ABSTRACT Due to the biological nature of mushrooms, it is possible for them to rapidly deteriorating at postharvest if appropriate preservation efforts are not made. This study therefore investigated the effect of different pretreatment methods on selected quality parameters, antioxidants, and in vitro antidiabetic activities of elm oyster mushroom using the principal component analysis (PCA) approach. Freshly harvested elm oyster mushroom fruiting bodies were sorted, thoroughly washed, drained, and divided into four samples. The four samples were untreated, hot water blanched, steam blanched, and pretreated by brining, respectively. The samples were dried, blended, packaged, and labeled. They were analyzed for proximate, antinutrient, antioxidant, and antidiabetic activities as well as the total phenol and flavonoid contents. The data collected were subjected to statistical analysis (ANOVA and principal component analysis). It was observed that the protein, ash, and fat contents of the hot water and steam blanched samples decreased with the increasing temperature of pretreatment. There were significant ( p < 0.05) reductions in the activities of the evaluated antioxidant and in vitro antidiabetic properties of the hot water blanched samples, whereas the 0.5% soaked showed opposite trends for these activities. These may be associated with the degrading effect of heat treatment on the bioactive compounds. The antinutrients, phytate and oxalate, also decreased with higher pretreatment temperature. Overall, the antioxidants and in vitro antidiabetic activities of the samples soaked in 0.5% NaCl solution for 5 min were least affected when compared with the control sample. This was also suggested by principal component analysis that grouped the pretreatment methods according to their effects on the quality parameters of the mushroom samples. This showed that pre‐treating the mushroom samples soaking in 0.5% NaCl solution for 5 min may be explored as an effective pretreatment method for both household and commercial processing of Hypsizygus ulmarius with less deteriorating effect on the bioactive compounds.
Ogunsade et al. (Mon,) studied this question.