Ever wondered why Swiss cheese has holes?

Emmental cheese, which is often called Swiss cheese, is changing. Traditionally, the cheese was riddled with large holes, but Swiss scientists have discovered that mass-produced versions of Emmental have fewer holes.

That's because modern manufacturing conditions are far cleaner than in the past. Andrew Moyer is a cheesemonger who has been selling traditionally-made Swiss Emmental for years.

"The joke was that it was mice chewing holes in the cheese, but it's really bacteria," he said. "When they eat lactic acid in the cheese, it gives off gas and that gas goes together in large units and forms these holes in the cheese. That's the original theory."

Now, scientists in Switzerland have expanded on that theory. Through a series of tests which compared traditional manufacturing techniques with modern ones, they found that minute hay particles left in the milk during cheese production allowed more holes to form.

Meanwhile, very sterile milk, processed in steel tanks rather than old fashioned barrels, creates cheese that has almost no holes. 

As bigger, cleaner, more efficient manufacturing techniques squeeze out older ones, Moyer said food has changed. It may look different and it will likely taste different too.

"In pasteurized milk, you kill all the bacteria and then you start introducing bacteria to make it taste like something again. Historically... a lot of the cheeses we carry are unpasteurized and you have a lot more flavour and taste to it," he said.

Unpasteurized milk is often used in products like Parmigiano Reggiano -- and it makes a striking difference in taste. In the case of Emmental, it also makes holes. 

Moyer added the recent research into Emmental's holes confirms what he's suspected for years -- that a less sanitized manufacturing process leads to tastier results.