Protein fraction distribution in milling and screened physical fractions of grain amaranth
Búcaro Segura, Mía.Ester.; Bressani, R.
Archivos Latinoamericanos de Nutricion 52(2): 167-171
2002
ISSN/ISBN: 0004-0622 PMID: 12184151 Document Number: 541570
The purpose of this study was to establish protein distribution in amaranth flour based on the solubility of its fractions, specifically the flour from the germ and from the perisperm. Protein distribution was obtained by applying a series of solvents. Amaranthus cruentus samples (2000 g) were divided into 4 sub-samples, each weighing 500 g. The samples were ground, but one was left as the control. Each of the samples was screened through 18, 20, 30 and 40 mesh screens, so that 5 fractions were obtained from each of the whole grain flours. Samples of each screened fractions were observed by stereoscopy and analysed for moisture, fat and protein. This characterization suggested that the fraction above the 30 mesh screen and the flour which passed through the 40 mesh screen are probably the perisperm and germ, respectively. The 30 mesh sample contained 2.34% fat and 9.05% protein. The extraction and partitioning of the proteins indicated that the most important fractions in the germ and perisperm were the water solubles and glutelins. The relationship of the water solubles+globulin to glutelin ratio was 2.1 to 1.0 in the whole grain, 1.9-1.0 in the perisperm and 1.7-1.0 in the germ. The distribution of proteins was very similar between the germ and perisperm. The levels of prolamines were quite low. The protein extraction of the perisperm proteins retained on the 30 mesh screen was low (71.1%, by the Kjeldahl method) and 47.4% (by the Bradford method).