Orthogonal optimization of beef stir-fried process followed by isolation and identification of the umami peptides by consecutive chromatography and LC-Q-TOF/MS

Beef is popular meat, rich in protein and delicious taste. Good stir-fried conditions could make the beef more nutritious and delicious. In this work, the optimization of stir-fried condition was studied through orthogonal method. Separation procedures utilizing ultrafiltration, Sephadex G-15 and reversed-phase high-performance liquid chromatography were used to isolate umami taste peptides. The range analysis of orthogonal methods indicated that the stir-fried time was the main factor in the taste efficiency of sensory evaluation, followed by sucrose, oil, and finally was the salt. Combined with sensory evaluation and LC-Q-TOF/MS, the amino acid sequences of five oligopeptides were identified in optimized stir-fried beef, included VAPEEHPT, LAPSTM, PECGLVVG, FADNVFAL, FAGDDAPR. There were 4 eight-peptide and 1 six-peptide. The 15 amino acids were identified in these five peptides. In the five peptides, the Pro appeared 5 times, Val and Ala appeared 4 times, Glu, Leu, Gly, Phe, and Asp appeared 3 times. The amino acid residues of Glu-Glu (EE)-continuous and Asp-Asp (DD)-continuous in the polypeptide of stir-fried beef were identified. Double umami amino acid-continuous could be important for the umami taste of peptide.