Response surface methodology was used to investigate the effect of brine concentration (10% -20%) solution temperature (35˚C -55˚C), and duration of osmosis (30 -60 min) with respect to water loss (WL) and salt gain (SG). The solution to sample ratio of 5/1 (w/w) was used. The Box-Behnken design of three variables and three levels including seventeen experiments formed by five central points were used for optimizing input parameters. Linear, quadratic and interaction effects of three variables were analyzed with respect to water loss and solid gain. For each response, second order polynomial models were developed using multiple regression analysis. Analysis of variance (ANOVA) was performed to check the adequacy and accuracy of the fitted models. The response surfaces and contour maps showing the interaction of process variables were constructed. The optimum operating conditions were: solution temperature 44.89˚C, brine concentration of 16.53 per cent and duration of osmosis of 47.59 min. At this optimum point, water loss and salt gain were predicted to be 44.55 per cent and 2.98 per cent respectively.

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The 0.5, 0.7 and 0.9 cm thick slices of button mushrooms were pretreated with different preservatives such as 0.5 per cent citric acid, 0.5 per cent KMS and 0.75 per cent EDTA for 10 minutes. Pretreated slices were dehydrated in a tray dryer at 40, 45, 50 and 55°C and their drying characteristics such as rate of drying, diffusion rate and re-hydration ratio were studied. The qualities of dehydrated slices were evaluated on the basis of veil opening and amino acid content. The samples dehydrated at 50°C showed better quality. The moisture diffusivity during tray drying varied from 1.05 x 10 -8 to 7.48 x 10 -09 m 2 /s and increased with drying air temperature.

Fruiting bodies of 6 mushrooms including Agaricus bisporus, Hyspizygus ulmarius, Pleurotus florida PF-01, Pleurotus florida PF-01 R5, Pleurotus platypus and Pleurotus sajor-caju PSC-04 were analyzed for antioxidative enzymatic profile during low temperature storage. Colour, rehydration ratio and moisture were taken as indices of accessing their shelf-life/marketability, of which, colour contributed significantly while rehydration ratio and moisture did not change considerably during storage. Mushrooms were stored at 5 and 10 °C and activities and isozyme profile of antioxidative enzymes, superoxide dismutase (SOD) and peroxidase (POX) were analyzed after every 48 h interval till the fruiting bodies remained marketable. SOD activity increased generally at 5 and 10 °C while POX activity first increased and then decreased under similar conditions. Isozyme profile of SOD and POX did not show any new isozyme during storage, the only difference was in the intensity of bands.

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