酸馴化影響 Salmonella typhimurium 與 Bacillus cereus 在 牛乳乳酸發酵及產品中之生長與存活

Effect of acid adaptation on the growth and survival of Salmonella typhimurium and Bacillus cereus during the lactic fermentation of milk and product storage

沈宣汶(Hsuan-Wen Shen)

指導教授 ： 周 正 俊

國立臺灣大學/生物資源暨農學院/食品科技研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.01298

摘要

在本研究中乃先將Salmonella typhimurium及Bacillus cereus分別在pH 5.5與pH 6.3下進行1-4小時與40-90分鐘之酸馴化處理，然後探討酸馴化影響其於pH 4.0及pH 4.6之耐酸性，及其於Streptococcus thermophilus與Lactobacillus bulgaricus乳酸發酵牛乳過程中與商業及研究室試製發酵乳製品貯存於5℃時之存活性狀。
結果顯示在所測試之酸馴化無論處理之時間為何，均能顯著提高菌體之耐酸性，其中Sal. typhimurium以酸馴化4小時處理之效果最為顯著，而B. cereus則以酸馴化40分鐘者耐酸性提升之效果最佳。此外酸馴化處理也提高了Sal. typhimurium及B. cereus在乳酸菌發酵乳過程中及在市售及試製乳酸發酵乳貯存於5℃時之存活率。但在市售發酵乳產品貯存過程中，酸馴化對B. cereus存活率提高之幅度較小。將pH 5.5馴化4小時之Sal. typhimurium或 pH 6.3馴化40分鐘之B. cereus與未酸馴化 (控制組) 之Sal. typhimurium或B. cereus與Str. thermophilus或L. bulgaricus同時接種於脫脂乳並置於37℃下進行發酵，在發酵初期兩者菌數皆可迅速增加至約108-109 CFU/mL，其後菌數皆呈下降之現象，發酵48小時酸馴化Sal. typhimurium或B. cereus之存活菌數均高於控制組。將Sal. typhimurium或B. cereus接種於試製發酵乳或市售發酵乳製品中，並置於5℃下。在十日之貯存過程Sal. typhimurium及 B. cereus無論是否經過酸馴化，其存活菌數均隨貯存時間之延長而減少。惟酸馴化者存活之菌數亦呈現高於未酸馴化者之情形。此外，酸馴化亦能提升Sal. typhimurium及B. cereus對於低溫及發酵乳中可能含有其他抗菌物質之耐受性。

關鍵字

沙門氏桿菌 ； 仙人掌桿菌 ； 酸馴化 ； 乳酸發酵

並列摘要

In this study, Salmonella typhimurium and Bacillus cereus were subjected to acid adaptation at pH 5.5 for 1-4 h and pH 6.3 for 40-90 min, respectively. Effect of acid adaptation on the acid tolerance of Sal. typhimurium and B. cereus at pH 4.0 and 4.6, respectively, was first examined. Furthermore, growth and survival behavior of these pathogens during the lactic fermentation of skim milk by Streptococcus thermophilus or Lactobacillus bulgaricus and during the 10-day storage of laboratory-prepared and commercial dairy lactic fermented products at 5 ℃ were also investigated.
It was found that the acid adaptation, regardless the adaptation time, increased the acid tolerance of test organisms. The highest enhanced effect was noted for Sal. thphimurium and B. cereus after subjected to acid adaptation for 4 h and 40 min, respectively. During the lactic fermentation of skim milk, survival of acid-adapted cells of Sal. typhimurium and B. cereus was higher than the non-adapted cells. Similar phenomenon was also noted during the storage of laboratory-prepared and commercial lactic fermented product at 5 ℃. While acid-adapted cells of B. cereus showed a less magnitude of enhanced acid tolerance in the commercial lactic fermented products of milk during the storage period. In addition, acid adaptation may also enhance the tolerance of Sal. thphimurium and B. cereus to refrigerated temperature and other antimicrobial principles in fermented milk.

並列關鍵字

Salmonella typhimurium ； Bacillus cereus ； acid adaptation ； lactic fermentation

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