Determining the Amino Acid Composition of Soybean Proteins Using IR Scanners

Sergey Nizkii, Galina Kodirova, Galina Kubankova


The amino acid composition of plant-based proteins consists of twenty individual amino acids and is expressed as the ratio of each of them to the sum of all (expressed as percentage). Sixteen of twenty amino acids included in the composition of plant-based proteins are most effectively determined on the liquid chromatographers. The technology of high-performance liquid chromatography is to a certain extent costly both in time and in sample preparation, which makes this method unsuitable for mass analysis; for example, for evaluating a breeding material. In this case, the suggested method based on scanning in the near infrared radiation band is more efficient. Despite the fact, that IR-scanners are able to determine a sufficiently large number of components on the basis of one calibration equation, a constant correction is required when it is needed to determine the composition of amino acids and reduce it to a percentage ratio. The options for creating calibration equations (models) for determining the amino acid composition of soybean proteins for computer programs (Nir 42, ISI) which provide the operation of IR-scanners, such as NIR-4250 or FOSS NIRSistem 5000 (FOSS Analytical A/S, Denmark) are considered in the article. It was found that when creating calibration equations, it is most correct to set for each amino acid its mass content (g per 100 g of protein), and not the relative portion (in %), as it has also been done in other methods described in the literature.

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