Scientists from Nanyang Technological University, Singapore (NTU Singapore), have developed a fermentation technique that could transform okara—a nutrient-rich byproduct of soy processing—into a more flavorful and protein-dense food ingredient. Okara is a fibrous residue left after making tofu or soymilk, and although it is rich in protein and fiber, it is often discarded due to its high moisture content, coarse texture, and sour taste. This new method, detailed in the journal Food Chemistry: X, involves fermenting okara with oyster mushroom mycelium, the root-like structure of the fungus. This process improves the nutritional value and flavor of okara, potentially offering a sustainable way to reduce food waste. The research was conducted in collaboration with a Japanese food company, Ichimasa Kamaboko. The team used a method called solid-state fermentation, where microorganisms grow directly on a moist solid material. They tested different formulations, including fresh and dried okara, and combined it with common mushroom-growing materials like wheat bran and sawdust. Fresh okara supported strong growth of the oyster mushroom mycelium over an 11-day period. As the fungus grew, its enzymes broke down the complex fibers in okara, releasing nutrients such as sugars and amino acids—key components of proteins. The study found that the protein content of okara increased to between 27.7% and 30.2% by dry weight, and its sugar content rose significantly as the fungus converted complex carbohydrates into simpler forms. Professor William Chen, lead investigator of the study and director of NTU's Food Science and Technology Program, explained that okara has long been underutilized due to its texture and flavor. However, the fermentation process using oyster mushroom mycelium not only improved the nutritional profile but also enhanced the flavor with a savory, umami taste. This approach could help repurpose okara into a more appealing ingredient. Chen also noted that a separate study by his team found that oyster mushrooms grown on okara-based substrates had improved nutritional value, suggesting a mutual benefit for both the byproduct and the mushrooms. To assess the sensory improvements, the researchers used an electronic "tongue," a device that measures taste traits objectively. Fermentation reduced sourness while boosting umami and overall flavor richness. The fermented okara had significantly higher levels of free amino acids, including glutamic acid and aspartic acid, which are responsible for umami. It also saw a rise in 5′-nucleotides, compounds that enhance the umami flavor. However, some fermented samples showed increased bitterness and dryness, which the researchers are working to address. These findings suggest that while the fermentation method shows promise, further adjustments are needed to achieve a balanced flavor profile. Looking ahead, the NTU team plans to refine the process by evaluating energy use, food safety, storage stability, aroma, and consumer acceptance. They also aim to optimize fermentation conditions and assess the economic feasibility for commercial use. This research highlights the potential of using fungi to transform industrial byproducts into valuable food ingredients, supporting a more circular and sustainable food system.