Abstract
Microbial control is required for both quality maintenance and safety in foods. We examined the effectiveness of superheated steam (SHS) for sterilization of pathogenic and spoilage-causing bacteria in Chinese cabbage to be used for pickling (Asazuke). Raw Chinese cabbage harbored more than 5log CFU/g of viable cells, with the outer leaves exhibiting higher viable cell counts than the inner leaves. Most bacteria were found on the epidermal (surface) tissue and were not present in the inner tissue, which suggests that surface sterilization should be effective for microbial control in Chinese cabbage. Compared with the usual method of washing with sodium hypochlorite (NaClO), treatment with SHS was found to significantly reduce the population of microbes on Chinese cabbage without affecting texture or color tone. Populations of Gram-positive bacteria, Gram-negative bacteria, and nitrate-forming bacteria were found to decrease to less than 2.5log CFU/g. The effectiveness of SHS treatment in the sterilization of pathogenic bacteria was also evaluated. Treatment with SHS was found to reduce the populations of Escherichia coli O157 : H7 and Staphylococcus aureus in Chinese cabbage to below the detection limit. These results suggest that SHS treatment may be useful for microbial control when processing vegetables during pickle production.
