This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Scientists from Nanyang Technological University, Singapore (NTU Singapore) have demonstrated in a lab-scale study a fermentation method that could transform okara, a nutrient-rich soybean byproduct from tofu and soymilk production, into a more flavorful and protein-rich food ingredient. Okara is produced in large quantities by the soy food industry, but its high moisture content makes it highly perishable.
Its high insoluble fiber content, coarse texture and relatively sour taste also limit its use in food. As a result, it is often discarded as food waste or used as low-value animal feed. In a paper published in the journal Food Chemistry: X, the NTU research team demonstrated that fermenting okara with oyster mushroom mycelium—the fine, rootlike network of a fungus—substantially improves its nutritional and taste profiles.
The proof-of-concept findings suggest that mushroom-based fermentation offers a promising approach to upcycle okara into a more palatable ingredient, which could help reduce food waste and support sustainable food production, subject to further process optimization. The NTU research team conducted the study in partnership with a leading Japanese food manufacturing company, Ichimasa Kamaboko. The researchers used solid-state fermentation, a natural process in which microorganisms grow directly on a moist solid material.
They tested various formulations, including fresh and dried okara, as well as mixtures of okara combined with common mushroom-growing materials like wheat bran and sawdust. Fresh okara supported dense growth of the oyster mushroom mycelium, which fully covered the material over an 11-day laboratory incubation period. As the fungus grew, its natural enzymes broke down the complex plant fibers of okara into simpler, more digestible nutrients, releasing beneficial sugars and amino acids (the building blocks of protein).
The researchers found that fermentation increased the nitrogen level of okara, one of the indicators of protein content. Lab analysis showed the protein content increased to between 27.7% and 30.2% by dry weight. Fermentation also increased glucose concentrations by 2.8 to 6.4 times from low initial baseline levels as the fungus converted complex carbohydrates into simpler sugars.
Lead investigator of the study, professor William Chen, director of NTU's Food Science and Technology Program, School of Chemistry, Chemical Engineering and Biotechnology (CCEB), said, "Okara is a soybean byproduct that is rich in nutrients, but its high fiber content, short shelf life and less appealing flavor have long limited its use in food products for people. "Our findings show that oyster mushroom mycelium can naturally improve okara by changing its composition and producing compounds that give it a savory, umami taste. In addition, a separate study by my team also showed that oyster mushrooms grown on a substrate containing okara have enhanced nutritional value.
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