BS EN ISO 6647-2:2020 pdf – Rice – Determination of amylose content Part 2: Spectrophotometric routine method without defatting procedure and with calibration from rice standards.
1 Scope This document specifies two simplified routine methods for the determination of the amylose mass fraction of milled rice, non-parboiled. The main difference between the two methods is the dispersion procedure: method A specifies hot dispersion, and method B specifies cold dispersion. Both methods are applicable to rice with an amylose mass fraction higher than 5 %. NOTE These methods describe simplified procedures for the preparation of samples, which are frequently used in routine laboratories. The methods use the same reagents as the reference method (see ISO 6647-1), but omit the defatting step. Rice samples where the amylose mass fraction has been determined by the reference method are used as standards. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 712, Cereals and cereal products — Determination of moisture content — Reference method ISO 6647-1:2020, Rice — Determination of Amylose content — Reference method — Part 1: Spectrophotometric method with a defatting procedure by methanol and with calibration solutions of potato amylose and waxy rice amylopectin ISO 7301, Rice — Specification ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of performance characteristics — Part 1: Statistical evaluation of the linear calibration function 3? Terms? and? definitions For the purposes of this document, the terms and definitions given in ISO 6647-1 and ISO 7301 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .iso .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/
5 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. 5.1 Ethanol, a volume fraction of 95 %. 5.2 Sodium hydroxide: a) 1 mol/l solution, for method A. b) 2 mol/l solution, for method B. 5.3 Sodium hydroxide for blank solution: a) 0,09 mol/l solution, for method A. b) 0,18 mol/l solution, for method B. 5.4 Acetic acid, 1 mol/l solution. 5.5 Iodine solution. Weigh (6.8), to the nearest 5 mg, 2,000 g of potassium iodide in a weighing bottle fitted with a stopper. Add sufficient water to form a saturated solution. Add 0,200 g of iodine, weighed to the nearest 1 mg. When all the iodine has dissolved, transfer the solution quantitatively to a 100 ml volumetric flask (6.4), make up to volume with water and mix. Prepare a fresh solution on each day of use and protect it from light. 6 Apparatus Usual laboratory apparatus and, in particular, the following. 6.1 Grinder, capable of reducing uncooked milled rice to flour that will pass through a 150 µm to 180 µm (100 mesh to 80 mesh) sieve. A cyclone mill with 0,5 mm screen is recommended. 6.2 Sieve, size 150 µm to 180 µm (100 mesh to 80 mesh). 6.3 Spectrophotometer, with matching cells, usually of path length 1 cm, capable of measuring absorbance at 720 nm (or 620 nm or 680 nm). 6.4? Volumetric? flasks, 100 ml. 6.5 Boiling water bath, for method A only 6.6 Magnetic stirrer, capable of stirring at 950 r/min to 1 000 r/min, for method B only. 6.7? Conical? flasks, 100 ml.
7 Sampling A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this document. A recommended sampling method is given in ISO 24333. 8 Procedure 8.1 Determination of moisture On a separate portion of the laboratory sample and the standard samples, carry out a moisture determination in accordance with ISO 712. 8.2 Preparation of test sample In the grinder (6.1), grind at least 4 g of milled rice that will pass through the sieve (6.2). 8.3 Test portion and preparation of the test solution 8.3.1 Weigh (6.8) 100 mg ± 0,5 mg of the test sample (see 8.2) into a 100 ml conical flask (6.7). To this test portion, carefully add 1 ml of ethanol (5.1) using a pipette, washing down any of the test portion adhering to the side of the flask. Shake slightly in order to wet the entire sample. 8.3.2 Method A Pipette (6.9) 9,0 ml of sodium hydroxide solution [5.2 a)] into the conical flask and mix. Then heat the mixture on a boiling water bath (6.5) for 10 min to disperse the starch. Allow to cool to room temperature and transfer quantitatively to a 100 ml volumetric flask (6.4). Make up to volume with water and mix vigorously.