Effect of pretreatments and drying techniques on quality of Calocybe indica (P & C) and Pleurotus eryngii (DC.:Fr.) Quél)

In the present study, Calocybe indica (P & C) strain C-3 and Pleurotus eryngii (DC.:Fr) Quél strain DMR-P-257 were grown on wheat straw. Average yield obtained from Calocybe indica was 519.3 g (BE = 64.9%) per bag and it was 173.06 g (BE = 25.98%) from Pleurotus eryngii. Effect of pretreatments and drying techniques on the quality of Calocybe indica and Pleurotus eryngii was analyzed. C. indica and P. eryngii fruit bodies were sliced and pretreated with the treatments like blanching (100 ̊C) and steeping in different concentrations of potassium metabisulphite (500 ppm, 1000 ppm and 1500 ppm) and citric acid (500 ppm, 1000 ppm and 1500 ppm) at room temperature. Pretreated and control samples were dried in cabinet tray dryer, solar dryer and in open sun drying until constant weight was gained. The dried products were ascertained in many respects for storage time period of three months. Solar dried and cabinet dried milky mushroom showed no significant difference in the L values. In the KMS treated C. indica, maximum whiteness (L value = 90.46) was observed. In P. eryngii citric acid treated samples gave better color during solar and cabinet drying. Rehydration ratio (4.71) was at peak in citric acid (500 ppm) treatment in open sun drying of milky mushroom. The P. eryngii samples dried in open sun and cabinet tray dryer showed maximum rehydration ratio (6.55) when treated with 500 ppm citric acid. 1500 ppm of citric acid gave the more harder products (84.59 N) of C. indica in all types of drying. In P. eryngii maximum hardness (48.33) was observed in cabinet dried samples when treated with 1000 ppm concentration of citric acid. Micro structural evaluation of cabinet dried C. indica indicated the severe tissue shrinkage. Scanning electron micrographs of solar dried King Oyster mushroom showed the more porosity. In blanched milky mushroom as well as King Oyster mushroom, poor rehydration ratio, maximum hardness, minimum whiteness and bacterial count were observed. Maximum protein content (23.16 g/100g of mushrooms) was recorded in sun-dried mushrooms when washed with citric acid (500 ppm) and KMS (500 ppm) in C. indica . Whereas maximum range of carbohydrates (51.05 g/100g of mushrooms) was observed in cabinet dried milky mushrooms when given a treatment of KMS (500 ppm). Lipid content was found maximum (5.29 g/100g of mushrooms) in solar dried milky when treated with citric acid followed by KMS at the 500 ppm concentration. In P.eryngii, maximum protein content (25.68 g/100g of mushrooms) was found in 500 ppm treated citric acid followed by 500 ppm KMS when dried in open sun that is 25.12g/100g of mushrooms. Lipid content of cabinet dried King Oyster mushroom was observed maximum (4.75g/100g of mushrooms) when pretreated with KMS (500 ppm). Maximum value of carbohydrate content was observed in sun dried and solar dried samples when treated with citric acid (500 ppm) followed by KMS (500 ppm) treated. Observations indicated that solar drying was the best among the three drying techniques as it gave best results upto the three months of storage in both the mushrooms, when the samples were pretreated with KMS (500 ppm) or citric acid (500 ppm). It gave the maximum nutritional values i.e proteins, carbohydrates and lipids followed by cabinet drying.