Another milestone in the quest for the perfect pizza: Cornell University researchers have discovered how to make fat-free or low-fat mozzarella cheese melt better.

As a result the future promises pizza with low-fat cheese that not only tastes better but also looks as good as regular cheese. The secret: "You don't need a lot of fat inside the cheese, you just need a very small amount of fat on the surface," says Michael Rudan, Cornell postdoctorate researcher in food science. "We think we've found the key to making low-fat mozzarella cheese melt right."

Of course, there are sound reasons for this discovery, particularly nutritionists' concern about the high level of fat in the American diet. And of the 2.25 billion pounds of mozzarella cheese being made each year in the United States, about 75 percent of it is destined for a pizza. Although mozzarella cheese manufacturers are making strides toward developing a good-tasting, lower-fat product, the no-fat or low-fat mozzarellas don't melt or fuse together well during baking. They also brown and scorch excessively, which is hardly appetizing for pizza lovers.

In their quest for perfection, Cornell food scientists at the Northeast Dairy Foods Research Center found that applying a thin hydrophobic surface coating with an oil-spray product to the cheese before baking makes the no-fat and low-fat mozzarella behave like its full-fat cousin by fusing, browning and blistering.

Makers of fresh, refrigerated and frozen pizza might be able to use this spray-on surface coating -- an invisible glaze of a half-gram of canola oil per 100 grams of cheese -- to make their products look as if they contain higher-fat cheese.

Rudan's effort in the cause of healthier pizza has been recognized by his peers. In May he received the national Alltech Inc. Graduate Student Publication Award from the American Dairy Science Association for a paper titled "A Model of Mozzarella Cheese Melting and Browning During Pizza Baking." Rudan is a native of Ithaca, graduating from Ithaca High School in 1980, and he earned his bachelor's, master's and doctoral degrees all from Cornell.

But Rudan is not a one-cheese problem-solver. Other low-fat cheeses, particularly processed and single-wrapper products, form a skin when heated, making the cheese unappetizing to consumers of toasted cheese sandwiches or burgers. But Rudan found that coating the cheese with a hydrophobic surface prevents the formation of a skin, giving the cheese better flow and melt characteristics.

Says Rudan, who works in Cornell food science Professor David Barbano's laboratory: "In our thinking, this was a breakthrough about food. We showed it was the fat on the surface of the cheese shred that plays a key role in melting. Before, no one really understood those properties. We didn't really understand why regular mozzarella cheese was melting like it did."