Behaviour of Acid-Adapted Listeria Monocytogenes in Pasteurized Red Dragon Fruit Juice and Guava Juices under Different Storage Temperatures

Lee, Shao Fang (2018) Behaviour of Acid-Adapted Listeria Monocytogenes in Pasteurized Red Dragon Fruit Juice and Guava Juices under Different Storage Temperatures. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Listeria monocytogenes is a causative pathogen of Listeriosis infection. In this study, Listeria monocyotogenes was subjected mild acid condition (pH5.7) in Tryptic Soy Agar (TSB) for acid tolerance response induction. Red dragon fruit and guava fruit juice (pH 3.5) were inoculated with both acid-adapted and non-acid adapted cells of L. monocytogenes then incubate at 4°C and 37°C of storage temperatures. The result of this study showed a higher survival rate of acid-adapted cells due to the development of acid habituation as cross-protection in lethal acid condition with both storage temperatures compared to non-acid adapted cells. Comparison among 2 storage temperatures, result does not shown a significance difference. However, acid-adaptation and low temperature do enhance the survival of cells against acid stress. Acid adapted cells has higher survival rate in every single treatments in this research. Besides, acid adapted cells in red dragon fruit juice and guava juice less than 4°C were fall within the range of 10.08±0.05 to 11.23±0.03 log cfu/ml and 5.65±0.07 to 6.75±0.09 log cfu/ml which is much higher than both juices under storage temperature of 37°C. Evidence of this study presented that ATR established cross-protection against lethal acid condition and enhanced the bacteria growth. Further study should be continued with different fruits and storage temperatures as it will promote to outbreak of listeriosis that will destroy human health.