Abstract: This study aimed to evaluate the quality characteristics of fresh straw mushroom (Volvariella volvacea) and straw mushroom chips produced by either low-temperature vacuum frying or vacuum freeze drying. The sensory attributes were evaluated and the contents of moisture, fat, soluble protein, polysaccharide and volatile flavor components were analyzed by chemical method and solid-phase micro-extraction combined with gas chromatography-mass spectrometry (SPME-GC-MS). Results showed that the hardness and brittleness of vacuum freeze dried chips were 5.965 kg and 1.881 mm respectively; they revealed a porous structure with large pores and their color and nutritional content were nearly identical to those of fresh straw mushroom. The nutritional content of low-temperature vacuum fried chips was significantly lower than that of fresh straw mushroom (P < 0.05) and the hardness and brittleness were 4.454 kg and 3.336 mm, respectively. They showed a loose internal structure and exhibited the typical color of fried food. In addition, the types and amounts of volatile flavor components varied between fresh straw mushroom and mushroom chips. A total of 27, 16 and 29 volatile flavor components were detected in fresh straw mushroom, vacuum fried chips and vacuum freeze-dried chips, respectively. The main volatile compounds in fresh straw mushroom were aldehydes (54.0%), ketones (40.27%) and alcohols (4.1%), which contributed to the delicate floral aroma and mushroom flavor. The main volatile compounds of vacuum fried chips, having a toasted flavor, were alkanes (79.83%), nitrogen and sulfur compounds (12.12%) and ketones (6.6%). Alkanes (81.07%), esters (8.54%) and nitrogen and sulfur compounds (7.9%) were the major components in vacuum freeze-dried mushroom chips, which contributed to the fruity aroma accompanied by toasted flavor. In general, the overall flavor of vacuum freeze dried chips was more diverse compared to fresh straw mushroom and vacuum fried chips.

Key words: Volvariella volvacea, vacuum fried chip, vacuum freeze dried chip, nutrient, volatile components