酸馴化與未酸馴化仙人掌桿菌在脫脂牛乳乳酸發酵過程及產品貯存於5° C 時之活性   全文下載

Viability of Acid-adapted and Non-adapted Bacillus cereus during the Lactic Fermentation of Skim Milk and Product Storage at 5°C

在本研究中先將仙人掌桿菌（Bacillus cereus）置於pH 6.3 進行40min 之酸馴化處理。經酸馴化之仙人掌桿菌在pH 4.6 酸性環境下之存活百分率比未酸馴化者為高。以Streptococcus thermophilus 或Lactobacillus bulgaricus 進行脫脂牛乳乳酸發酵過程中之前12-18 hr，酸馴化及未酸馴化之仙人掌桿菌之活菌數皆迅速增加至約108-109 CFU/mL，其後均呈下降之情形。惟酸馴化者菌數下降之速度比未酸馴化者低。接種仙人掌桿菌於Str. thermophilus 發酵之脫脂牛乳及兩種市售發酵乳製品並置於5° C 下貯存，酸馴化之仙人掌桿菌比未酸馴化者顯示有較高之活菌數。酸馴化降低了仙人掌桿菌對酸度、冷藏程度及發酵乳中可能含有有害因子之敏感性。

In this study, Bacillus cereus was subjected to acid adaptation at pH 6.3 for 40 min. It was found that acid-adapted B. cereus exhibited a higher survival percentage than non-adapted cells after exposure to an acidic condition of pH 4.6. The viable population of both acid-adapted and non-adapted B. cereus increased during the first 12-18 hr of lactic fermentation of skim milk by Streptococcus thermophilus or Lactobacillus bulgaricus, and then declined as the fermentation extended. However, the acid-adapted cells exhibited a lower population reduction rate than the non-adapted B. cereus. A higher viable population of acid-adapted B. cereus than the non-adapted cells was also noted in Str. thermophilus-fermented skim milk and the two commercial lactic fermented products kept at 5°C. Additionally, the acid adaptation could reduce the susceptibility of B. cereus to acidity, refrigerated temperature and other detrimental principles present in lactic fermented milk products.