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ISO 9648:1988 pdf free

ISO 9648:1988 pdf free.Sorghum – Determination of tannin content
ISO 9648 specifies a universal method for the determination of tannin content in sorghum grains.
It is not specific for one single type of polyphenols. Its usefulness, meanwthile, is justified by the good negative cor-relation observed between the metabolizable energy of sorghum grain, measured using animal experiments on cocks, and the results obtained using this method.
The following standards contain provisions which, through reference in this text, constitute provisions of ISO 9648. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on ISO 9648 are encour-aged to investigate the possibility of applying the most recent editions of the standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 712 : 1985, Cereals and cereals products – Determination of moisture content (Routine reference method).
ISO 950: 1979, Cereals – Sampling (as grain).
Extraction of tannins by shaking with dimethylformamide.
After centrifuging, addition of ferric ammonium citrate and am-monia to an aliquot part of the supernatant liquid and spec-trometric determination, at 525 nm, of the absorbance of the solution thus obtained. Determination of the tannin content using a calibration curve prepared using tannic acid.
Determine the calibration curve on the day of the determination as indicated in a) to c).
a) Prepare six 20 ml volumetric flasks (5.11) and, using a graduated pipette (5.9), add to them respectively 0 ml, 1 ml, 2 ml, 3 ml, 4 ml and 5 ml of the tannic acid solution (4.1).
Make up to the mark with the dimethylformamide solution (4.3). The calibration scale thus obtained corresponds to tannic acid contents of 0 mg/ml, 0,1 mg/ml, 0,2 mg/ml, 0,3 mg/ml, 0,4 mg/ml and 0,5 mg/ml respectively.
b) Pipette into test tubes (5. 10) 1 ml of each of these sol-utions and add successively, using a pipette (5.8), 5 ml of water and 1 ml of the ferric ammonium citrate solution (4.4), and shake for a few seconds using the shaker (5.6).Then add 1 ml of ammonia solution (4.2) and shake again for a few seconds using the shaker (5.6).
Transfer the solutions thus obtained into measuring cells and after 10 min±1 min measure the absorbances, at 525 nm, using the spectrometer against a water blank.
c) Plot the calibration curve, using the absorbance values as the ordinate and the corresponding concentrations of tannic acid on the calibration scale [a)] as the abscissa, in milligrarms per millilitre.
The curve should not pass through the origin and shall not be corrected for the zero of the scale.ISO 9648 pdf download.

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