In order to explore the flavor composition profiles of fresh and dried Stropharia rugosoannulata and the key components determining its good flavor, the aroma and flavor components of fresh and dried samples prepared by four different drying methods, namely hot air drying (HAD), vacuum freeze drying (VFD), microwave drying (MWD), natural drying (ND) were analyzed. A total of 118 aroma compounds were detected. After drying, the aroma richness was significantly improved (P < 0.05), and VFD could retain the aroma quality of fresh mushroom to a large extent. Meanwhile, 19 aroma components common to all samples were found to constitute the characteristic component profile of S. rugosoannulata, among which the number and content of aldehydes were dominant, especially for n-hexanal (green aroma). The total amounts of soluble sugar and free amino acids in the HAD sample were significantly higher than those in the fresh sample, and the loss of flavor nucleotides in the VFD sample was least. Therefore, the two drying methods had significant advantages in equivalent umami concentration (EUC) (P < 0.05). The comprehensive sensory score for flavor was in the decreasing order of VFD > HAD > ND > fresh sample > MWD. A partial least squares regression model was established based on the sensory scores and the component data. The R_X², R_Y² and Q² of the first three principal components were 79.4%, 98.9%, and 0.974, respectively. The loading information showed that the interaction between aroma and taste characteristics was obvious. Variable importance in projection scores showed that sweet amino acids, 1-octene-3-ol, butyl-2-octenal and EUC were crucial for the good characteristic flavor of S. rugosoannulata. This study will provide a theoretical basis for subsequent screening of sample pretreatment methods and the development of flavor related products.

Umami peptides from the enzymatic hydrolysate of Stropharia rugosoannulata were separated by ultrafiltration (UF) and gel filtration chromatography (GFC) combined with sensory evaluation and electronic tongue analysis. Fraction F3, with the strongest umami intensity, were identified by reversed-phase high performance liquid chromatography-tandem mass spectrometry (RP-HPLC-MS/MS). The identified peptides were synthesized and evaluated for their taste characteristics. The results showed that eight umami peptides were identified in fraction F3, namely ELWR, RLVDR, KPDNR, AHLRF, LDWDR, LAEWR, DDWWR and EGHKGW, and all of them possessed umami characteristics and umami-enhancing effects with thresholds ranging from 0.30 to 1.33 mmol/L and from 0.53 to 2.43 mmol/L, respectively. All peptides except LDWDR showed different degrees of umami improvement in monosodium glutamate (MSG) solution, ranging from 0.18% to 61.12%. ELWR, RLVDR, KPDNR, AHLRF and EGHKGW showed good umami-enhancing effects at low concentrations. The peak concentration of RLVDR and KPDNR for synergistic umami-enhancing effect was 5 mg/mL. LDWDR, LAEWR, DDWWR and EGHKGW reached the umami peak at 4 mg/mL. The amino acid composition and the spatial structure of umami peptides could affect their taste properties. The results of this study provide a theoretical basis for the development and utilization of umami peptides from S. rugosoannulata.