Nutritional Quality of Oyster Mushroom As Affected by Drying and Pretreatments

Oyster mushrooms (Pleurotus ostreatus) are the second most widely grown mushrooms in the world, valued for their monetary worth, medicinal properties, nutritional quality and unique flavor. Oyster mushroom production does not require high technology or large capital investment thus it has potential to help improve livelihoods in resource limited communities. However, a major drawback is that oyster mushrooms are highly perishable. Most research has been focused on preservation methods that are more adoptable to large scale operation than household   production. While reports on sensory quality evaluations are available, studies on nutritional  changes associated with postharvest treatments are largely lacking. There is need for simple and efficient preservation methods that can maximize quality and be easily adopted at household level, especially in communities where food availability and nutrition are a constant challenge. An experiment was conducted to evaluate the effectiveness of postharvest treatments and drying methods on the nutritional quality of oyster mushrooms. Two drying treatments (oven and solar), three blanching treatments (water, steam, and no blanching) and four chemical pretreatments (lemon juice, vinegar, potassium bisulfite, and no chemical) were evaluated. The experiment was laid out in a randomized complete block design with factorial arrangement. Dried mushrooms were evaluated for minerals, ergothioneine, protein, and antioxidant capacity. Analysis of variance was made (SAS program) with least significant differences used to separate means. Blanching and chemical treatment were shown to reduce the protein content. Higher K, Mg, Mn, P, Na, and Fe were found in the steam blanched and non-blanched mushrooms when compared to the water blanched mushrooms. Higher Ca, Mg, Na, and P were found in mushrooms treated with lemon and vinegar when compared with potassium bisulfite, while higher Zn was found with the potassium bisulfite treatment. No differences in mineral content were observed between the solar and oven dried mushrooms.