Fermentation Properties of the Mixed Yogurt Prepared with Bovine Milk and Soybean Milk

This experiment was carried out to examine the fermentation properties of yogurt prepared with bovine milk and soybean milk at the mixed ratios of 3:1, 2:1, 1:1, 1:2 and 1:3. The effect of bovine milk and soybean milk on promoting the fermentation was higher un pH was $3.75\~4.16$ when Lactobacillus salivarius ssp. salivarius CNU27, lactic culture 1(Lactobacillus delbrueckii ssp. bulgaricus(LB12)), Streptococcus salivarius ssp. thermophilus (ST36) and Lactobacillus acidophilus KCTC3150 were used. Titratable acidity was the highest when lactic culture 1[Lactobacillus delbrueckii ssp. bulgaricus(LB12), Streptococcus salivarius ssp. thermophilus(ST36)] was mea and the mixed ratio of bovine milk and soybean milk was 2:1. The average viable counts of lactic acid bacteria was the highest level of $2.17\times10^9$ cfu/ml when Lactobacillus salivarius ssp. salivarius CNU27 was used, and the mixed ratio of bovine milk and soybean milk was 1:3. the highest lactic acid production was 412.52mM when lactic culture 1[Lactobacillus delbrueckii ssp. bulgaricus (LB12), Streptococcus salivarius ssp. thermophilus (ST36)] was used, and the mixed ratio of bovine milk and soybean milk was 1:1. The production of acetic acid was the highest and the concentration was 394.01mM when lactic culture 2(Bifidobacterium longum, Lactobacillus acidophilus, Streptococcus salivarius ssp. thermophilus) was used and the mixed ratio of bovine milk and soy bean milk was 3:1. Tn the carbohydrate hydrolysis, stachyose was hydrolyzed $53.92\%$ as compared with the control when Lactobacillus salivarius subsp salivarius CNU27 was used, and the mixed ratio of bovine milk and soy bean milk was 1:3. The highest viscosity of yogurt was $1,300\~1,660$ cP when the mixed ratio of bovine milk and soybean milk was 1:3. The overall acceptability, $4.17\pm0.69$, was the highest when Lactobacillus acidophilus KCTC3150 was used and when the mixed ratio of bovine milk and soybean milk was 2:1.

우유와 두유를 혼합한 요구르트의 발효 특성

우유와 두유를 혼합하여 요구르트를 제조하고자 스타터에 따른 발효물의 성상을 시험하였다. 4종류의 서로 다른 스타터를 접종한 모든 처리구에서 배양 15시간 후 pH는 lactic culture 2(B. longum, L. acidophilus, S. thermophilus)를 제외한 나머지 처리구에서 $4.16\~3.75$ 사이로 나타나 발효 촉진효과가 있었고, 산 생성은 우유와 두유의 홉합비가 2:1이고 lactic culture 1 [Lactobacillus delbrueckii ssp. bulgaricus(LB12), Streptococcus salivarius ssp. thermophilus(ST36)]을 스타터로 사용한 요구르트에서 가장 높게 나타났다. 생균수는 1:3 비율에서 15시간째 Lactobacillus salivarius subsp. salivarius CNU27을 스타터로 사용한 균에서 $2.17\times10^9 cfu/mL$로서 최대 균수를 나타내었다. 두유 혼합요구르트에서 생산된 유기산의 함량을 측정한 바, 유기산 생산 중 lactic acid인 경우 lactic culture 1 [Lacto-bacillus delbrueckii ssp. bulgaricus(LB12), Streptococcus salivarius ssp. thermophihus(ST36)]을 스타터로 사용했을 때 1:1에서 412.52 mM로 가장 높았다. Acetic acid인 경우는 혼합비 3:1에서 lactic culture 2(B. longum, L. acidophilus, S. thermophilus)가 394.01mM로 가장 높게 생산되었다. 당 분해율은 혼합비 1:3에서 Lactobacillus salivarius subsp. salivarius CNU27를 스타터로 사용한 요구르트에서 대조구와 비교해 stachyose가 $53.92\%$로 가장 많이 분해되었다. 점도는 두유 혼합비가 가장 높은 1:3 처리구에서 $1,300\~1,660 cP$ 로 가장 높게 나타났다. 관능검사 결과는 2:1 혼합비에서 Lactobacillus acidophilus KCTC3150를 스타터로 사용한 요구르트가 $4.17\pm0.69,$ 3: 1 혼합비에서 Lactobacillus salivarius subsp. salivarius CNU27를 스타터로 사용한 요구르트가 $4.00\pm0..58$으로 기호도가 가장 좋은 것으로 나타났다.