ISO 4134:2021 pdf download – Meat and meat products — Determination of L-(+)- glutamic acid content — Reference method.
5 Sampling Sampling is not part of the method specified in this document. A recommended sampling method is given in CAC/GL 50-2004. It is important that the sample received by the laboratory is truly representative and has not been damaged or changed during transport or storage. Start from a representative sample of at least 200 g. Store the sample at a temperature of 4 °C or frozen at −18 °C if not immediately analysed, so that deterioration and change in composition are prevented. 6 Preparation of test sample Homogenize the laboratory sample with the appropriate equipment (see 7.2.1). Note that the temperature of the sample should not exceed 25 °C. If a mincer is used, process the sample at least twice with the equipment. Fill a suitable airtight container with the prepared sample. Seal the container and store it at a temperature of 4 °C or frozen at −18 °C if not immediately analysed, so that deterioration and change in composition are prevented. Analyse the sample as soon as practicable, but always within 24 h after homogenization. 7 Test method of spectrophotometer 7.1 Reagents Only reagents of recognized analytical grade and only water of at least grade 2 purity as defined in ISO 3696 shall be used. Except for the solutions of inorganic compounds (7.1.1 and 7.1.2), store all solutions in stoppered brown glass bottles which have been scrupulously cleaned and steamed or sterilized.
7.1.1 Dilute perchloric acid, c = 1,0 mol/l. WARNING — Contact with oxidizable or combustible materials or with dehydrating or reducing agents? can? result? in? fire? or? explosion.? Persons? using? this? acid? should? be? thoroughly? familiar? with? its hazards. See the safety practices listed in Annex A. Add 8,6 ml of the perchloric acid (70 g/ 100 g, ρ 20 = 1,67 g/ml) to the bulk of water, diluting to 100 ml. 7.1.2 Potassium hydroxide solution, c = 4 mol/l, 2 mol/l, 0,5 mol/l and 0,02 mol/l. Dissolve 22,4 g of potassium hydroxide in water. Dilute the solution to 100 ml, c = 4 mol/l, and mix evenly after cooling. Dissolve 11,2 g of potassium hydroxide in water. Dilute the solution to 100 ml, c = 2 mol/l, and mix evenly after cooling. Transfer 2,5 ml of 2 mol/l potassium hydroxide solution to 10 ml volumetric flask, dilute to the mark with water and mix, c = 0,5 mol/l. Transfer 0,1 ml of 2 mol/l potassium hydroxide solution to 10 ml volumetric flask, dilute to the mark with water and mix, c = 0,02 mol/l.