Fermented okara could improve metabolism, tackle obesity

Scientists from Nanyang Technological University, Singapore (NTU Singapore) and Waseda University in Japan have found that fermented soybean waste, or okara, could improve fat metabolism and mitigate the effects of diet-induced obesity. With 14 million tonnes of okara generated every year, and nearly a third of the world’s population overweight or obese, the scientists hope their findings may pave the way for fermented okara to be integrated into health foods one day, addressing the problems of food waste and obesity at the same time.

To enhance the nutritional profile of okara, the research team first fermented okara collected from a Singapore bean curd manufacturer using a process traditionally used in Asian countries to make fermented soybean food products such as miso, soy sauce and tempeh. Enhancing the nutritional profile of okara increases its potential as a desirable ingredient in the human diet, the scientists said.

The team added a mix of Aspergillus oryzae and Aspergillus sojae — food-grade microbes — to okara and left it to ferment in the dark at 25°C for four days. Compared to unfermented okara, the scientists found that fermented okara had more protein and a higher total phenolic content — an indication of higher antioxidant properties — and less insoluble dietary fibre.

The scientists then investigated the anti-obesity effects of fermented okara on mice put on a three-week high fat diet compared to mice put on three other types of diet: a normal diet, a high-fat diet and a diet supplemented with unfermented okara. Their results were published in the journal Metabolites.

At the end of three weeks, mice that were fed fermented okara every day gained the least body mass (3 g), while the other three groups gained between 6 and 10 g. The mice that were fed fermented okara also had less visceral and subcutaneous fat (30 and 19 g respectively) than mice on a high-fat diet without any fermented okara (67 and 53 g respectively).

The scientists also found lower triglyceride and cholesterol levels in mice on a fermented okara-supplemented diet compared to those without, the former being a type of fat in the blood that has been linked to an increased risk of heart disease. Further investigation revealed that the reduction in triglycerides was in part due to a significant dip in proteins involved in fatty acid synthesis.

“Our findings suggest that fermented okara could help to mitigate the harmful effects of a high-fat diet, and could potentially be integrated in the diets of obese patients who find it difficult to make immediate lifestyle changes,” said NTU’s Dr Ken Lee, co-lead author of the paper.

The study builds on the team’s earlier research on other uses for okara. For instance, the scientists showed that fermented okara could help to bring down blood sugar levels. They have also worked with a local brewery to integrate okara into modern dishes. The researchers are now reaching out to industry partners to translate their work into healthy snacks and exploring how it can be integrated into other food products.

Image credit: ©stock.adobe.com/au/Caito

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