Difference in Volatile Aroma Components of Stropharia rugosoannulata under Two Cultivated Environments Investigated by SPME-GC-MS

Abstract

In order to study the effect of both greenhouse and forest cultivating environments on Stropharia rugosoannulata, its volatile aroma compounds were measured by a headspace solid phase micro extractions—gas chromatograph—mass spectrometer (SPME–GC–MS). The optimal adsorption temperature was 75 °C and the optimal adsorption time was 40 min. A total of 36 volatile aroma compounds were identified by GC–MS, including 8 aldehydes, 2 ketones, 4 alcohols, 15 alkenes, and 4 alkanes. Hexanal, 3-Octanone, 2-Undecanone, (E)-Nerolidol, and (Z)-β-Farnesene made great aromatic contributions. Among them, Hexanal, 3-Octanone, 2-Undecanone were the key aroma compounds for which odor activity values (OAVs) were more than 1. (E)-Nerolidol showed odor modification in the forest samples and showed a key aroma effect in greenhouse samples. (Z)-β-Farnesene showed odor modification in greenhouse samples. 3-Octanone was the largest contributing compound for which the OAV was more than 60. The total content of volatile aroma compounds first increased and then decreased with growth time; it reached the highest level at 48 h: 2203.7 ± 115.2 μg/kg for the forest environment and 4516.6 ± 228.5 μg/kg for the greenhouse environment. The aroma was the most abundant at this time. All samples opened their umbrella at 84 h and become inedible. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and orthogonal partial least squares discriminant analysis (OPLS–DA) were combined to analyze the aroma difference of S. rugosoannulata under two cultivation modes. PCA and HCA could effectively distinguish the aroma difference in different growth stages. Under different culturing methods, the aroma substances and their changes were different. The samples were divided into two groups for forest cultivation, while the samples were divided into three groups for greenhouse cultivation. At the end of growth, the aroma of S. rugosoannulata with the two cultivation modes was very similar. OPLS–DA clearly distinguished the differences between the two cultivation methods; 17 key aroma difference factors with variable importance projection (VIP) > 1 were obtained from SPLS–DA analysis.