Abstract:Proteins were extracted from buckwheat, highland barley, and wheat by alkaline extraction and acid precipitation. The relative molecular weight, amino acid composition of the digests, amino acid score (AAS), chemical score (CS), and essential amino acid index (EAAI) of the three cereal proteins during gastrointestinal digestion were characterized. Meanwhile, models of STC-1 cells and ICR mice were used to evaluate the effects of the digests on intestinal glucagon-like peptide-1 (GLP-1) secretion. The results showed that after gastrointestinal digestion of buckwheat, highland barley, and wheat proteins, the relative molecular weights of the digests were all less than 10 000. The peptides with relative molecular weights less than 3 000 in buckwheat, highland barley, and wheat protein digests accounted for 72%, 98%, and 56%, respectively. The proportions of essential amino acids in the protein digests of buckwheat, highland barley, and wheat were 38.33%, 30.74%, and 35.70%, respectively, and the essential amino acid indexes were 0.85, 0.88, and 0.91, respectively. All the digests lacked sulfur-containing amino acids (Met+Cys). The three protein digests significantly promoted the GLP-1 secretion in STC-1 cells. The results of mouse experiments also showed that the three protein digests significantly promoted the secretion of GLP-1 in the enteroendocrine cells of mice, and the digests of buckwheat and highland barley proteins outperformed that of wheat protein. The above results indicated that the nutritional values of buckwheat and highland barley proteins were lower than that of wheat protein, while the digests of buckwheat and highland barley proteins were superior to that of wheat protein in promoting GLP-1 secretion in enteroendocrine cells. This suggested that buckwheat protein and highland barley protein were more suitable than wheat protein for patients with metabolic diseases such as diabetes.
