Modified lentil protein mimics fat in non-fat yogurt, researchers report

UNIVERSITY PARK, Pa. — Modified lentil protein can act like fat in non-fat foods, especially yogurt, delivering creaminess and richness, according to a new study led by researchers at Penn State.

The work, published in Food Chemistry, is the latest effort to develop an effective fat texturizer for use in low-fat foods. Excessive calorie intake, particularly from full-fat products, is a key factor contributing to obesity in the United States. Although dietary guidelines recommend consumption of low-fat or non-fat products, fat reduction often compromises texture, viscosity, flavor and overall consumer acceptability, the researchers said.

Study senior author Yi Zhang, Frederik Sr. and Faith E. Rasmussen Career Development Professor in Food Science in the College of Agricultural Sciences, explained that the team is working to modify plant proteins that can act as fat replacers to make products healthier without sacrificing taste and other desirable qualities.

“Although commercial fat replacers reduce calories, they often fail to replicate the functional and sensory qualities of fat,” she said, pointing to the physical and chemical properties of fats that contribute to a consumer feeling full after eating. “There has not been much research done on plant protein-based fat texturizers, showing the need for novel fat texturizers derived from plant proteins that are low-calorie, cost-effective and have excellent functionalities across diverse food applications.”

In the study, the researchers modified lentil protein so it could act somewhat like fat in non-fat foods, especially yogurt. They used an enzyme called alcalase to partially break lentil proteins into smaller pieces called polypeptides.

The best-performing pieces, called LPP5-10, were tiny and had properties that help stabilize mixtures of water and oil, similar to emulsifiers used in food such as lecithin. These modified proteins could hold much more oil than ordinary lentil protein, the researchers reported — 752% versus 174%.

When only 0.05% LPP5-10 was added to non-fat milk, the yogurt made from it formed a stronger, more structured gel, the team found. Its mechanical texture — such as firmness, elasticity and resistance to deformation — became similar to yogurt made with whole milk, Zhang said.

Removing fat makes yogurt thinner and changes its mouthfeel, since fat is responsible for giving yogurt its creaminess, thickness, lubrication and structure. Zhang explained that, in the absence of fat, the LPP5-10 appeared to help achieve the same desirable characteristics.

“We can take plant protein, chop it into the right-sized pieces, and make those pieces behave like a fat-texturizing ingredient,” she said. “Importantly, this study doesn't mean the lentil protein chemically becomes fat or provides the same nutritional properties as fat. It means the modified protein can mimic some of fat’s physical and textural functions in food.”

Contributing to the research were first author Ishita Ghosh, who earned a doctoral degree in food science, and Federico Harte, professor of food science.

This research was supported by the U.S. Department of Agriculture’s (USDA) National Institute of Food and Agriculture and Hatch Appropriations under accession numbers 1030226 and 7005076. This content is the sole responsibility of the authors and does not necessarily reflect the views of the funders.