06/12/2001

Chow Line on Swiss cheese for 7/1/01

Writer:

Martha Filipic
filipic.3@osu.edu
(614)292-9833

Source:

James Harper

Mike Mangino

Swiss cheese holes stem from bacteria

Why does Swiss cheese have holes?

That's easy. The culprit is (let's say it all together now) Propionibacter shermani.

All cheese is made with the help of bacteria, or more specifically, a bacteria-based culture. These "starter organisms" are added to milk and are one of the major factors that help determine the type of cheese that you end up with.

For Swiss cheese, S. thermophilus and Lactobacillus start the process, producing acid and using lactose from milk as an energy source. Then the mixture is placed in a warm room, which favors the growth of P. shermanii. That uses the lactic acid to produce carbon dioxide and propionic acid. Carbon dioxide makes the holes by expanding into bubbles of gas, and propionic acid helps produce Swiss cheese's characteristic flavor.

The size of the holes can be controlled by varying several factors: acidity, temperature and curing time. Because of this, food scientists say cheese-making is a combination of art and science. It takes a certain expertise to get conditions "just right."

Knowing how to control hole-size is important: Until recently, the holes in Grade-A Swiss cheese had to be between eleven-sixteenths and thirteen-sixteenths of an inch in diameter (that's almost precisely three-quarters of an inch, about the size of a nickel). However, standards are changing: Modern processing equipment, designed to slice cheese at a rate of 1,000 slices a minute, often tears up large-hole Swiss cheese. That prompted regulators to re-think the strict standard. Now Swiss-cheese-holes can be as small as six-sixteenths (that's three-eighths) of an inch and still be classified as Grade-A. All processors have to do is refrigerate the cheese sooner, stopping the bubbles from getting too large before they burst.

Baby Swiss cheese is made from the same type of bacterial culture, but cheese-makers adjust the curing process (acidity, temperature and time) to end up with a milder cheese with smaller holes.

Ohio is the nation's top producer of Swiss cheese, making about 64 million pounds annually. An ounce of Swiss cheese contains about 8 grams of fat, a little over 100 calories, and about 275 milligrams of calcium. And, if you want to sound like you know a thing or two, the holes in Swiss cheese are properly called "eyes."

Chow Line is a service of The Ohio State University. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH 43210-1044, or filipic.3@osu.edu.