Making Bean Flour More Functional

Canada is a major grower of beans, but they’re not being used to their fullest potential in food formulations, even though they’re rich in nutrients. Scientists at the University of Guelph are working to change that. They’re researching processes to convert beans into palatable, functional flour for use in baked goods.

“Beans are an excellent source of proteins, and they have a very nice amino acid composition. It’s actually better than what you would find in traditional wheats, for example, but it doesn’t have the same functionality,” says Iris Joye, an associate professor of cereal science and technology in the Department of Food Science at the University of Guelph. Joye teamed with doctoral student Navneet on the research, and their findings were recently published in the journal Food Hydrocolloids.

Bean flours don’t produce the viscosity of a wheat flour, says Navneet, and that can be a problem for applications like cakes. So the researchers used two treatments on a bean flour—a dry heat treatment and an extrusion process—to see if they could get it to function like wheat flour in a cake batter. “We wanted to keep the appearance and texture of our end product similar to what we would get with a wheat flour,” she says.

Starch is a big factor in functionality. Wheat flour contains 75% to 80% starch, while bean flours have only 40% by comparison. Joye and Navneet could have added more starch to get bean flour to behave more like wheat flour, Navneet notes, but that would have meant that the end product would no longer be clean label, which they wanted to maintain. “We wanted to modify the starch properties instead of adding anything foreign to the flour, so that’s why we did heat treatments,” she says.

Functionality Changes

The researchers ground navy beans into flour. For the heat treatment, an even 0.5 cm layer of bean flour was spread on an aluminum pan and placed in a convection oven at a range of temperatures from 120°C to 190°C for 15 minutes. The extrusion samples were prepared with a moisture content of 22% and 30% and two screw speeds at 250 rpm or 500 rpm.

“We wanted to test how each treatment was able to modify starch and protein differently and which one we can consider as an optimal treatment for further use in an end product,” explains Navneet.

The researchers found the optimal time and temperature for the heat treatment is 190°C for 15 minutes. “A simple heat treatment changed the functionality of the bean flour quite drastically,” says Joye.

The dry heat didn’t much impact the starch, but it did change the protein structure; in fact, the temperatures between 130°C and 180°C didn’t really change anything. But extrusion changed both the protein structure and the starch.

They found that each treatment resulted in very different functionalities of the bean flour, says Joye. That means they could be used to alter the flour’s composition depending on the outcome desired. “There’s a lot [more] versatility and a lot of fine-tuning we can do with those physical techniques to modify flours than we currently are fully taking advantage of,” she says.

Gluten-free bakery products are an obvious initial application for bean flour. Generally, Joye says, gluten-free products are high in carbohydrates and low in proteins. A bean flour with the right functionality could improve both the carb and protein content in those products, she says.

The researchers are continuing their work with bean flours. They have been optimizing the extrusion process and have a research paper in the works. Another research group at the University of Guelph did a sensory study of cakes using the optimized bean flour and gave the product a thumbs up. “They said it was one of the best gluten-free products they ever tasted,” Navneet says.

While beans and derivative products are an important product locally, Joye notes, their research has global implications. “We can increase the value that you can get from beans,” she emphasizes.ft