Fermented Okara Oyster Mushroom Protein Boosts Umami
NTU Singapore researchers used oyster mushroom mycelium to ferment okara, a soy byproduct, raising its protein content to over 30% and improving its flavor
Researchers at Nanyang Technological University, Singapore (NTU Singapore) have fermented okara with oyster mushroom mycelium, significantly boosting its protein and improving its flavor. The protein content of the fermented soy pulp rose to between 27.7% and 30.2% by dry weight.
The team used a solid-state fermentation process where the fungus grows directly on moist okara. Over an 11-day incubation, the mycelium fully covered fresh okara, producing the densest growth. Enzymes from the fungus broke down the okara's complex plant fibers into simpler sugars and amino acids. This breakdown drove the nutritional shift.
Nitrogen levels, an indicator of protein, increased. Glucose concentrations surged by up to 6.4 times from a low baseline. Taste analysis with an electronic tongue showed the fermented product was less sour and more savory. Umami flavor compounds increased several times over, with fresh okara yielding the strongest result. Acids linked to sourness generally declined. Some samples, however, became more bitter and dry after fermentation, indicating the process needs adjustment for a balanced flavor.
Problem and potential
Okara is the soybean pulp left over from tofu and soy milk production. Soy food producers generate it in large volumes. Its high moisture content causes rapid spoilage. Its insoluble fiber, coarse texture, and relatively sour taste limit food applications. These properties often lead to it being discarded or used as low-value animal feed.
The research highlights a potential route to turn this by-product into a higher-value food ingredient. Professor William Chen, director of NTU’s Food Science and Technology Programme, said: "This proof-of-concept approach offers a promising way to turn okara into more valuable food ingredients." The aim is to create new opportunities for okara to support a circular and sustainable food system.
Collaboration and validation
The study was conducted in partnership with Japanese food manufacturer Ichimasa Kamaboko and published in the journal Food Chemistry: X. The lead investigator is Professor William Chen, and the first author is Dr. Malsha Samarasiri, a research fellow at NTU.
The work compared fresh and dried okara with blends containing wheat bran and sawdust. It builds on related efforts; NTU’s programme partnered with Bunge in 2024 to develop alternative protein flavors from oilseed side streams using similar fermentation.
The study remains a proof-of-concept. Further work is needed to assess food safety, shelf life, and commercial viability. Professor Chen stated that future research must cover pre-treatment, energy efficiency, scale-up feasibility, production economics, and consumer acceptance. A separate study by the team showed that oyster mushrooms grown on okara-containing substrate also gain enhanced nutritional value.
The NTU team's next steps include assessing energy requirements, food safety, storage stability, aroma profiles, and human sensory response. They will also optimize fermentation parameters and evaluate the financial case for scale-up.
