Preparation and Quality Characteristics of Curd Yogurt Added with Chlorella

Yogurt base was prepared from skim milk added with $0.2{\sim}1.0%\;(w/v)$ chlorella powder and fermented with lactic acid bacteria (the mixed strain of Lactobacillus acidophilus, Bifidobacterium longum and Streptococcus thermophilus) at $40^{\circ}C$ for $12{\sim}18\;h$. Quality characteristics of the yogurt were evaluated in terms of acid production (pH and titratable acidity), number of viable cells, viscosity and sensory properties. The addition of chlorella powder stimulated the growth of lactic acid bacteria and remarkably enhanced the acid production. After 12 h incubation, titratable acidity of chlorella yogurt was $1.16{\sim}1.33%$ and was higher than that (1.02%) of yogurt made with only skim milk. However, the viscosity of yogurt was decreased by the addition of chlorella powder. The sensory score of yogurt added with 0.2% chlorella powder was similar to ordinary yogurt in taste and overall acceptability. When chlorella yogurt was kept at $4^{\circ}C$ for 15 days, its quality-keeping properties except for number of viable cells were relatively good. According to sensory score and storage ability, the optimum concentration of chlorella powder was around 0.2%.

클로렐라를 첨가한 요구르트의 제조와 품질특성

클로렐라를 첨가한 호상 요구르트의 제조를 위하여 탈지 분유에 Lactobacillus acidophilus, Bifidobacterium longum, Streptococcus thermophilus를 혼합한 균주를 접종하여 클로렐라의 첨가가 산의 생성, 젖산균의 생육 및 요구르트의 품질특성에 미치는 영향을 조사하였다. 클로렐라를 $0.2{\sim}1.0%(w/v)$ 첨가한 결과 산의 생성과 젖산균의 증식이 클로렐라를 첨가하지 않은 대조군보다 현저하게 증가되었으며, 12시간 발효시킨 요구르트의 적정 산도는 대조구의 1.02%에서 클로렐라를 1.0% 첨가한 경우 1.33%로 약 30% 증가하였다. 또한 클로렐라의 첨가로 요구르트의 점도는 $4{\sim}14%$ 감소하였다. 요구르트에 설탕을 10% 첨가하고 관능적 특성을 조사한 결과 클로렐라의 첨가가 요구르트의 기호도를 향상시키지는 못하였다. 클로렐라 요구르트의 저장성은 $4^{\circ}C$ 에서 15일간 저장 후 산생성과 pH는 거의 변화가 없었으나 생균수는 감소하였다. 전체적으로 클로렐라의 첨가량은 0.2% 수준이 적당한 것으로 나타났다.