Soy proteins may extend life of frozen foods

Ice cream is not nearly as creamy and comforting when it develops an unsavory coating of ice crystals. There are few food-grade cryoprotective agents, but a new study published in the Journal of Agricultural and Food Chemistry suggests that soy protein isolate (SPI)—a material widely used as an additive in the food industry—might prevent the degradation of food’s texture and taste upon freezing (2023, DOI: 10.1021/acs.jafc.2c08701) .

“This is derived from a natural food protein, so it’s nontoxic,” says Tong Wang, a food chemist at the University of Tennessee, Knoxville who led the project. “If we can prove it is effective in food, that will be a win.”

Previous work found antifreeze properties in gelatin-derived peptides, but Wang and her colleagues sought a plant-based molecule. After screening several types of plant proteins, they landed on SPI and tested several versions of it. The SPI peptides that had stronger antifreeze activity had higher molecular weights and shared some similarity in their secondary structures, Wang says.

Wang’s hypothesis is that to prevent freezing in food, molecules have to be amphiphilic—that is, they must have both hydrophobic and hydrophilic regions—and that the SPI peptides perform their protective effects at the water-ice interface.

She and her colleagues are conducting mechanistic studies to pin down how exactly SPI peptides’ chemical interactions keep ice from forming. She says that because SPI peptides are naturally derived, they’re also strong candidates for other applications, including in agriculture and for deicing roads.