From stale bread and brewers spent grain to a new food source using edible filamentous fungi

Abstract

By-products from the food sector with a high load of organic matter present both a waste-handling problem related to expenses and to the environment, yet also an opportunity. This study aims to increase the value of stale bread and brewers spent grain (BSG) by re-introducing these residues to the food production chain by converting them to new protein-enriched products using the edible filamentous fungi Neurospora intermedia and Rhizopusoryzae . After 6 days of solid state fermentation (at 35°C, with a95% relative humidity and moisture content of 40% in the substrate) on stale bread, a nutrient-rich fungal-fermented product was produced. The total protein content, as analyzed by total amino acids, increased from 16.5% in stale sourdough bread to 21.1% (on dry weight basis) in the final product with an improved relative ratio of essential amino acids. An increase in dietary fiber, minerals (Cu, Fe, Zn) and vitamin E, as well as an addition of vitamin D2 (0.89 µg/g dry weight sample) was obtained compared with untreated stale bread. Furthermore, addition of BSG to the sourdough bread with the aim to improve textural changes after fermentation showed promising outcomes. Cultivation of N. intermedia or R. oryzae on stale sourdough bread mixed with 6.5% or 11.8% BSG, respectively, resulted in fungal-fermented products with similar textural properties to a commercial soybean burger. Bioconversion of stale bread and BSG by fungal solid state fermentation to produce a nutrient-enriched food product was confirmed to be a successful way to minimize food waste and protein shortage.

Fungi Burger from Stale Bread? A Case Study on Perceptions of a Novel Protein-Rich Food Product Made from an Edible Fungus

“…This is in line with research that has reported the smell of products made of edible filamentous fungi, such as N. intermedia, to be generally pleasant [51]. The fungi burger patties that are cultivated on bread residuals predominately smell of mushrooms but also have a nutty and fruity smell [34], which seems to be perceived as pleasant by many participants.…”

“…Preliminary laboratory research using bread residues resulted in a fungi burger patty, which has promising qualities for human consumption in terms of its texture and nutritive quality [34]. In fact, the protein content of bread can be more than doubled after fermentation for five days using the edible filamentous N. intermedia [34]. As earlier mentioned, the production of meat-based food requires large amounts of resources.…”

“…As earlier mentioned, the production of meat-based food requires large amounts of resources. The technique used by Gmoser et al [34] eliminates a large part of the supply chain of meat-based products. Fungi-based products fermented on plant-based bread residuals could, thus, be more environmentally and economically sustainable than meat-based products.…”

Techno-Economic Analysis of Bioethanol Plant By-Product Valorization: Exploring Market Opportunities with Protein-Rich Fungal Biomass Production

“…The increasing population on Earth results in protein depletion regarding food and feed sources. Protein-rich biomass, which can be obtained from, e.g., edible yeast, bacteria, and filamentous fungi, represents a potential alternative protein source for feed and food applications [16,17]. In the previous studies, it has been stated that N. intermedia, a GRAS (generally regarded as safe) microorganism, can be used for the production of nutritious food products from stale bread and brewers spent grains [17,18].…”

“…Protein-rich biomass, which can be obtained from, e.g., edible yeast, bacteria, and filamentous fungi, represents a potential alternative protein source for feed and food applications [16,17]. In the previous studies, it has been stated that N. intermedia, a GRAS (generally regarded as safe) microorganism, can be used for the production of nutritious food products from stale bread and brewers spent grains [17,18]. The product made in the form of a burger has led to general acceptance during sensorial analysis in terms of taste and structure but also regarding waste valorization perspectives [17,18].…”