Effect of pretreatments and drying air temperature on the quality of dehydrated oyster mushroom, Pleurotus sajor-caju

摘要

Experiments were conducted on air-drying of oyster mushroom with pretreatment of potassium metabisulphite (KMS) and blanching to investigate the effect of pre-treatments and drying air temperatures on drying characteristics of mushroom and the qualityof dried oyster mushroom. Drying was accomplished in a cabinet dryer using hot air ranging from 50 to 70°C. The time required for drying of mushroom from initial moisture content of 93 - 95 % (wb) to a final moisture content of 6.5 - 7.5 % (wb) was found to be 150 to 240 min. The drying characteristics of mushroom were not affected by the pre-treatments. Final moisture content or equilibrium moisture content (EMC) of dehydrated mushroom was also not affected by the pre-treatments. However, the rate ofdrying increased with the increase in drying temperature. Increase in drying temperature significantly reduced the total drying time. Pre-treatments and drying temperatures had influence on the rehydration ratio (RR), hardness and colour of the dehydrated mushrooms. Adverse effect of drying air temperature on RR, hardness and colour was observed. Blanching improved the colour of the dehydrated mushroom but increased hardness. Blanched sample dried at 70°C resulted in the maximum hardness (2.10 N). Aloss of approximately 20 % protein was observed during blanching.