pH Meter Determination of pH Test Standards for Meat and Meat Products
1 Subject content and scope of application
This standard specifies the pH determination method for meat and meat products.
This standard applies to the pH determination of meat and meat products.
2 Reference standards
GB 9695.19 Meat and Meat Products Sampling Methods
3 principle
Determination of the potential difference between a glass electrode immersed in a sample of meat and meat products and a reference electrode.
4 Reagents
4.1 95% ethanol (GB 679).
4.2 Diethyl ether (HG 3-1002): saturated with water.
4.3 Distilled water, or water of equivalent purity.
5 Instruments and equipment
5.1 pH meter: the accuracy is 0.05pH unit. The instrument should have a temperature compensation system and be able to prevent the influence of external induced current.
5.2 Glass electrodes: Glass electrodes of various shapes can be used. The membrane of the glass electrode should be preserved in water.
5.3 Reference electrode: such as calomel electrode or silver chloride electrode containing saturated potassium chloride solution. It is generally preserved in a saturated potassium chloride solution.
Note: The reference electrode and glass electrode can also be assembled into a composite electrode, which is generally preserved by immersing it in distilled water.
5.4 Meat grinder: the hole diameter shall not exceed 4mm.
6 Sample
6.1 Sampling according to GB 9695.19.
6.2 Take at least 200g of a representative sample and measure the pH immediately, or store the sample in an appropriate way to ensure that the pH change is controlled within a minimum limit.
7. Analysis steps for homogenized samples
7.1 Preparation of samples
The sample must pass through the meat grinder twice to achieve homogenization.
If the sample is very dry, it can be homogenized by adding equal quality water to the laboratory mixer.
7.2 Calibration of pH meter
Use a buffer solution of known pH value (as close as possible to the pH value of the solution to be tested. See Appendix A), and calibrate the pH meter at the measurement temperature.
7.3 Determination
Take a certain amount of sample enough to immerse or embed the electrode, insert the electrode into the sample, and use the steps suitable for the pH meter used for measurement. Three determinations are made on the same sample and the readings are to the nearest 0.05 pH units.
7.4 Electrode cleaning
Use absorbent cotton to wipe the electrode with ether and ethanol successively, and finally rinse with water and save the electrode.
7.5 Calculation of analysis results The difference between three measurement results carried out simultaneously or successively by the same analyst shall not exceed 0.15pH units. Calculate
When the analysis results meet the requirements of the allowable difference, take the arithmetic mean of the three measurements as the result. to 0.1 pH units.
7.6 Allowable difference
8. Analysis steps of heterogeneous samples
8.1 Calibration of pH meter
8.2 Determination
Take a sample sufficient to determine the pH at several points. If the sample tissue is hard, a hole can be punched at each measurement point so that the glass electrode will not be damaged. Insert the electrode into the sample and measure using the steps appropriate to the pH meter used. Repeat the measurement at the same point. The measurement can be repeated at different points if necessary, and the number of measurement points depends on the nature and size of the sample.
8.3 Electrode cleaning
8.4 Calculation of analysis results
When the analysis results meet the requirements of the allowable difference, take the arithmetic mean of the two measured values obtained at the same point as the result. Report the average pH value at each point, to the nearest 0.1 pH unit.
8.5 Allowable difference
The difference between the two values obtained at the same point shall not exceed 0.15 pH units.
