Process-driven flavour modulation in soybean-based alternative proteins via Neurospora crassa coculture fermentation

Area of Science:

• Food Science and Technology
• Microbiology
• Biotechnology

Background:

• Soy-based ingredients in plant-based foods often suffer from undesirable lipid-derived off-flavors like 'beany' and 'green' notes.
• Microbial fermentation presents a sustainable, clean-label approach to enhance the flavor profile of soybean ingredients.
• Optimizing fermentation conditions is crucial for controlling microbial dynamics and metabolite production for desired flavor outcomes.

Purpose of the Study:

• To optimize solid-state fermentation of soybeans using two distinct coculture systems: fungal-fungal (Neurospora crassa-Rhizopus oryzae) and fungal-bacterial (Neurospora crassa-Lactiplantibacillus plantarum).
• To investigate the effects of fermentation temperature, inoculum ratio, and duration on microbial activity, metabolite profiles, and sensory characteristics.
• To elucidate the distinct metabolic pathways governing flavor development in response to different coculture systems.

Main Methods:

• A factorial experimental design was employed to optimize solid-state fermentation parameters (temperature, inoculum ratio, duration).
• Two coculture systems were evaluated: fungal-fungal (N. crassa-R. oryzae) and fungal-bacterial (N. crassa-L. plantarum).
• Microbial dynamics, metabolite formation (e.g., amino acids, organic acids, nucleotides), aroma profiles, and sensory perception were analyzed using multivariate analysis.

Main Results:

• Fermentation significantly reduced undesirable beany odorants, with hexanal levels decreasing by up to 95% compared to controls.
• The fungal-bacterial system favored a carbohydrate-driven pathway, enriching umami metabolites like glutamic acid and peptides.
• The fungal-fungal system exhibited a lipid-driven pathway, increasing savory volatiles such as 2,4-decadienal through enhanced lipolysis.

Conclusions:

• Distinct metabolic pathways (carbohydrate-driven vs. lipid-driven) were identified for the fungal-bacterial and fungal-fungal coculture systems, respectively.
• Fermentation parameter optimization allows for targeted flavor engineering in soybean-based products.
• This study provides a framework for developing tailored flavor profiles in alternative proteins through fermentation.