Effect of Pre-Treatments and Drying Methods on the Chemical Quality and Microbial Density of Wild Edible Oyster Mushroom

Abstract

This study was carried out to evaluate the effect of pretreatments and drying methods on the chemical quality and microbial density of wild edible oyster mushroom. The mushroom samples were pretreated by steeping in 0.5% citric and sodium metabisulphite at room temperature for 10 minutes before being subjected to sun and cabinet drying until a constant weight was reached. The dried samples including the control samples (Samples not pretreated with chemicals) were evaluated for proximate, mineral composition and microbial density. The proximate analysis (protein, ash, fat, moisture and fi bre) showed that untreated mushroom samples (both sun and cabinet dried) had the overall best results followed by samples pretreated with 0.5% sodium metabisulphite while samples pretreated with 0.5% citric acid had the lowest values. The mineral analysis (calcium, sodium, magnesium and potassium) of the mushroom samples followed the same trend as the proximate analysis. The microbial density of the samples showed that samples pretreated with 0.5% citric acid had the lowest count followed by samples pretreated with 0.5% sodium metabisulphite while the untreated samples had the highest microbial density. This implies that pretreatment with citric acid and sodium metabisulphite reduced the microbial density which may invariably extend the storage life of the edible oyster mushroom.