EFFECT OF PRETREATMENT AND DRYING ON THE QUALITY OF OYSTER MUSHROOMS ( PLEUROTUS OSTREATUS )

Fruiting bodies of oyster mushroom were dried by hot-air drying, vacuum-drying and freeze-drying in order to compare food qualities after drying. Prior to drying, mushrooms were subjected to blanching or dipping in sodium metabisulphite solution (1 or 5 g/L), or dipping in citric acid solution (1 or 5 g/L). Drying of raw mushrooms was taken as a control. Blanching reduced the attractiveness of dry mushrooms; sodium metabisulphite improved it. It has been found that pretreatment and drying method affect the course and rate of drying. Samples subjected to hot-air drying and vacuum-drying were darker than those freeze-dried, which were clearly more attractive. The hot-air and vacuum-dried mushrooms on rehydration were inferior in quality to the freeze-dried samples. Flavor of the freeze-dried mushroom was not significantly different from that of the hot-air dried mushrooms. Food quality of dried mushrooms depends significantly on the type of drier used.