熱震處理影響Streptococcus thermophilus在後續致死環境壓力下之存活

Effect of Heat Shock on the Survival of Streptococcus thermophilus Under Subsequent Lethal Stresses

李盈萱(Ying-Hsuan Lee)

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(2013年)

https://doi.org/10.6342/NTU.2013.01195

摘要

Streptococcus thermophilus為耐熱性乳酸菌，常用於酸凝乳及一些起司之發酵上當作菌酛。本研究乃在探討發酵菌酛S. thermophilus BCRC 14085在次致死溫度處理 (熱震) 後，在後續一些致死壓力環境下如在高溫、酸性、凍藏、高滲透壓、乙醇、有機酸及噴霧乾燥與冷凍乾燥、模擬腸胃道環境下之菌體耐受性的影響。
結果顯示熱震處理能夠提升菌株S. thermophilus BCRC 14085在58℃下之耐受性，在所試之熱震條件中，以50℃熱震處理30分鐘提高其耐熱性之效果最為顯著。此外，熱震處理也顯著提高S. thermophilus BCRC 14085在後續酸性 (pH 2.5)、冷凍 (-20℃)、乙醇 (25% v/v)、高滲透壓 (aw ca. 0.75) 及含有機酸 (0.75 M乳酸、醋酸、檸檬酸，pH 3.5) 等致死環境下之耐受性。此外，熱震處理也能顯著提升S. thermophilus BCRC 14085在模擬噴霧乾燥及模擬腸胃道 (pH 2.5~3.0及2%膽鹽濃度) 環境下之存活率 (p ＜ 0.05)。

關鍵字

Streptococcus thermophilus ； 熱震效應 ； 交叉保護作用

並列摘要

Streptococcus thermophilus is a thermophilic lactic acid bacteria which was commonly used as the starter organism of yoghurt and some cheese. In the present study, S. thermophilus BCRC 14085 was first subjected to sub-lethal heat treatments (heat shock). Its survival in subsequent lethal stress environments such as high temperature, freezing storage, acidic (pH 2.5) environment, high osmotic pressure, ethanol, organic acid, drying process (spray drying and freeze drying) and simulated gastrointestinal juice were investigated.
Results revealed that heat shock treatments increased the thermal tolerance of S. thermophilus BCRC14085 at 58℃. Heating at 50℃ for 30 min, among the various heat shock treatments examined, was found to enhance the thermal tolerance most profoundly. Besides, heat shock enhanced the survival of test organism exposd to high osmotic pressure (aw ca. 0.75), acid (pH 2.5), 25% ethanol, frozen storage (-20℃) and organic acidic (0.75 M lactate, acetate and citrate, pH 3.5). Furthermore, heat shock was also noted to increase significantly (p < 0.05) the survival of S. thermophilus subjected to spray drying process or exposed to simulated gastrointestinal juice (pH 2.5-3.0 and 2% bile salt).

並列關鍵字

Streptococcus thermophilus ； heat shock ； cross-protection

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