1、 Detection significance and core basis

• Hazard essenceIndustrial alkali (caustic soda, caustic soda) has a strong dissolving effect on proteins and can artificially improve the fullness and weight of water-based products. However, heavy metals such as lead and arsenic, as well as harmful impurities, can cause gastrointestinal symptoms such as discomfort and vomiting. Long term consumption may damage liver and kidney function.

• Regulatory requirementsThe state explicitly prohibits the use of industrial alkali in food processing; The standard for "Pollution free Food - Water based Aquatic Products" stipulates that the pH value of water based aquatic products must be ≤ 8, and exceeding the pH value is an important signal suspected of adding industrial alkali.

2、 Preparation of testing tools

3、 Operation process and result judgment

The detection is carried out in two steps. First, the pH value is screened, and the second step is to accurately identify the samples that exceed the standard, ensuring detection efficiency and accuracy.

Firstly, pH value screening (core initial inspection stage)

1. Conventional samplingCollect the soaking solution of water-based products (if it is a bulk product, directly take the soaking liquid; if it is a packaged product, soak the product in purified water for 5 minutes and take the soaking solution).

2. Test paper detectionTake out a pH test strip, immerse it in the soaking solution, let it sit for half a second, then quickly remove it. Within 30 seconds, compare it with a standard color plate and read the pH value.

3. Special case handlingIf the soaking solution cannot be obtained, directly stick the pH test paper on the surface of the moist aquatic product, and compare the color chart after 30 seconds; If the test strip shows a pH value greater than 8, immediately soak the sample in 5mL of purified water for 3 minutes, and take the soaking solution for subsequent testing.

4. Initial screening resultsIf the pH value is ≤ 8, it is judged as passing the initial inspection and no further operation is required; If the pH value is greater than 8, it is judged as unqualified in the initial inspection, and the second step of industrial alkali identification must be carried out.

Step 2: Precise identification of industrial alkali (for samples that fail the initial inspection)

1. Sampling operationSuck 1mL of soaking solution that fails the initial inspection with a pipette and inject it into a clean test tube.

2. Reagent reactionAdd 5 drops of industrial alkali test solution to the test tube, gently shake the tube, and observe changes in the solution and tube wall.

3. final judgment：

1. No bubble generation (no bubble attachment on the test tube wall): It is determined to contain industrial alkali and belongs to illegal added products;

2. Obvious bubbles appear: indicating that the sample contains baking soda or baking soda, not industrial alkali. It is necessary to determine whether it is added in compliance with the product label.

4、 Key precautions

• PH test strips should be sealed and stored in a cool and dry place to avoid moisture and exposure to sunlight that may cause them to fail. Before use, check the shelf life; There may be differences in the color palette of different batches of test strips, and it is necessary to compare the color palettes of the corresponding batches.

• When sampling, representative samples should be selected. If it is a batch of products, samples should be randomly taken from different packaging or different parts, mixed and tested to avoid missing detection.

• Industrial alkali testing solution should be stored away from light, and the dropper should be kept vertical during dripping to ensure uniform volume of each drop of reagent; If the test solution shows discoloration or turbidity, it is prohibited to use.

• When determining bubbles, it is necessary to observe them against a white background to avoid light interference; If samples containing industrial alkali are detected, they should be immediately sealed and sent to the laboratory for quantitative testing, and reported to relevant regulatory authorities.