Ever wonder why ice cream at the bottom of the carton is chewy and filled with frost? With U.S. sales in 2010 at more than $10 billion and more than 1.5 billion gallons of U.S. ice cream produced in 2011, Nestle, the world's largest food company, wants answers.
Nestle scientists are looking to nature for help in revealing exactly which mechanism within ice crystal dynamics is responsible for taking the fun and flavor away from ice cream as it ages in home freezers.
If you are now wondering about ice crystals within ice cream, it turns out that one of nature's fiercest winter events -- avalanches -- hold many answers to making tastier ice cream.
Avalanches kill more than 150 people a year around the globe -- mostly snow mobiliers, skiers and snow boarders. Imagine a massive slab of snow breaking loose from a mountainside, shattering like broken glass, moving in excess of 80 mph within five seconds, and carrying 20 football fields, 10 feet deep with snow. It's a backcountry enthusiast's worst nightmare.
So what causes avalanches? And why, exactly, would Nestle food scientists be interested in them?
Snowpacks are made up of layers of accumulated winter snow. Each layer contains ice grains constantly changing from smaller to larger crystals. Larger ice crystals are weaker because they have fewer bonds compared to smaller, more rounded crystals, which are packed snugly together (just like ice cream when it's first made and frozen).
Avalanches occur when snowstorms or rainstorms add heavy weight, causing instability within existing snowpack layers. In fact, rain in the mountains acts like a lubricant facilitating layers within a snowpack to unlock and slip-slide away.
Avalanche research over the past half-century has closely examined the life history and growth of ice crystals as influenced by temperature.
The Institute for Snow & Avalanche Research in Switzerland (SLF) at Davos uses the world's only X-ray tomography machine to time lapse study ice crystals at temperatures between 32 and minus 4 degrees Fahrenheit. Coincidentally, most home-freezer settings are maintained at the lower end of this range.
The dynamics of ice cream crystals are in many ways similar to the ever-changing ice crystals within mountain snowpacks. So it seemed very logical that Nestle scientists in Vevey, Switzerland, should partner with their SLF brethren in Davos, and that's exactly what they did.
Ice crystals grow because temperatures fluctuate. Home-freezers may be set at 0 degrees Fahrenheit but they, too, vary by a couple of degrees on either side. Or, when you take the carton out of the freezer to get a few scoops, the ice cream is exposed to room temperature for a minute or so. When this occurs ice cream slightly melts then it refreezes. When ice cream ages the ice separates from the original ingredients of cream and sugar. Over time, ice cream becomes chewy because it looses water and air, or it becomes frosty (due to crystals growing larger similar to conditions in a snowpack) and harder to scoop.
The Nestle scientists are using the non-invasive X-ray tomography to investigate the shape and size of ice crystals and air bubbles in ice cream cartons under home-freezer conditions. By identifying the main mechanism for growth of crystals within ice cream, Nestle scientists will be able to slow it down by altering their receipt, thereby making yummier ice cream that lasts longer.