Impact of Food Contact Surface on Biofilm Formation by L. Monocytogenes in Different Concentration of Watermelon Extract

Soh, Ai Fong (2019) Impact of Food Contact Surface on Biofilm Formation by L. Monocytogenes in Different Concentration of Watermelon Extract. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Growth and biofilm formation of L. monocytogenes at different concentration of watermelon flesh extract on different food-contact surface was studied. Stainless steel and polypropylene coupons were used for development of biofilms for 1, 4, 6, 8, 24, 48, 72 and 96 hours in 100 mg/ml and 5 mg/ml watermelon extracts. In higher concentration of nutrient, the biofilm formation was greater than that in lower concentration of nutrient. Biofilm formation of L. monocytogenes on stainless steel was greater in comparison to polypropylene. For 100 mg/ml of watermelon extract inoculated with 6 log CFU/ml, the number of L. monocytogenes cell in biofilm communities was 8.26 log CFU/cm2 on stainless steel coupon and 8.15 log CFU/cm2 on polypropylene coupon in 96h. For 5 mg/ml of watermelon extract inoculated with 6 log CFU/ml, the number of L. monocytogenes cell in biofilm communities was 7.43 log CFU/cm2 on stainless steel coupon and 7.02 log CFU/cm2 on polypropylene coupon in 96h. This study showed that L. monocytogenes can grow at very low concentration of nutrients from watermelon extract and subsequent form biofilm on different foodcontact surfaces. Keywords: L. monocytogenes, biofilm formation, watermelon extracts, stainless steel surface, polypropylene surface