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Foodservice -- Cleaning and Sanitation

Can I stack washed dishes before they have completely dried?

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The Food Code requires that items must be allowed to air dry before being stacked or stored. Stacking wet items, such as pans and dishes, prevents them from drying and might allow an environment where microorganisms can begin to grow. Stacking dishes before they are dried is called wet-nesting. A study published in the Journal of the American Dietetic Association was conducted to determine if wet-nesting posed a potential hazard.

The study consisted of 100 randomly selected breakfast serving plates from the Veterans Affairs Medical Center in Portland, OR, on a randomly selected day. Samples of each plate were taken after excess water was removed for microbial testing. Fifty of the plates were washed in the dishwasher and immediately placed in stacks of 10 plates and allowed to sit 24 hours. Samples were then taken for microbial testing. The remaining 50 plates were also washed in the dishwasher. These plates were allowed to air dry separately for 24 hours. Samples were then taken for microbial testing.

Specific microorganisms were not identified in this study. NOTE: Many of the microorganisms detected were probably non-pathogenic. Results showed contamination in 95 of 100 plates before washing. After washing and the 24-hour drying period, there was no significant difference between the air-dried and wet-nested plates after 24 hours of incubation. However, after 48 hours of incubation, significant differences were found. After 24 hours, two wet-nested plates and four air-dried plates had bacterial growth. After 48 hours, 13 wet-nested plates and four air-dried plates had growth. This shows that wet-nesting may be a concern after long periods of time. This is of significant concern for foodservice operations that serve food in hospitals and to immunocompromised persons.

Wet-nesting can pose a problem if dishes sit for more than 24 hours. Therefore, it is important to implement preventive food safety practices as simple as proper handling of dishware.

SOURCE: Journal of the American Dietetic Association. Volume 101, No. 8, pp. 933-934

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