ile parelellik içersindeydi. Mayalar inek, koyun ve keçi sütünde 15-21 saa