The sample retention time is not less than 48 hours. The national food safety standard "General Hygienic Specification for Catering Services" stipulates that the sample retention amount per meal or batch shall not be less than 65438 0.25 g, and the sample retention time shall not be less than 48 hours. This standard stipulates that centralized dining units such as canteens in schools (including kindergartens), canteens in old-age care institutions, canteens in medical institutions, canteens in construction sites, and catering service providers such as central kitchens, collective dining distribution units, and one-time collective dinners 100 people or more shall keep samples of perishable food in accordance with regulations. According to the requirements of three-level sampling for microbiological examination, the sample retention for each meal or batch of perishable food should be no less than 125g, and the sample retention time should be no less than 48 hours.