BIOACTIVE-RICH MUSHROOMS FOR FOOD REFORMULATION

Rising global concerns about animal product consumption and environmental sustainability have fueled the rapid expansion of plant-based protein sources, with bioactive-rich mushrooms (BRMs) emerging as a frontrunner. Extracts and powders of BRMs are widely used as dietary supplements and functional foods, particularly in Eastern countries, due to their high nutritional value: abundant dietary fiber, proteins, vitamins, trace minerals, and bioactive compounds like lectins, phenolics, and volatile organics, all while being low in calories and fat. Cultivation of BRMs through solid-state fermentation (SSF) on agri-food by-products is inherently sustainable, reducing waste and carbon footprints. However, it is important to optimize growing conditions and to have fast and reliable methods to monitor mushroom development. Moreover, the use in food applications of BRM mycelium or whole fermented biomass, obtained through SSF, is still poorly investigated. Within this context, this PhD project investigated the potential application of BRM mycelium or fermented biomass for food reformulation, aiming to introduce innovative protein ingredients and sources of health-promoting bioactive compounds. Specifically, SSF of Pleurotus ostreatus and Ganoderma annularis was studied, using substrates such as fresh-cut mixed salad by-products, brewer’s spent grain, and apple pomace. This study was conducted within the ONFoods project, contributing to the objectives of Spoke 04 “Food Quality and Nutrition,” funded by the National Recovery and Resilience Plan (NRRP). Part of this work was conducted at IRTA Fruitcentre (Lleida, Spain) during a five-month research stay abroad. At first a literature survey comprehensively reviewed BRMs, emphasizing nutritional composition (proteins, fibers, micronutrients), as well as cultivation techniques (i.e., SSF and submerged fermentation) and parameters (e.g., substrate humidity, nutrients, fermentation temperature). The survey pinpointed knowledge gaps and enabled the selection of BRM strains to investigate. Then, SSF of P. ostreatus and G. annularis on agri-food by-products (i.e., fresh-cut mixed salad by-product, brewer's spent grain) were performed and advanced methods for monitoring were developed, based on digital imaging, active thermography, and Fourier-transform near infrared (FT-NIR) spectroscopy. Moreover, the mycelial biomasses were analyzed for protein, lipids, polyphenols, and β-glucan content to evaluate the quality obtained. Another SSF trial was set up to optimize growing conditions of P. ostreatus on apple pomace, considering the type of inoculum (I.e., liquid and solid), the container (i.e., trays with lid, trays in bags, and bags), and the type of wetting solutions (i.e., no solution, water, nutrient-enriched solution, and aquafaba – cooking water of chickpeas) as experimental factors. The results demonstrated that the best combination consisted in the use of the solid inoculum, trays closed in bags and aquafaba as wetting solution. Both the mycelium and the whole fermented biomass were evaluated and the products obtained under the optimized conditions were dried for the following food applications. The final part of the work focused on food reformulation incorporating the BRM biomasses previously produced. High-consumption staple products were considered, like cookies and gluten-free (GF) bread, but also innovative prototypes were developed, including miso-like paste and 3D-printed products, demonstrating BRM versatility. GF bread was reformulated by partially substituting (at 5, 7.5, and 10%) rice flour and corn starch with P. ostreatus mycelium powder obtained from fresh-cut mixed salad by-product, resulting in an improved nutritional profile but reduced specific volume and crumb softness compared to the reference product. Cookies were reformulated by replacing wheat flour (at 5 and 10%) with P. ostreatus mycelium or whole fermented biomass powders obtained from apple pomace. No notable differences were observed in dough properties, whereas clear differences emerged in the final product, which maintained compositional characteristics comparable to reference samples while potentially exhibiting higher levels of bioactive compounds due to fermentation-derived products. A sweet miso-like product was developed by substituting (at 50 and 100% level) soybeans with fresh whole fermented biomass of P. ostreatus and apple pomace. After maturation, products with good microbial quality as well as physical and chemical properties closely aligned with traditional miso were obtained. At last, 3D-printed prototypes suitable for dysphagic patients were developed using the powders of P. ostreatus mycelium and whole fermented biomass produced through SSF on apple pomace. For comparison, a powder of commercial P. ostreatus fruiting bodies was also used. The effect of methylcellulose addition (1%) was evaluated as well. The results obtained indicated that the prototypes showed satisfactory technological properties (i.e., printability and texture of the final product), thereby supporting the potential for innovative applications of fungi biomasses in this context. To maximize the potential of BRMs in food and health-related industries, future research should prioritize the development of biomass scalable production methods and the investigation of sensory properties and acceptability of the innovative food products, as well as the bioavailability of key nutritional compounds.