It doesn't hinder how it tastes in any way, but that white film that often appears on the surface of chocolate after a while looks really unappealing. Known as fat bloom, it affects even the highest quality of chocolate, and most often chocolate-covered treats. But it's only recently that researchers at Germany's Fraunhofer Institute were finally able to figure out why chocolate coatings were more prone to the effect.
The white film is called fat bloom because that's exactly what it is, fats in the chocolate — or its filling — that have risen to the surface over time. It's often mistaken for mould, or a lack of quality, so preventing it from occurring is important for companies who make and sell confections. Eliminating it altogether might be impossible, but the researchers at Fraunhofer's Institute for Process Engineering and Packaging might have found a way to minimise it.
In order to achieve a shiny finish, chocolate-coated treats are immediately chilled after passing under a waterfall of melted chocolate, which will quickly solidify and crystallise the coating. The faster the coating can solidify, the longer it takes for fats to rise to the surface and create that white film.
However, excess liquid chocolate is collected and re-used during the coating process, and the researchers discovered that the recycled chocolate had a tendency to collect extra fat from the chocolate-covered goodies it fell off. This increased fat content of the recycled liquid chocolate coating prevents it from solidifying as quickly the next time it passes through the cooling process. That in turn makes it easier for fats to bloom on the surface of the finished product.
The researchers also identified certain types of fats often used in fillings that actually contribute to a softer chocolate coating, which also make it easier for fats to bloom on the surface. So while there's no quick and instant fix to the problem, but knowing is half the battle and there are ways to avoid the trouble spots. So the next time you open a box of chocolates from two Christmases ago, it might look as shiny and delicious as the day they left the factory. [Fraunhofer]