Effects of Different Drying Methods on Quality Attributes and Volatile Flavor Compounds of Pleurotus geesteranus Extracts

To investigate the effects of different drying methods on physicochemical properties, flavor components, and volatile compounds in Pleurotus geesteranus extracts, three drying techniques were employed: vacuum freeze drying (VFD), microwave vacuum drying (MVD), and spray drying (SD). The moisture content, protein concentration, crude polysaccharide content, pH, color parameters, amino acid composition, peptide molecular mass distribution, volatile compounds, and γ-glutamyl peptides of the extracts were determined. Results indicated that different drying methods significantly influenced various quality indicators of P. geesteranus extracts (P < 0.05). Compared with the other methods, SD resulted in significantly higher moisture content (9.03 g/100 g) and color parameters (L value 58.68, a value 10.91, and b value 24.64). In terms of flavor-active constituents, the total content of free amino acids (16.78 mg/100 g) and the proportion of peptides with molecular masses less than 180 Da (59.68%) were significantly higher in the SD samples than in the other dried samples (P < 0.05). Electronic tongue analysis combined with principal component analysis (PCA) revealed that MVD exhibited superior umami, bitterness, bitter aftertaste and richness intensities relative to the other methods (P < 0.05). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) identified 17 γ-glutamyl peptides across all samples, among which 10 were common to these samples. The VFD samples showed the highest peptide abundance (8.74 × 10⁸), whereas MVD samples retained the greatest number of peptides (16). A total of 34 volatile compounds were detected across the three dried samples, with 13 pyrazines and 9 alcohols being the primary contributors to aroma formation. The VFD samples exhibited the greatest number of volatile compounds and the best retention of mushroom aroma. These findings provide valuable insights for optimizing the deep processing of P. geesteranus and guiding the development of high-value functional products.