if you are satisfied, please adopt

Sampling

to extract a small number of representative samples from the products for inspection and analysis. This process is called sampling.

1. Principles of sampling for food inspection

1. Some preparatory work before sampling

- dry ice: refrigerant. You can also use wet ice

–box or refrigerator: storing and transporting samples.

–Sterilization containers: from plastic bags to sterilized gallon paint barrels.

- sampling tools: teaspoons, angle spoons, needle-nosed pliers, tweezers, measuring cylinders and beakers.

- Sterile gloves:

- Sterile cotton swab: generally used to swab instruments and facilities and factory environment areas.

–Sterilized full packaging bag: for samples. When the sample is collected, the conditions of sample collection, such as the temperature and location of the product, together with the sample number, are recorded in the inspector's notes. When collecting sterile samples, one of the most important rules is: never pollute the samples. This requires the sample collector to collect all additional samples very carefully to ensure that this rule is not violated.

2. Principles of food sample collection

1) The samples taken should be representative.

2) sampling must meet the requirements of aseptic operation to prevent all external pollution

- one appliance can only be used for one sample to prevent cross-contamination.

3) During storage and transportation, the state of microorganisms in the samples should be kept unchanged

- collected non-frozen foods are generally refrigerated at 1 ~ 5℃, and foods that cannot be refrigerated should be inspected immediately. Generally, the inspection is carried out within 36h.

4) The sampling label should be complete and clear

–the label of each sample should be clearly marked, providing as detailed information as possible.

II. Sampling methods of food inspection samples

I) Sampling scheme

Generally speaking, if the import and export trade contract clearly stipulates the sampling quantity of food, the sampling shall be carried out according to the contract; If there are no specific sampling regulations, the sampling scheme can be determined according to the inspection purpose, the nature of the product and the sampled product and the analysis method.

At present, the most popular sampling schemes are the sampling scheme recommended by ICMSF and the random sampling scheme.

no matter what sampling method is adopted, the sampling quantity of each batch of goods shall not be less than 5 pieces. For foods that need to be tested for Salmonella, the number of samples should be increased appropriately, with a minimum of 8 pieces.

ii) sample selection

iii) sampling (sampling) method

international commission on microbiological specifications for foods, ICMSF

ICMSF method is considered from a statistical point of view. How many samples should be checked for a batch of products in order to be representative and objectively reflect the quality of the batch of products?

The basic sampling principle proposed by p>ICMSF is to specify different sampling numbers according to the following considerations:

(1) Various microorganisms themselves have different degrees of harm to people;

(2) After food is treated under different conditions, its harm degree can be divided into three situations: the harm degree decreases; The degree of harm has not changed; The degree of harm increases.

ICMSF classifies the hazard degree of microorganisms in food by integrating the hazard degree of microorganisms, the characteristics of food and processing conditions. This idea is very scientific, conforms to the actual situation, and is reasonable for manufacturers and consumers.

sampling scheme of ICMSF: ICMSF method includes two types: two-level method and three-level method. The second-level method only has n, c and m values, and the third-level law has n, c, m and m values.

–n: refers to the sampling number of a batch of products. C: refers to the number of samples in this batch of products with the number of samples exceeding the limit.

–m: refers to the limit of qualified bacteria. M: refers to the limit of the number of bacteria determined to be qualified after additional conditions are attached.

Use the two-level sampling scheme in the case of moderate or serious hazards, and suggest using the three-level sampling scheme in the case of low health hazards.

1) Two-level method:

Only the M value of the eligibility criteria is set, and if it exceeds the M value, it is a nonconforming product. Whether the batch is qualified or not can be judged by checking whether there are any samples that exceed the m value.

if the total number of bacteria in raw fish fillets is n=5, c=1 and m = 111 cfu/g. Where m=111cfu/g is the limit standard, n=5 is five samples, and c=1 means that among the five samples in this batch, if no samples with a value of more than 111cfu/g are found, this batch of products is qualified.

cfu: colony forming unit, colony forming unit

2) Three-level method:

Microbial standard values M and M values are set, just like the two-level method, and samples exceeding M values are considered as unqualified. All samples are less than m value, and this batch of products is qualified; The number of samples in the range of M value to M value is within the range of C value, which means that the additional conditions are qualified, otherwise it is unqualified; Where any sample exceeds the m value, the batch of products is unqualified.

For example, the coliform standards of frozen sugar foods in Australia are n=5, c=2, m=111 and M=1111, which means that five samples are taken from a batch of products, and if the coliform results of all samples are less than m=111, the batch of products is judged to be qualified; If the results of ≤2 samples are between m and m value (that is, between 111 and 1111), it is determined that the additional conditions are qualified; If the results of three or more samples are between m and m, it is determined that the batch of products is unqualified; If the coliform count of any sample exceeds M value (i.e. 1111), the batch of products is judged to be unqualified.

table 3-1 ICMSF is classified according to the degree of microbial hazard and food processing

ii) sample selection

sample selection can be divided into targeted selection and random selection.

1. When sampling on site, random sampling table can be used for random sampling.

2. Targeted selection is to collect samples according to the known situation, such as suspecting that a certain food may be the cause of food poisoning, or preliminarily judging that the food has hygienic quality problems.

iii) sampling (sampling) method

random sampling, that is, using a method that can make every part of the population appear in the sample equally, several parts are extracted from a large number of samples.

representative sampling (targeted sampling), that is, sampling by systematic sampling method, so that each part taken represents the corresponding part of food.

The random sampling table is randomly compiled by computer, including 1,111, 1,111 or 1,111 digits. The use method is as follows:

a. First, the products of each unit of a batch of products (such as boxes, bags, boxes, etc.) are numbered in sequence. For example, a batch of 611 packs of products is numbered as 1, 2 ... 611.

B. randomly point out a number on the table. Look at the row and column where the number is. For example, click on the numbers in row 18 and column 11.

C. according to the maximum number of digits of the unit product number (for example, the maximum number is three digits), the continuous column number of the line is found, and the unit product with the same number is a sample to be taken.

D. continue to look up the same consecutive column numbers in the next row. The unit product represented by this number is another sample that should be taken.

e. follow the above methods in turn. When the number checked exceeds the maximum number, this number will be discarded, and the number of the same column in the next row will continue to be checked until the number of products to be sampled is completed.

3) Sampling (sampling) method

1) Gravimetry takes a certain weight of food as a sample. After slaughter, the medial muscle of both legs or the longest muscle of the back was taken as 1.11 g/animal; Samples of eggs and egg products, not less than 211g each.

2) swab sampling does not damage the integrity of meat and is easy to operate. However, the total number of live bacteria detected is not high.

3), lavage method It is best to take samples immediately after washing for all clean-bore birds. This method has higher detection rate than swab method.

the sampling method is very important for the effective implementation of the sampling scheme and ensuring the validity and representativeness of the samples.

sampling must follow aseptic operation procedures, and sampling tools such as stainless steel spoons, tweezers and scissors should be autoclaved to prevent all possible external pollution. The container must be clean, dry, leak-proof, wide-mouthed and sterilized, and the size is suitable for holding samples. During the whole sampling process, necessary measures should be taken to prevent the number and growth ability of inherent microorganisms in food from changing. Attention should be paid to the homogeneity and source of products to ensure the representativeness of samples.

Sample preparation in microbiological examination Uniform food: divided by quartering method; Meat and aquatic food: cut with sterilized scissors, and split by quartering.