The Scope and Indicator Setting of Food Microbiological Testing

1. The scope of microbiological testing of food samples

The scope of food microbiological testing includes the following aspects:

① The testing of the production environment, including workshop water, air, floors, walls, operating floors.

② The testing of raw and auxiliary materials, including animal and plant food raw materials, food additives, packaging materials and other raw and auxiliary materials.

③ The testing of food processing, storage, sales and other links, including the health and hygiene status of employees, processing tools, pipeline equipment, transportation vehicles.

④ Food testing which includes the testing of intermediate products, factory food, suspicious food and the food that causes food poisoning.

2. The indicator setting of microbiological testing of food samples

Food microbiology testing indicators include total bacterial count, coliform group and pathogenic bacteria. The main indicators are as follows:

(1) Total bacterial count

The total bacterial count refers to the total number of bacterial colonies contained in 1g [1ml or 1cm(surface area)] food test samples after treatment and cultivation under certain conditions. The total bacterial count can reflect the freshness of the food, the degree of bacterial contamination and the general hygienic status of food production. Therefore, it is one of the important bases to judge the quality of food hygiene.

(2) Coliform group

Coliform group refers to a group of aerobic or facultative anaerobic gram-negative sporeless bacillus that can ferment lactose, produce acid and produce gas when cultured at 37℃ for 24 hours. These bacteria are resident flora in the intestines of human beings and warm-blooded animals, and are discharged from the body with their stools. The more the number of coliform groups in the food, the greater the degree of fecal contamination. Therefore, it is of wide significance to evaluate the hygienic quality of food with coliform group as the hygienic indicator of fecal contaminated food.

(3) Pathogenic bacteria

Pathogenic bacteria are the bacteria that can cause people to get sick. It is one of the essential standards in the food hygiene quality standards that pathogenic bacteria is not allowed to exist in food. Various kinds of pathogenic bacteria, different food processing and different storage conditions lead to the different contamination situations, so generally targeted tests are made according to the possible contamination conditions of different foods. Certain indicator bacteria are selected for testing for different foods. For example, Vibrio parahemolyticus is used as the indicator bacteria in marine products, salmonella, staphylococcus aureus and proteus are used as the indicator bacteria in eggs and egg products, bacillus cereus, proteus and mold are used as the indicator bacteria in rice and noodles, and heat-resistant sporeforms is used as the indicator bacteria in canned food.

(4) Molds and their toxins

Since there are many molds that can produce toxins and cause disease, toxigenic molds should be specifically tested, such as aspergillus flavus and aspergillus parasiticus that belong to aspergillus, penicillium citrinum and penicillium islandicum that belong to penicillium, as well as fusarium moniliforme and fusarium graminearum that belong to fusarium.

(5) Other indicators

Microbiological indicators should also include viruses, such as hepatitis virus, swine fever virus, Newcastle disease virus, Marek's disease virus, rabies virus, foot-and-mouth disease virus, swine vesicular virus and other viral microorganisms that have a direct relationship with human health, which are also indicators of food microbiological testing under certain circumstances. In addition, from the perspective of food testing, parasites have also been listed as an indicator of microbiological testing by many scholars.

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