Healthy pizza cheese for school lunch programs

Dairy Foods, Sept, 1994

Whether it's dine-in, pick-up or delivery, one common denominator exists in pizza: fat.

No matter how you slice it, Americans consume approximately 100 acres of pizza each day. And, nutritionists estimate that the average fat content in pizza hovers somewhere near 5%, with the main culprit coming from that delicious stringy topping known as mozzarella cheese.

There might seem to be an easy answer to the problem, given that several brands of low-fat mozzarella are now on the market. But many consumers find current low-fat mozzarella unacceptable and many pizzerias aren't ready to trade the cheesy quality of their full-fat products for a minimal fat reduction gained by using low-fat mozzarella cheese.

But, scientists with the Agricultural Research Service (ARS) at USDA are addressing this dilemma without trading off the melting and texture qualities for reduced fat.

"We've developed a type of mozzarella containing only 10% fat by weight with melting and textural properties similar to those of commercial full-fat mozzarella," says Edyth Malin, research chemist, ARS' Eastern region research center, Philadelphia. "It's a significant development, considering that full-fa mozzarella contains about 22% fat and part-skim typically has 17% fat."

USDA's Food and Nutrition Service is evaluating the ARS-developed low-fat mozzarella for possible inclusion in the National School Lunch Program. Developed at the Philadelphia center's Dairy Products Research Unit, the technology is helping solve a dilemma many parents and school cafeteria officials currently face: offering children dairy products rich in calcium and protein, while offsetting fat.

School children currently consume pizza topped with cheese containing about 20% fat, resulting in 55% of calories from fat, according to Malin. Dietary guidelines call for less than 30% of calories from fat in a meal. Pizza account for the major source of fat when it is served in school lunches.

"New low-fat products like this are important as we work to provide children with appealing meals that comply with the Dietary Guidelines for Americans," says Ellen Haas, USDA assistant secretary for Food and Consumer Services. "Common sense tells us that when the market learns that we (USDA) want to buy low-fat mozzarella, there will plenty of low-fat mozzarella to buy,"

Process modifications

Research chemist Michael Tunick explains that ARS mozzarella is produced using normal cheesemaking procedures, equipment and cooking time. However, the researchers have reduced cooking temperatures from 100 [degrees] F to 90-99 [degrees] F.

"Lower temperatures and the resulting higher moisture content increase the survival of rennet, the enzyme added to milk to clot the proteins into curd," Malin says. "As a result, a larger number of enzymes can go to work breaking down milk proteins into smaller peptides.

"Increased breakdown of milk proteins results in a softer cheese with the texture and melting characteristics of full-fat mozzarella," Malin adds.

The scientists also found that refrigerating the low-fat mozzarella at 40 [degrees] F for up to six weeks after cheesemaking enhances meltability. "This is because the breakdown of milk proteins by enzymes and starter culture bacteria continues during storage," Tunick explains.

"This development is good news for health-conscious consumers and the pizza industry. Most of the 1.8 billion lbs. of mozzarella consumed enter the market at the wholesale level for use by food processors and restaurants in the manufacture of pizza."

Malin uses molecular modeling to study the texture characteristics of the low-fat mozzarella. These three-dimensional views of molecules allow ARS scientists to simulate proteolysis of milk proteins to peptides. Peptides break up the dense protein body of cheese, improving texture and meltability.

Patented technology

A patent application has been filed on modifications to the technology develope by Malin and co-inventors Tunick, Virginia Holsinger and Phillip Smith at the Philadelphia center, and is available for license by the industry.

The scientists found that when homogenized milk was used to prepare full-fat mozzarella, there was a reduction in the amount of oil normally formed when cheese is heated. "Mozzarella typically used on pizza contains 22 to 25% fat, but when it's heated in an oven, about half of the fat oils off," says Tunick.

To solve that problem, the inventors adjusted the amount of pressure used in homogenization. "Reducing the size of the fat particles results in less than 5% oiling off," Tunick says. "Homogenization of the milk reduces the size of the fat globules, resulting in greater emulsification, and causes the fat to be enclosed by the protein. This effect also enables more fat to be retained durin the cheesemaking process."