Many outbreaks of foodborne disease in Korea have been attributed to the consumption of foods served in the foodservice. There is an increase in consumption of leaf and stem vegetables in school food service. Since leaf and stem vegetables are mainly used in uncooked menus, food poisoning accidents related with the consumption of leaf and stem vegetables are increasing every year.
The objectives of this study were (1) to investigate the factors affecting the microbial safety of leaf and stem vegetables in the high school foodservice and to provide information for supplying the safe menu in foodservice, (2) to evaluate the effect of slightly acidic electrolyzed water (SAEW) on the reduction of S. aureus, E. coli in lettuce, leek and baechu, and (3) to compare the risk of S. aureus and E. coli in washed lettuce, leek and baechu with various sanitizers using FDA-iRISK and The results of this study are as follows:
For the risk ranking analysis of leaf and stem vegetable menu, the lunch and dinner menu (1,945 data) of the total 6 high schools at the Central and the South Region in March, June, September, and December were collected. The frequency analysis and the multiple correspondence analysis (MCA) based on the 3 factors (potentially hazardous food (PHF), leafy and stem vegetables in the menu, the cooking methods) were conducted. The most frequent PHF served in menu was the blanched vegetables, salads, seaweeds and fried chicken. The most frequent consumed leaf and stem vegetables were spinach, chive, lettuce, Western cabbage, perilla leaf, iceberg lettuce, chicory, leek and broccoli. Multiple correspondence analysis (MCA) based on the leaf and stem vegetables, the region, and the cooking method (cooked/non-cooked) showed that garlic stem and spinach were more used in the Central Region, while water dropwort were more used in the South Region. Iceberg lettuce, Bok choy and leek were included frequently in the PHF menu. Plant products frequently used in PHF menu requires the food safety system such as Good Agricultural Practice (GAP) to reduce the microbial risk. The menu database according to raw materials based on cooking methods (heating or mixing) as well as the development and verification of menu based on the microbial safety will be contributed to provide the safer foodservice menu.
In the results of washing effect on the microbial reduction, S. aureus in lettuce decreased by 2.04, 2.01 log CFU/g in 70 ppm of SAEW and 100 ppm of NaClO, which was significantly higher than that of 30 and 50 ppm of SAEW. In general, the effect of washing with leek is low. However, the highest reduction effect of S. aureus with a decrease of 1.65 log CFU/g was observed with 70 ppm of SAEW. Furthermore, there was no significant difference in the concentration difference between 30 and 50 ppm of SAEW. Among the three vegetables (lettuce, leek and baechu), S. aureus in baechu showed the highest reduction by 2.83 log CFU/g when it was washed with 70 ppm of SAEW.
E. coli contaminated in lettuce was significantly reduced by washing with 70 ppm of SAEW (2.17 log CFU/g). Furthermore, E. coli in leek was more effectively reduced by washing than S. aureus in leek. Among them, when washed with 70 ppm of SAEW, E. coli in leek showed the highest decrease by 1.65 log CFU/g. In the case of baechu, E. coli decreased by 2.69 log CFU/g at 70 ppm of SAEW. The washing effect of SAEW on both S. aureus and E. coli in leaf and stem vegetables was superior with the concentration above 50 ppm SAEW.
According to the results of washing effect with leaf and stem vegetables and the FDA-iRISK output, the available chlorine concentrations (ACC) of SAEW 70 ppm are much lower than 100 ppm of NaClO, washing effect of 70 ppm SAEW was not significantly different from the washing effect or greater than that of 100 ppm NaClO. Therefore, SAEW, which is easy to use and adjust chlorine concentration accurately, can be applied to sanitize the raw vegetables in foodservice industry such as school or restaurant etc.