Preliminary Shelf Life Studies of In-vitro Antioxidant Potential of Gamma Irradiated Dried Mushrooms (Pleurotus ostreatus Ex. Fries) Kummer in Ghana

Aim: Antioxidant potential of dried and gamma irradiated mushrooms (Pleurotus ostreatus) were assessed over a 12 months storage period.

Place and Duration of Study: Laboratory work was carried out at the Applied Radiation and Biological Centre, Radiological and Medical Research Institute, Ghana Atomic Energy Commission, Accra. From 25th June 2013 to 25th June 2014.

Methodology: Mushrooms were stored in polythene and polypropylene packs and were irradiated with ionizing radiation from a cobalt-60 source at doses of 0.5, 1, 1.5, 2 kGy at a dose rate of 1.7 kGy/hr at room temperature of 28-30°C. The control was not irradiated. Total phenolic contents, flavonoids and free radical scavenging activity DPPH (2, 2'-diphenyl-1-picrylhydrazyl) were examined at 0, 3, 6 and 12 months of storage using aqueous, ethanol and methanol extracts by Folin-Ciocalteu’s method.

Results: Total phenolic content ranged from 0.50±0.01- 10.96±1.7 mg/GAE, flavonoids ranged from 1.64±0.05- 8.90±0.6 mg/QE, DPPH radical scavenging activity also ranged from 6.85±0.10- 13.03±0.04% and IC50 values also ranged from 0.069 - 1.071 mg/ml. Both extracts and the treatment doses of mushrooms stored in polythene and polypropylene packs differed significantly (P<0.05). Good linear correlation was confirmed between the values for the total phenolic content and antioxidant activity of mushroom extracts.

Conclusion: Pleurotus ostreatus could be regarded as a promising candidate for natural mushroom sources of antioxidants with high value due to the presence of high phenolic compounds which contribute to high antioxidant activity. Employing low dose gamma radiation by the local food industry could enhance the hygienic quality, extend shelf-life, and preserve nutrients and anti-nutrients.