Title : From waste to ingredient: Valorization of edible mushroom stems through optimized protein recovery
Abstract:
The rising global demand for sustainable and resource-efficient food systems has intensified the search for alternative protein sources. Agro-industrial by-products, specifically the stems of edible mushrooms such as Pleurotus spp. and Lentinula edodes, represent a promising yet underexplored reservoir of high-quality proteins. Transforming these discarded residues into functional ingredients supports the principles of the circular economy while offering novel solutions for the food industry. Framed within the European project LIKE-A-PRO, which aims to mainstream alternative proteins, this study focuses on the valorization of mushroom stems. In this context, the objective of the study was to optimize the protein extraction process from Pleurotus ostreatus and Lentinula edodes by-products at laboratory scale and to evaluate its subsequent scalability for potential industrial applications.
Mushroom stems were dehydrated at 50°C for 48 h and milled to a particle size of 1 mm to obtain the starting flours. Protein extraction was carried out using a solid-to-solvent ratio of 1:20 (w/v). The study focused on optimizing the critical parameters of the extraction process, the alkaline solubilization pH (ranging from 8 to 13) and the isoelectric precipitation pH (ranging from 2 to 4).
Lab-scale optimization showed that protein extractability was significantly influenced by pH. For Pleurotus, the maximum yield of 2.49 g/100 g flour was achieved at pH 13 (solubilization) and pH 4.0 (precipitation). Under these conditions, the protein content increased from an initial 11.11% in the raw flour to 52.73% in the final extract. Similarly, Lentinula reached its optimal yield of 2.89 g/100 g at the same pH values, increasing the protein concentration from 19.37% in the flour to 40.55% in the extract. Although LE showed slightly higher recovery at pH 3.0, pH 4.0 was selected as the optimal point to standardize the process for both species and to prevent equipment corrosion and high neutralization costs during industrial scale-up.
The optimization of pH parameters successfully identified the conditions for maximum protein recovery and enrichment. The process effectively increased the protein concentration by 4.7-fold for Pleurotus and 2.1-fold for Lentinula compared to the initial flours. These parameters were subsequently validated in scale-up trials. The first upscaling was performed in a 60 L tank, processing 5 kg of mushroom stems, followed by a second upscaling in a 400 L tank treating 30 kg of raw material. At pilot scale, to enable processing of larger quantities, the solid-to-solvent ratio was adjusted to 1:10 (w/v). For Lentinula edodes, the yield was 8.3 g/100 g with a protein content of 36.63% at 60 L, and 7.0 g/100 g with a protein content of 39.23% at 400 L. For Pleurotus ostreatus, the yield was 3.4 g/100 g with a protein content of 38.45% at 60 L, and 6.0 g/100 g with a protein content of 20.10% at 400 L. The results demonstrated process robustness from laboratory to semi-pilot scale, confirming that the upcycling of mushroom stems is a technically viable strategy for producing concentrated alternative protein ingredients at an industrial level.
This work has received funding from the European Union under Grant Agreement No 101083961
Keywords: Pleurotus Ostreatus, Lentinula Edodes, mushroom By-products, Alternative Proteins, Alkaline Extraction, Upcycling, Valorization.
