Food Microbiological Detection Methods

In our daily lives, we eat a lot of food, and among these foods, not only are there foods we make at home, but also a lot of food that is purchased. When it comes to purchased food, what people are more worried about is the quality. In fact, these foods need to pass microbial testing before they appear on the market. Food microbial testing mainly tests the number of bacteria and bacterial flora.

1. Sample Pretreatment

Compared with the traditional manual operation mode and reusable homogenizers and stirring blades, there are now a wide variety of disposable homogenizing bags, beating homogenizing systems isolated from samples, and automated weight gradient dilution instruments on the market, which not only realize the automation, standardization and batch production of sample pretreatment, but also avoid cross contamination between samples.

2. Bacterial enrichment and isolation

Regardless of traditional methods or modern detection technology, due to the limitation of detection sensitivity, food samples often need to undergo bacterial enrichment culture and selective separation after pre-treatment before they can be used for subsequent detection and analysis. In traditional microbial testing, the above two steps take up to 24-96 hours and are the key rate-limiting steps in the entire testing process. Therefore, establishing efficient bacterial enrichment strategies and target-specific microbial concentration and separation systems has become the core of achieving rapid microbial detection.

3. Sample Processing

Sample processing should be carried out in a sterile room. Frozen samples must be thawed in the original container in advance. The thawing temperature should be 2-5℃ for no more than 18 hours or 45℃ for no more than 15 minutes.

4. Inspection

Each indicator has one or several testing methods, and the appropriate testing method can be selected according to different foods and different purposes. The conventional inspection methods commonly used are the current national standards, or international standards (such as FAO standards, WHO standards, etc.), or the standards of the food importing country (such as the US FDA standards, the Japanese Ministry of Health, Labor and Welfare standards, the European Community standards, etc.).

When the food hygiene and microbiology testing laboratory receives an inspection application form, it should immediately register it, fill in the test number, and immediately place the sample in the refrigerator or ice box according to the inspection requirements, and actively prepare conditions for the inspection.

Generally, the sample can only be processed 3 days after the positive sample is issued (it can be extended appropriately under special circumstances); positive samples of imported food need to be stored for 6 months before they can be processed. Negative samples can be processed promptly.

5. Reporting of results

After the sample inspection is completed, the inspector should fill out the report form in a timely manner, sign it, and send it to the supervisor for verification and signature, affix the company seal to indicate that it is effective, and immediately hand it over to the food hygiene supervisor for processing.