Efficacy of household washing pre-treatments and cooking methods for reduction of listeria monocytogenes in artificially contaminated chicken offal

Consumption of chicken offal is common and famous among Malaysians as it is often served as one of the side dishes with rice. Chicken offal can be a potential source of Listeria monocytogenes because slaughtered animals are recognized as a reservoir for foodborne pathogens. L. monocytogenes is a dangerous foodborne pathogen which can cause severe foodborne listeriosis with high fatality rate. This study aimed to determine the efficacy of different washing pre-treatment and cooking methods to reduce L. monocytogenes in artificially contaminated chicken offal. All the washing pre-treatments (dip treatment in different water sources and wash treatment with different water flow rates) showed significant reduction of the pathogen (p<0.05) when the inoculated samples were treated from 2 mins onwards. Washing the inoculated samples under the water flow rate of 2 L/min was the most effective way to reduce the number of L. monocytogenes (approximately 1.97 log reduction after washing for 10 mins). For heat treatment study, deep-frying was the most effective cooking method followed by boiling and pan-frying to reduce L. monocytogenes where all L. monocytogenes cells (7.91 log₁₀ CFU/g) were killed within 45 s under deep-frying treatment. Overall, the study indicated that washing under running tap water (2 L/min) and deep-frying was effective in reducing and controlling the microbial populations during food preparation. The findings from this study can serve as a safe preparation step and cooking guideline. It is necessary to implement safe steps in food handling practices among food handlers to minimize the risk of foodborne infection.