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1、INTERNATIONAL STANDARD IS0 11052 First edition 1994-09-01 Durum wheat flour and semolina - Determination of yellow pigment content Farines et semoules de b/6 dur - D - easy to clean; - of minimal dead space; - capable of grinding rapidly and uniformly without heating, and avoiding as far as possible
2、 contact of the sample with the outside air. 6.2 Spectrometer, capable of operating at a wave- length of 440 nm. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 01:36:10 MDTNo
3、reproduction or networking permitted without license from IHS -,-,- IS0 11052:1994(E) 0 IS0 6.3 Erlenmeyer flasks, of capacity 200 ml, prefera- bly of brown glass, with ground glass stoppers. 6.4 Erlenmeyer flasks, of capacity 100 ml. 6.5 Volumetric flasks, of capacity 10 ml, narrow- necked, with gr
4、ound glass stoppers. 6.6 Volumetric flasks, of capacities 100 ml and 250 ml, with ground glass stoppers. 6.7 Pipettes, of capacities 20 ml and 25 ml. 6.8 Watch glass or Petri dish, as cover for the funnel (6.10). water-saturated n-butanol (5.1) to give a homogene- ous suspension. Shake gently in the
5、 stoppered flask several times during the first hour. Allow the suspen- sion to stand overnight (16 h to 18 h) at room tem- perature. NOTE 2 If no brown glass flasks are available, protect the stoppered flask from light. The next morning, shake the contents again, the ter completely through the flut
6、ed filter paper into a 100 ml Erlenmeyer flask (6.4). To avoid sol loss by evaporation, place the funnel (6.10) on flask and cover it with a watch glass or Petri (6.8). 10.2 Determination 6.9 Filter paper, hard, fluted. 6.10 Funnel. 6.11 Analytical balance, capable of weighing to an accuracy of 0,00
7、1 g. 7 Sampling It is important that the laboratory receive a sample which is truly representative and has not been dam- aged or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in IS0 2170. 8 Pre
8、paration of test sample NOTE 1 A comparative study has demonstrated particle size under 0,5 mm is appropriate. that a 9 Determination of moisture content Determine the moisture content of the test sample in accordance with IS0 712. 10 Determination of yellow pigment 10.1 Preparation of extract In a
9、200 ml Erlenmeyer flask (6.3), weigh, to the nearest 0,001 g, 10 g of the test sample, ground if necessary (see clause 8). Disperse it in 50 ml of n fil- 6.9) vent the dish Measure the optical density of the clear filtrate at 440 nm as absorbance, using the spectrometer (6.2). Use unfiltered water-s
10、aturated n-butanol for setting-up the instrument and for the blank determi- nations. Read the corresponding p-carotene content from the calibration curve (I 0.4). 10.3 Preparation of standard solution of /I-carotene In a 100 ml one-mark volumetric flask (6.6), weigh, to within 0,001 g, exactly 0,025
11、 g of p-carotene. Dis- solve it in diethyl ether (5.2). Make up to the mark with diethyl ether and mix carefully. Take, using a pipette (6.7), 20 ml of this homogeneous solution ( = 5 mg of b-carotene) and place in a 250 ml one- mark volumetric flask (6.6). Make up to the mark with water-saturated n
12、-butanol (5. I ) and mix carefully. Then take, using the pipette, 25 ml of this solution and place in a 100 ml one-mark volumetric flask (6.6). Make up to the mark with the water-saturated nbutanol and mix carefully. This is the standard sol concentration: ution. It has the following 1 ml = 0,005 mg
13、 = 5 gg B-carotene. 10.4 Preparation of calibration curve Prepare suitable dilutions of the standard solution (10.3) with water-saturated n-butanol in calibrated 10 ml volumetric flasks (6.5) (e.g. from 0,5 ml to 3 ml of standard solution in 10 ml). Measure the absorbance A, of each dilution and es-
14、 tablish a calibration curve (/?-carotene in 10 ml of sol- ution as a function of absorbance). 2 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 01:36:10 MDTNo reproduction or ne
15、tworking permitted without license from IHS -,-,- 0 IS0 IS0 11052:1994(E) 11 Calculation The yellow pigment content, wp, expressed as milli- grams of b-carotene in 100 g of dry matter, is equal to wp = 5a 100-H where a is the b-carotene content corresponding to the 10 ml extract (equivalent to 2 g o
16、f the test sample), in milligrams; H is the moisture content of the test sample, expressed as a percentage by mass. 12 Precision Results of an interlaboratory test are given in annex A. ference between two single test results, obtained using the same method on identical test material in the same lab
17、oratory by the same operator using the same equipment within a short interval of time, should not be greater than 0,03 mg/lOO g. 12.3 Reproducibility For a yellow pigment content within the range of 0,651 mg/lOO g to 0,754 mg/lOO g, the absolute dif- ference between two single test results, obtained
18、 using the same method on identical test material in different laboratories with different operators using different equipment, should not be greater than 0,3 mg/lOO g. 13 Test report The test report shall specify - the method in accordance with which sampling was carried out, if known, 12.1 Accurac
19、y - the method used, Since B-carotene is used for calibration but is not present, or is only a minor constituent of the grain endosperm pigments, the resulting values may devi- ate by up to 5 % from the true value. However, as xanthophyl (lutein) is not readily available for cali- bration, this erro
20、r is unavoidable and is of minor con- sequence. 12.2 Repeatability For a yellow pigment content within the range of 0,651 mg/lOO g to 0,754 mg/lOO g, the absolute dif- - the test result(s) obtained, and - if the repeatability has been checked, the final quoted result obtained. It shall also mention
21、all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the test result(s). The test report shall include al for the complete identification I informatio of the sam n necessary Pie . 3 Copyright Int
22、ernational Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 01:36:10 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 11052:1994(E) Annex A (informative) Results of interlabo
23、ratory test An interlaboratory test, carried out by the International of which carried out four determinations on each Association for Cereal Science and Technology (ICC) sample, gave the statistical results (evaluated in ac- in 1989, in which seven laboratories participated, each cordance with IS0
24、5725) shown in tableA.l. Table A.1 Sample I II III IV V VI Number of laboratories retained after . eliminating outliers 7 7 7 7 7 7 Mean content, mg/lOO d.m.1) g 0,754 0,731 0,697 0,699 0,658 0,651 Standard deviation of repeatability &., mg/lOO g d.m. 0,007 28 0,007 21 0,010 8 0,005 68 0,006 05 0,00
25、7 36 Coefficient of variation of repeatability, % 0,96 0,99 I,55 0,81 0,92 I,13 Repeatability, 2,83 $, mg/lOO g d.m. 0,020 0,020 0,031 0,016 0,017 0,021 Standard deviation of reproducibility, Sr, mg/lOO g d.m. 0,082 0 0,084 3 0,096 5 0,098 6 0,105 6 0,088 0 Coefficient of variation of reproducibilit
26、y, % IO,83 II,53 13,84 14,24 16,05 13,52 Reproducibility, 2,83 &., mg/lOO g d.m. 0,233 0,238 0,273 0,282 0,299 0,249 1) d.m. = dry matter 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 0
27、4/26/2007 01:36:10 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 11052:1994(E) Annex B (informative) Bibliography I IS0 2170: 1980, Cereals and pulses - Sampling of milled products. 2 IS0 5725:1986, Precision of test methods - Determination of repeatability and reprod
28、ucibility for a standard test method by inter-laboratory tests. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 01:36:10 MDTNo reproduction or networking permitted without licens
29、e from IHS -,-,- IS0 11052:1994(E) KS 67.060.00 Descriptors: agncultural products, plant products, food products, cereal products, durum wheat, flours (food), semolina, tests, determination, pigments, comparative tests. Price based on 5 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 01:36:10 MDTNo reproduction or networking permitted without license from IHS -,-,-
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