Agricultural product quality parameters 222774 detection

This standard specifies the analytical steps for determining total acids in food using acid-base titration and pH potentiometry. This standard is applicable to the determination of total acids in fruits and vegetables, beverages, dairy products, beverage spirits, bee products, starch products, grain products, and condiments. The acid-base titration method of this standard is not applicable to colored or opaque test solutions. 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. Therefore, parties to agreements based on this standard are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest version applies to this standard. GB/T 601 Preparation of Standard Titration Solutions for Chemical Reagents GB/T 604 General Method for Determination of pH Discoloration Domain of Acid and Base Indicators GB/T 6682 Specification and Test Methods for Analytical Laboratory Water (GB/T 6682-1992, neq ISO 3696; 1987) 3 Acid and Base Titration Method 3.1 Method Summary: According to the principle of acid-base balance, titrate the acid in the test solution with alkaline solution, and determine the titration endpoint with phenolphthalein as the indicator. Calculate the total acid content in food based on the consumption of alkaline solution. 3.2 Reagents and Solutions 3.2.1 Reagents and Analytical Water All reagents are analytical pure reagents; The water used for analysis should comply with the secondary water specifications specified in GB/T 6682 or distilled water, and should be boiled and cooled before use. 3.2.20. Prepare and calibrate 1 mol/L sodium hydroxide standard titration solution according to GB/T 601. 3.2.30.01 mol/L sodium hydroxide standard titration solution Dilute 100 mL of 0.1 mol/L sodium hydroxide standard titration solution (3.2.2) to 1000 mL (diluted on the same day of use). 3.2.40.05 mol/L sodium hydroxide standard titration solution Dilute 100 mL of 0.1 mol/L sodium hydroxide standard titration solution (3.2.2) to 200 mL (diluted on the same day of use). 3.2.51% Phenolphthalein Solution Weigh 1g of phenolphthalein - dissolve in 60 mL of 95% ethanol, dilute with water to 100 mL. 3.3 Instrument and Equipment 3.3.1 Tissue Crusher. 3.3.2 Water bath pot. 3.3.3 Mortar. 3.3.4 Condensing Tube. 3.4 Preparation of samples 3.4.1 Liquid samples without carbon dioxide: Mix thoroughly and place in a closed glass container

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