Edible antifreeze to offer ice cream advances

Ice cream formulated with gelatin hydrolysate contained smaller and fewer ice crystals than ice cream that did not contain the ingredient, writes Srinivasan Damodaran in the Journal of Agricultural and Food Chemistry .

The ingredient, produced by the enzymatic action of papain on gelatin, could offer a solution to the formation of ice crystals in ice cream.

"Although ice crystals in the range of 15 to 20 micrometres bestow a desirable smooth texture to the ice cream, those that are larger than 40 micrometres impart an unacceptable coarse and grainy texture to the ice cream ," explained Damodaran, professor of food chemistry at the University of Wisconsin, Madison. "

Temperature fluctuations during storage and handling of frozen foods promote ice crystal growth. "

Several different ingredients have been investigated for their potential to prevent the growth of ice crystals in frozen food, their efficacy is debatable, suggested Damodaran.

The solution to this problem could be gelatin hydrolysate, he said.

Ice cream was prepared with and without the ingredient and the temperature alternated between minus 14 and minus 12 degrees Celsius in order to measure the formation of ice crystals.

The greatest inhibition of ice crystals was observed for the hydrolysate fraction that contained peptides in the 2,000 to 5,000 Dalton (Da) range, reported the researchers.

The pH of the hydrolysis was also to have to an effect on the growth of ice crystals.

Indeed, the optimum conditions for hydrolysis are reported to be 10 minutes at pH 7 and 37 degrees Celsius with a papain to gelatin ratio of 1:100.

"The ice crystal growth inhibition by gelatin peptides might follow a mechanism similar to that of antifreeze proteins (AFP) and antifreeze glycoproteins (AFGP)," wrote Damodaran.

This is explained as binding between the oxygen atoms at the surface of the gelatin hydrolysate and the ice, which prevents the growth of large ice crystals in the ice cream mix.

"Further elucidation of the molecular interactions responsible for ice crystal growth inhibition by peptides from gelatin hydrolysate may lead to rationale designing of peptide cryoprotectants with greater antifreeze activity," concluded Damodaran.

According to a Euromonitor study companies in the ice cream market need sensitivity to changing regional tastes, exotic flavour mixes, labelling and packaging to be successful in attacking Western Europe's stagnant ice cream market Sales of ice cream decreased by 0.4 per cent to US$20.3bn in 2004 in the region, according to Euromonitor.

Processors are focusing on introducing unusual flavors and premium brands to hold on to their market shares.

Source: Journal of Agricultural and Food Chemistry Volume 55, Pages 10918-10923, doi: 10.1021/jf0724670 "Inhibition of Ice Crystal Growth in Ice Cream Mix by Gelatin Hydrolysate" Author: S. Damodaran