Researchers aim to retard mold growth on shredded cheese

Dec. 15, 2003
Though work remains to be done, an FDA-approved antimicrobial preservative is showing promising results

In order to boost cheese sales for retailers and provide consumers with higher quality cheese products, Dairy Management Inc. (DMI) is leading research efforts to retard mold growth on the surface of cheeses.

Researchers Joseph Marcy and John Koontz are inhibiting mold growth on the surface of cheeses by leveraging natamycin, an antimicrobial preservative approved by the Food and Drug Administration (FDA) for use in the food industry. Natamycin is particularly beneficial when used on shredded cheeses, which are especially prone to mold.

Early in their research, Marcy and Koontz pinpointed and began to address two potential challenges: Natamycin is practically insoluble in water, and its stability is degraded during the ripening and storage of cheese.

Natamycin's tendency toward insolubility makes it difficult to apply to cheese surfaces. In its original form, natamycin is a dry powder that must be mixed in an aqueous solution to form a liquid that can be applied to food products. However, during that application process, aqueous natamycin suspensions can clog spray nozzles and prevent a uniform distribution of the substance onto the cheese surface. Once the spraying hurdle is overcome, the second part of the challenge arises.

"In terms of stability, natamycin is extremely sensitive to ultraviolet (UV) light," said Marcy, professor of food science and technology at Virginia Polytechnic Institute and State University in Blacksburg, Va. "Cheese products are exposed to high-intensity fluorescent lighting in the retail dairy case, resulting in natamycin degradation on the cheese by the time of purchase by consumers."

Marcy and Koontz set out to increase the water solubility and chemical stability of natamycin to improve the delivery system and product quality of shredded cheese They addressed these issues by forming molecular inclusion complexes of natamycin with cyclodextrins in order to increase its solubility and chemical stability.

"In these inclusion complexes, we found that more than 90 percent natamycin remained in the aqueous solution and it was significantly more stable than free natamycin," said Marcy. "When addressing the issue of stability, we found that product packaging helped to greatly reduce natamycin photodegradation."

The research is ongoing, and the results to date are promising. "The accomplishment of these objectives should dramatically increase the antifungal efficiency of natamycin and, therefore, allow consumers to purchase shredded cheese products of greater quality," concluded Marcy.



The whey to healthier snacks

Whey proteins that are left over after cheese making are a key ingredient in new nutritious snack foods produced under a process developed by the U.S. Dept. of Agriculture's (USDA) Agricultural Research Service.

ARS recently filed a patent on the process, which uses a twin screw extruder, to make crunchy snacks with whey proteins. The technique already has drawn the interest of food companies.

By using whey, the process boosts protein in expanded snacks such as cheese curls from the traditional average of 2 to 5 percent to 35 percent.

Most crunchy snacks are made from high-starch products such as corn flour, according to Charles Onwulata, a food technologist at the ARS Eastern Regional Research Center in Wyndmoor, Pa. An extruder consisting of a long, heated barrel with two mixing screws inside, cooks the starch as the screws mix and push it through the equipment to form the snack food. The crunchiness of the snack is determined by moisture content and temperature as it leaves the extruder.

Onwulata and other researchers wanted to improve the nutritional profile of puffed snack foods by extruding corn flour with concentrated forms of whey. At first, however, they found that the whey protein isolate they employed reduced the crunchiness, color and texture of extruded snack foods. By changing the temperature and moisture in the extruder, however, researchers were able to promote a better blend of whey and corn flour , and a crunchier snack, as well.

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