ISO 4134-2021 pdf free download – Meat and meat products — Determination of L-(+)-glutamic acid content — Reference method.
7.1.3 Solution R1, triethanolamine phosphate buffer solution, pH = 8,6.
Dissolve 1,86 g of triethanolamine hydrochloride in approximately 25 ml of water, adjust the pH to 8,6with 2 mol/l potassium hydroxide solution(7.1.2), detecting with a pH-meter.Add 0,68 g of octylphenoldecaethyleneglycol ether(e.g.Triton X-100). Dilute to 100 ml with water and mix (solution A).
Dissolve 0,86 g of dipotassium hydrogen phosphate (KHPO4) and 7 mg of potassium dihydrogenphosphate (KH-PO4) in water. Dilute to 100 ml with water and mix evenly (solution B).
Mix 20 ml of solution A with 5 ml of solution B.
The solution is stable for two months when stored at a temperature of between 0 °Cand 6 °C.
7.1.4 Solution R2, the mixed solution of NAD and diaphorase (lipoamide dehydrogenase EC1)1.8.1.4), PNAD = 11 mg/ml, diaphorase, approximately 4 lU/ml.
Weigh 110 mg of NAD, and approximately 8 mg (approximately 40 lU) of diaphorase into a stopperedflask.Add 10,0 ml water and mix evenly.
The solution is stable for one week when stored in the dark at a temperature of between 0 °C and 6 °c.7.1.5 Solution R3,iodonitrotetrazolium chloride (INT) solution，2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyltetrazolium chloride, p = 0,6 mg/ml.
Weigh 6 mg of INT into a small, stoppered brown flask.Add 10 ml of water and mix evenly.
The solution is stable for four weeks when stored in the dark at a temperature of between 0 °C and 6 °C.7.1.6Solution R123, the mixed solution of solution R1, solution R2 and solution R3.
Pipette 6 ml of solution R1, 2 ml of solution R2 and 2 ml of solution R3 into a stoppered brown glassbottle, and mix evenly before the test.
The mixed solution is stable for 1 h in stoppered brown glass bottles at room temperature.7.1.7 Glutamate dehydrogenase(GLDH) solution (EC1 1.4.1.3), approximately 900 lU/ml.
Weigh 10 mg (approximately 900 lU) of lyophilized glutamate dehydrogenase (GLDH) into a smallstoppered flask.Add 1 ml water and mix.
Insulated from ammonium sulfate, ethylene-dinitrilotetraacetic acid(EDTA) and glutaminase, thissolution is stable for 12 months when stored at a temperature between 0°C and 6 C.
7.1.8L-(+)-glutamic acid standard stock solution, p = 1 000 mg/l.
Weigh, to the nearest 0,000 1 g, approximately 50,0 mg of L-(+)-glutamic acid (C.H,0AN). Dissolve it inapproximately 25 ml of water.
Adjust the pH to a value range from 5 to 6 with a few drops of 2 mol/l potassium hydroxide solution(7.1.2).Then adjust the pH to 7,0 slowly with 0,02 mol/l potassium hydroxide solution(7.1.2). Dilute to5o ml with water and mix evenly.
The solution is stable for six months when stored at a temperature between 0 °Cand 6 °c.
7.1.9 L-(+)-glutamic acid standard solution, p = 100 mg/l.
Pipette accurately 5,0 ml of L-(+)-glutamic acid standard stock solution (7.1.8) into a 50 ml volumetricflask (7.2.8), dilute to the mark with water and mix evenly.
The solution is for the current use.
7.1.10 L-(+)-glutamic acid series standard solution, p = 5 mg/1,10 mg/1,15 mg/1,20 mg/l,30 mg/1and 40 mg/l.
Pipette accurately 0,50 ml, 1,00 ml, 1,50 ml, 2,00 ml, 3,00 ml and 4,00 ml ofL-(+)-glutamic acid standardsolution (7.1.9) into each of six 10 ml volumetric flasks (7.2.8〕 separately, dilute to the mark with waterand mix evenly.
The solution is for the current use.7.2Apparatus
The usual laboratory equipment and, in particular, the following shall be used.
7.2.1 Mechanical or electrical equipment, capable of homogenizing the laboratory sample.
This includes a high-speed rotational cutter,or a mincer fitted with a plate with apertures not exceeding4,0 mm in diameter.
7.2.2 Laboratory mixer, a stirrer or an oscillator.
7.2.3 Laboratory centrifuge, with 50 ml or 100 ml centrifuge tubes, operating at a radial accelerationof about 2 000g or an equivalent speed (e.g. 3 500 r /min to 4 000 r/min).
7.2.4Analytical balance, capable of weighing to the nearest 0,001 g, 0,000 1 g.
7.2.5 Constant temperature drying box.
7.2.6pH-meter.
7.2.7 Filter papers, with a diameter of about 15 cm, high or moderate speed.ISO 4134 pdf download.