Avalanches aid ice-cream research

Avalanche experts are helping to study how ice cream's structure changes when it is stored in a household freezer. Samples of ice cream have been scanned with an X-ray machine more typically used to study the ice crystals which are key to avalanche formation. Nestle is hoping to reveal the exact conditions under which ice crystals merge and grow. When the crystals get big enough they change the texture of ice cream and alter how it feels when it is eaten. The study of ice crystal formation has been carried out with the help of scientists at the Institute for Snow and Avalanche Research in Davos, Switzerland. The X-ray tomography machine at the institute is one of the few that can take images of tiny structures at sub-zero temperatures. "Previously, we could not look inside ice cream without destroying the sample in the process," said Nestle food scientist Dr Cedric Dubois. Via the research, summarised in a paper published in the journal Soft Matter, Nestle hopes to find a way to combat the gradual degradation of taste ice cream often suffers. As with many foods, the structure of ice cream is the key to the way it tastes. 'Chewy feel' Dr Dubois said the research had revealed that the white frost of ice crystals found on ice cream forms as a result of the temperature changes it undergoes as it is transported, sold and stored. "Most home freezers are set at -18C, but the temperature doesn't remain constant," said Dr Dubois. "It fluctuates by a couple of degrees in either direction, which causes parts of the ice cream to melt and then freeze again." Time-lapse images of ice crystals only a few microns across were gathered during the study which cycled samples through a small range of temperature changes. This showed that as water froze out it formed ice crystals that affected the structure of the ice cream and made it chewy. This could also make the dessert icier, hard to scoop, and less pleasurable to eat. The study has started to reveal the "life cycle" of the crystals and the conditions which trigger some of them to merge, enlarge and significantly alter the texture of the ice cream. "We already know the growth of ice crystals in ice cream is triggered by a number of different factors," said Dr Dubois. "If we can identify the main mechanism, we can find better ways to slow it down."