Optimization of the transformation process of Agaricus bisporus and Pleurotus ostreatus co-products into flours with potential food uses

The mushroom industry generates large amounts of stem co-product. This is produced after mushroom harvests; stems are attached to the peat and growth substratum, and their only use has traditionally been as compost. In this study, we developed an alternative and profitable solution to Agaricus bisporus and Pleurotus ostreatus stems optimizing the obtention of intermediate food products by applying only physical processes, including cleaning and drying to retain food safety. The stems have a composition similar to that of the fruiting bodies, so the flour obtained could have several food applications, such as a fortifier in the development of functional foods due to its healthy nutritional composition and the amount of valuable compounds.

Four methods of cleaning the stem of A. bisporus (ABS) were developed (pre-drying, brushing, abrasive peeling, and immersion in chlorinated water). The results elucidated the use of abrasive peeling as the most suitable cleaning method with the highest colorimetry values in lightness (L*) (73.22) and the least protein content (0.26 g protein / 100 g fresh) that could be related to the peat lost. On another hand, ABS and P. ostreatus steams (POS) were dried in a freeze-dryer, a dehydrator, and an oven. Dehydration was the most economical and less invasive method, with L* of 68.19 in ABS and 81.62 in POS. In addition, three dehydration temperatures (40, 50, and 60ºC) were compared. In the case of 50ºC, the concentration of phenolic compounds (3.32 and 7.69 mg GAE / 100g fresh ABS and POS, respectively) was similar at 40ºC and higher at 60ºC. In conclusion, ABS should be cleaned by abrasive peeling to maintain food safety. On the other hand, drying ABS and POS in a dehydrator at 50°C could be a suitable process to obtain intermediate food products in the development of functional foods.