Combined Treatments of Sodium Dodecyl Sulfate and Lactic Acid for Removal of Listeria Monocytogenes from Cabbage Leaves and Their Effects on Bacterial Cell Properties and Quality Characteristics of Fresh Cabbage

Tan, Yong Xiang (2025) Combined Treatments of Sodium Dodecyl Sulfate and Lactic Acid for Removal of Listeria Monocytogenes from Cabbage Leaves and Their Effects on Bacterial Cell Properties and Quality Characteristics of Fresh Cabbage. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

Text Tan Yong Xiang_Full Text.pdf Restricted to Registered users only Download (1MB)

Abstract

Listeria monocytogenes detected in the cabbages can cause foodborne illnesses due to lack of effectiveness of sanitizers in reducing surface microbial load but the potential of bacterial reattachment after washing and the antimicrobial mechanism of combination of SDS and lactic acid remain unclear. Therefore, this study aimed to investigate the efficiency of SDS, lactic acid and the combined treatment in removal of Listeria monocytogenes on cabbages, their antimicrobial activity, and effect on cell membrane integrity, aggregation and colour of cabbages. The treatments were applied on leaves inoculated with Listeria monocytogenes, followed by incubation at 30 °C for 1 and 24 hours. The antimicrobial activity, membrane integrity and cell aggregation were assessed by exposing cell suspensions to treatments. Bacterial log reductions on leaves were used to evaluate the efficiency of treatments. No significant differences were observed between treatments at 1 hour (4.0-6.0 log CFU/cm2), but synergistic effect was observed at 24 hours, with the combined treatments achieving a reduction of 6.8 log CFU/cm2, as compared to SDS (2.2 log CFU/cm2) and lactic acid (3.8 log CFU/cm2). For antimicrobial activity, the combined treatment led to highest log reduction, followed by lactic acid and SDS, but no significant differences. The combined treatment led to the lowest membrane integrity, followed by lactic acid and SDS. SDS decreased the cell aggregation from about 31.7 % to 14.3 % but lactic acid increased it to 88.7 %. Lactic acid significantly increased b* from 7.9 to 12.2, whereas the combined treatment significantly decreased L* from 78.9 to 74.1. Despite colour changes, the combined treatment showed high log reduction likely due to membrane damage, along with lower reattachment, suggesting potential in reducing surface microbial load. Keywords: Listeria monocytogenes, cabbages, decontamination, surfactants, organic acids.