Flavor composition and enzyme-associated volatile changes during hot-air and vacuum drying of Stropharia rugosoannulata

Stropharia rugosoannulata is a highly perishable edible mushroom, but the effects of drying on its flavor-related composition and enzyme-associated volatile changes remain unclear. This study compared hot-air drying (HAD) and vacuum drying (VD) at 50, 60, and 70 °C by monitoring free amino acids (FAA), organic acids, 5′-nucleotides, volatile compounds, lipoxygenase (LOX) activity, and alcohol dehydrogenase (ADH) activity at different drying stages. Drying markedly altered both volatile and non-volatile components. At the end of drying, HAD60 showed higher FAA, organic acid, and 5′-nucleotide contents (49.31, 178.63, and 5.24 mg/g dry weight, respectively) than VD60 (36.42, 137.44, and 4.14 mg/g dry weight). The estimated total volatile content was also higher under HAD60 than VD60. LOX activity peaked in HAD60 at D-2 (2479.99 U/g), whereas ADH activity peaked in HAD50 at D-3 (1.81 U/g), and both activities subsequently declined. HAD at 50–60 °C was associated with higher abundances of several measured volatiles, including oct-1-en-3-ol, 3-methylbutanal, hexanal, and benzaldehyde. Overall, among the conditions evaluated, HAD60 showed a comparatively favorable profile of the measured flavor-related components, while the stage-dependent changes in LOX and ADH activities were associated with shifts in volatile composition.