Drying of MushroomsFresh mushrooms with a moisture content of 85-90% were air-dried at 40-45°C to a final moisture content of 10%. The dried mushrooms were later used for the extraction of flavour compounds.
Isolation of Volatile CompoundsFresh (300 g) and dried (30 g) mushrooms were cut into small pieces and homogenized in a Waring blender (Braun, Model-MX-32-2, Germany) at low speed with 600 ml distilled water for 2 min. The homogenate was subjected to simultaneous distillation and solvent extraction under reduced pressure in a Likens and Nikersontype apparatus, 8 using diethyl ether as the extraction solvent. The volatiles were collected at 15°C, dried over anhydrous sodium sulphate and concentrated to 0.1 ml at 35°C bath temperature. This experiment was replicated three times.
Gas ChromatographyAnalysis was performed on a Perkin-Elmer Autosystem-XL gas chromatograph fitted with 30 m × 0.25 mm i.d. PE-wax (stationary phase, polyethylene glycol) and PE-1 (stationary phase, polydimethylsiloxane) (Perkin-Elmer, USA) fused silica capillary columns. The operational conditions were: 60°C for 4 min, rising at 5°C/min to 200°C, then held for 5 min; injector and detector (FID) temperatures, 230°C and 260°C, respectively; carrier gas, nitrogen at a flow rate of 1.0 ml/min; split ratio, 1:100; sample size, 0.5 µl. The following standards were chromatographed under identical conditions: 1-octen-3-ol,
Methanolic extracts of four cultivated edible mushrooms of Pleurotus spp. namely Pleurotus florida, Pleurotus sajor-caju, Pleurotus cystidiosus and Pleurotus djamor along with the sporeless/low sporing mutants of Pleurotus florida, and Pleurotus sajor-caju were analyzed for their antioxidant activity using different chemical assays. The electrochemical behaviors of these extracts were also analyzed using cyclic voltammetry and differential pulse voltammetry. Results showed that scavenging effects on 2,2-diphenyl-1-picrylhydrazyl radicals were good (73.3-42.4 %) at 1.5 mg/ml. At 12 mg/ml, the reducing powers (2.54-1.71) and chelating effects on ferrous ions (56.0-78.5 %) were excellent. H 2 O 2 scavenging abilities at 1.5 mg/ml showed a wide range (20.0-85.4 %). Scavenging of superoxide radicals were excellent and were found to be in the range of 61.1-90.0 % at 16 mg/ml concentration. FRAP results were in the range of 1.20 -0.98 at 16 mg/ ml. Total phenolic and total flavonoid contents of the methanolic extracts ranged from 22.67 to 36.03 mg/g and 1.19-2.94 μg/g respectively. The study assessed the amount of variation in antioxidant activities exhibited by different cultivated species and their sporeless/low sporing mutants.
The sporophores of Pleurotus are gymnocarpous and continuously release spores in the atmosphere causing respiratory allergies like hay fever and farmerÕs lung disease among workers. The allergy is caused by the antigens present on the walls of the spores. Apart from this, during commercial production, these spores settle on the fruit bodies, germinate and form a velvety film which gives an unpleasant appearance to the mushrooms. The spores emitted may include new genotypes likely to attack wood or trees. Spore allergy is one of the most important limiting factors for the large scale cultivation of this species. Different approaches are being adopted at IIHR for the production of commercial sporeless/low-sporing strains of Pleurotus to alleviate the spore allergy problem. Attempts were made during the present investigation to produce sporeless or low-sporing mutants through u.v. mutation. Mutation of the mycelium did not yield the desired results. Mutation of the spores of Pleurotus sajor-caju yielded an extremely low-sporing mutant after 75 min exposure. The character has been found to be stable for more than 10 generations of subculturing.
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