Collagen peptides derived from bovine collagen inhibited ice re-crystallization in super cooled ice cream, according to research from the University of Wisconsin-Madison. These findings could improve the quality of several types of frozen food.

“Uncontrolled growth of ice crystals beyond 40 micrometer size affects the quality of several frozen foods, including ice cream and frozen dough products” like frozen pizza, Srinivasan Damodaran, PhD, told Food Quality. Dr. Damodaran is professor and chair in the Department of Food Science at the University of Wisconsin-Madison.

“We have shown that short peptides derived from collagen/gelatin are able to inhibit ice re-crystallization in frozen foods,” he said. “Inclusion of these peptides in frozen foods should improve the keeping quality and consumer acceptability of these food products.”

For instance, when added to ice cream, these peptides maintain smooth ice cream texture during storage in a typical household freezer, Dr. Damodaran said.

“These ice-structuring peptides [ISPs] can be used in all frozen foods to control texture,” Dr. Damodaran added. “Inhibition of ice re-crystallization in frozen foods should help in uniform distribution of water in the food matrix and thus help in uniform heating of these products during cooking in a microwave or regular oven.”

Ice-Structuring Peptides

Dr. Damodaran and ShaoYun Wang, PhD, associate professor in the Department of Food Science at Fuzhou University in Fuzhou, China, created collagen peptides from Alcalase hydrolysis of bovine gelatin. These ISPs inhibited ice re-crystallization much like natural antifreeze proteins.

These short peptides “bind to ice nuclei or to small nascent ice crystals via hydrogen bonding and inhibit their growth,” Dr. Damodaran said. “The exact mechanism is not yet clear, but we are working on this.”

The researchers found that the optimal conditions for producing ISPs were hydrolysis at pH 9.0 for 30 minutes at 45ºC and an Alcalase-to-gelatin ratio of 0.176 unit per gram of gelatin. They also found a link between the molecular size distribution of collagen peptides and the amount of ice-structuring activity. The results showed that collagen peptides in the mass range of 600-2700 Dalton were the most effective re-crystallization inhibitors.

Concerns About Study
“Mechanistically, [the authors] argue that the collagen peptides are flexible and work by fitting to ice,” says Peter L. Davies, PhD, FRCS, Canada Research Chair in protein engineering, Department of Biochemistry, Queen’s University, Kingston, Ontario, Canada. “On the contrary, almost all the natural ice-structuring proteins are quite rigid, and there are arguments to be made why this is important for ice binding.”

Dr. Davies had additional concerns about the study. “The collagen hydrolysate needs to be present in quite high concentrations compared to the ice-structuring proteins currently used in ice cream,” Dr. Davies told Food Quality. “Also, it is not that good at inhibiting ice re-crystallization if you compare the results to the starting material. Some collagen fractions are better at re-crystallization than others, but the study should have done a direct comparison with some of the natural ice-structuring proteins. My guess is that the ice structuring proteins will be far more effective at comparable concentrations.”

The potential for these peptides extends beyond improving frozen food quality, said Dr. Damodaran. “In pharmaceutical/medical areas, these peptides, which should be mostly non-antigenic, can be used to preserve organs and tissues. In the future, some of these peptides can be incorporated into crops to make them freeze resistant/tolerant.”