engleski

Free amino group distribution between barley albumin and globulin protein and non-protein fractions

Free amino group determination in extracts of various cereal flours or doughs has been widely used for estimation of albumins/globulins and/or glutenins amino group loss caused by non-enzymatic glycosylation or transglutaminase protein cross-linking. However, distribution of free amino groups between albumins and globulins, as well as small peptides and free amino acids present in such extracts, is less studied. Therefore, the aim of this study was to determine contribution of albumins, globulins, small peptides and free amino acids present in barley extracts in detection of free amino group content. Albumins, globulins or albumin/globulin protein extracts of six barley varieties, as well as their corresponding non-protein TCA-soluble fractions, were examined for protein and free amino group content. Results showed that the majority of free amino groups present in barley albumins, globulins or albumins/globulins extracts originate from their non-protein TCA-soluble fractions as follows: 83-89% for albumins, 39-76% for globulins, and 60-84% for albumins/globulins. Free amino groups were found to be 2 to 4 times greater in albumin extracts and their corresponding TCA-soluble fractions than in globulin extracts. Observed data clearly suggest that when dealing with free amino group determination in barley flour extracts special attention should be given to the contribution of non-protein TCA soluble fractions.

albumins; barley; free amino groups; globulins; small peptides

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