Analysis of meaty aroma and umami taste in thermally treated yeast extract by means of sensory-guided screening

YE (yeast extract) has been widely used in the flavor industry as the source to produce the high-quality meaty and umami flavors. It is because YE is rich in the savory and mellow constituents and is important precursors to generate aromas via thermal treatment. This study aims to investigate the change of meaty aroma and umami taste in the hydrolyzed YE during the thermal treatment. In this study, gas chromatography–olfactometry-mass spectrometer (GC-O-MS) was employed to detect the aroma-active compounds, and systematic approaches was used for the taste-active umami proteolytics separation and detection. The reaction conditions of two optimal samples, YE-A and YE-B, were as follows: the reaction time (A) was 90 min, the reaction temperature (B) was at 115 °C, the concentration of YE solution (C) was 0.4 g/mL, and pH (D) was 5.5 and 6.0, respectively. The GC-O-MS results show YE-A contains 31 and YE-B contains 29 key aroma-active compounds, and the priorities of four factors are both C > B > D > A. The key aroma-active compounds that contributed to meaty flavor were both 3-(methylthio)propanal (cooked potato-like), dihydro-5-pentyl-2(3H)-furanone (coconut-like, peach-like), 2-ethyl-3,5-dimethyl pyrazine (potato-like) etc . with OAVs greater than 1. The Q-TOF–MS/MS results show that YE-A contained five umami peptides, which were Ala-Asp-Ala, Pro-Gly-Asp, Glu-Met-His, Gln-Pro-Ser and Val-Glu-His; whereas YE-B contained four umami peptides, which were Glu-Asp, Pro-Ser-Gly, Ala-Glu-Ala, and Gly-Gly-Pro-Gly.