Nutritional characterization of millet protein concentrates produced by a heat-stable alpha-amylase digestion

We prepared various millet protein concentrates by a heat-stable alpha-amyl ase (Termamyl 120L) digestion, i.e., foxtail millet (FC), prose millet(PC), Japanese white barnyard millet (WBC) and Japanese black barnyard millet pr otein concentrates (BBC). Nutritional characterization for these protein co ncentrates was performed from the aspects of chemical and protein compositi ons, amino acid composition, and protein digestibility, biological value an d net protein utilization were determined using rats. The yield of millet p rotein concentrates was 10% or more, and the protein recovery of millet pro tein concentrates exceeded 85% irrespective to the original millet flours. Protein concentrations of FC, PC, WBC and BBC were 668, 777, 763 and 637 g. kg(-1), respectively. The lower protein concentration of BBC would reflect the higher dietary fiber content in the original millet flour, because diet ary fiber fraction was concentrated in the process of protein production. A lthough lysine contents of millet protein concentrates were slightly lower than those of the corresponding millet flours, protein compositions of mill et protein concentrates were similar to those of the corresponding millet f lours. Lysine was the first limiting amino acid for all millet protein conc entrates. The amino acid score of FC (28) was higher than those of PC (21), WBC (23) and BBC (25), and protein digestibility of FC (90%) was also high er than those of PC (80%), WBC (71%) and BBC (61%). The net protein utiliza tion of FC (37%) was slightly higher than those of PC (35%), WBC (32%) and BBC(33%). Repeated production of millet protein concentrates confirmed that our method using a heat-stable alpha-amylase would be suitable for an indu strial mass-production,and that the resultant millet protein concentrates w ould be useful enough to sustain a protein nutrition in combination with ot her foods. FC, in particular, would be the most recommendable millet protei n concentrate among all millet protein concentrates tested. (C) 1999 Elsevi er Science Inc.