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: Separating things and then putting them back together is a common principle in industrial food production. Agricultural raw materials are broken down into their individual constituents, such as proteins, starches and fats, and the food industry then reassembles these building blocks into specific products.
In many cases, not all of the harvested crop ends up in the food we eat. In some instances, byproducts are formed that must be reused outside the food industry. These processing steps can also lead to the loss of dietary fibers, vitamins and minerals in the finished product.
To reduce food waste and retain as much of a food's nutritional value as possible, the research group led by Patrick Rühs, professor of food structure engineering, is looking for ways to use the harvested crop in its whole form wherever possible. For legumes, researchers have now demonstrated an astonishingly simple approach to turning whole peas, beans or lentils into a product whose fibrous structure makes it particularly appealing to the human palate. "During chewing, a directional, fibrous structure provides a distinctive bite that is familiar to—and enjoyed by—many people from meat or fish," explains Rühs.
"In meat and fish, this structure is formed by the directional arrangement of muscle fibers." Water and a freezer are all that the researchers need to turn peas, beans or lentils into a fibrous product. They call their method "freeze-structuring." First, the researchers soak the legumes and blend them finely to create a uniform distribution of starch, proteins and cell wall fragments. Heating the puree for 30 minutes at 90°C causes the starch to gelatinize together with the other constituents, and the puree becomes a gel.
The researchers freeze this gel from one side in a targeted manner using a mold that is insulated on all sides except one. This causes ice crystals to form in parallel and inward from the uninsulated side. As they grow, the crystals squeeze and compress the legume puree into thin parallel layers.
When the gel is thawed, the ice melts, but the directional, fibrous structure remains intact. The researchers tested a whole series of different types of beans, peas and lentils and were able to create a directional fibrous structure with all of them. "Our method works with legume species that together account for 96% of legume production worldwide," says Andrea Bach, a doctoral student in Rühs's group.
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