Abstract

The effects of various nutrients added to soy protein concentrate (SPC)-yogurt on the growth of Lactobacillus acidophilus and the flavor of SPC-yogurt were investigated. Soy milk was prepared from SPC (4.2% as protein) and various nutrients. One hundred ml of the prepared soy milk was given proper heat treatment, inoculated with 2.5ml of 24 hr-old culture, and incubated for 24 hr at $37^{\circ}C$. The growth of L. acidophilus was estimated from viable cell counts, titratable acidity and pH. The growth curve obtained from the experiment suggested that the log phase ended after 6 hr and the stationary phase ended after 30 hr. Glucose and fructose greatly enhanced the acid production by L. acidophilus. The optimum concentration of these two sugars in the media was approximately 3% each. Yeast extract greatly stimulated the acid production by L. acidophilus, and the optimum concentration of this additive was approximately 0.5%. Higher concentration of SPC resulted in slightly higher acidity in soy yogurt.

본 연구에서는 SPC-yogurt에 첨가되는 여러가지 당(糖)과 발육촉진물이 L.acidophilus의 생육에 미치는 영향을 관찰하고, 제조된 yogurt의 flavor를 조사하였다. Soy milk를 SPC(단백질 4.2%)와 여러가지 당(糖) 및 발육촉진물질로 제조하였고 준비된 Soy milk 100ml를 적절히 가열살균후 24시간 배양된 유산균 2.5ml를 접종하고 $37^{\circ}C$에서 24시간 배양하였다. 유산출 생육의 정도는 생균수, 산도, pH로 판단하였다. 배양시간에 따른 유산균의 생육도를 측정한 실험으로부터 6시간까지가 log phase이고 30시간까지가 stationary phase인것으로 나타났다 본 실험에서 사용된 당(糖) 가운데 glucose와 fiuctose가 유산균에 의한 산생성에 현저한 효과를 보였으며. 그 적정농도는 가각 3%정도였다 첨가된 발육촉진물질가운데 yeast extract가 유산균에 의한 산의 생성을 가장 촉진시켰으며 그 적정 농도는 0.5% 정도였다 SPC의 농도가 증가함에 따라 제조된 soy yogurt의 산도가 다소 증가하였다.

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