Detection of canned pork chops with five flavors

This standard specifies the analytical steps for determining sodium chloride in food using indirect precipitation titration and potentiometric titration methods; And provided the analytical steps for the direct precipitation titration method (Appendix A) to determine sodium chloride in food. The indirect precipitation titration method and direct precipitation titration method of this standard are applicable to the determination of sodium chloride in meat products, aquatic products, vegetable products, pickled foods, seasonings, and starch products, but are not applicable to the determination of sodium chloride in dark colored foods; The potentiometric titration method is suitable for the determination of sodium chloride in various foods and dark colored foods mentioned above. 2 Normative References: The clauses in the following documents become clauses of this standard through reference in this standard. For dated reference documents, all subsequent amendments (excluding corrected content) or revisions are not applicable to this standard. However, parties to agreements based on this standard are encouraged to study whether to use the latest versions of these documents. For undated references, the latest version applies to this standard. GB/T 6682 Specification and Test Methods for Analytical Laboratory Water (GB/T 6682-1992, neq ISO 36961987) 3. Indirect Precipitation Titration Method 3.1. Method Abstract: After the test solution is acidified, an excess silver nitrate solution is added, and the excess silver nitrate is titrated with potassium thiocyanate standard titration solution using ammonium iron sulfate as the indicator (Folhart method). Calculate the content of sodium chloride in food based on the consumption of potassium thiocyanate standard titration solution. 3.2 Reagents and Solutions 3.2.1 Reagents and Analytical Water: Unless otherwise specified, all reagents shall use analytical pure reagents; The analysis water should comply with the secondary water specifications specified in GB/T 6682. 3.2.2 Glacial acetic acid. 3.2.3 Protein precipitant: 3.2.3.1 Precipitator I: Weigh 106 g of potassium ferrocyanide, dissolve in water, transfer to a 1000 mL volumetric flask, and dilute with water to the mark. 3.2.3.2 Precipitator II: Weigh 220 g of zinc acetate, dissolve it in water, add 30 mL of glacial acetic acid, transfer to a 1000 mL volumetric flask, and dilute with water to the mark. 3.2.4 Nitric acid solution (1:3) Mix 1 volume of concentrated nitric acid with 3 volumes of water. Boil and cool before use. 3.2.5 Ethanol solution (80%): Mix 80 mL of 95% ethanol with 15 mL of water. Preparation of 0.1 mol/L silver nitrate standard titration solution; Weigh 17 g of silver nitrate, dissolve in water, transfer to a 1000 mL volumetric flask, dilute with water to the mark, shake well, and place in a dark place. Preparation of 0.1 mol/L potassium thiocyanate standard titration solution; Weigh 9.7 g of potassium thiocyanate, dissolve in water, transfer to a 1000 mL volumetric flask, dilute with water to the mark, and shake well. 3.2.8: Saturated solution of ammonium iron sulfate: Weigh 50 g of ammonium iron sulfate and dissolve it in 100 mL of water. If there is any precipitation, filter it. 3.2.9 Calibration of 0.1 mol/L silver nitrate standard titration solution and 0.1 mol/L potassium thiocyanate standard titration solution: 3.2.9.1 Precipitation of chloride: Weigh 0.10 g to 0.15 g of standard reagent sodium chloride (or analytical pure sodium chloride that has been burned to constant weight at 50O ℃ to 600 ℃), accurate to 0.000 2 g, dissolve in water in a 100 mL beaker, and transfer to a 100 mL volumetric flask. Add 5 mL of nitric acid solution (3.2.4), vigorously shake while adding 30.00 mL (V;) 0.1 mol/L silver nitrate standard titration solution (3.2.6), dilute with water to the mark, and shake well. Leave in a dark place for 5 minutes, filter with a quick filter paper, and discard the initial 10 mL of filtrate

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