When chocolate is first made, and then again when it is melted and reshaped, it needs to be tempered in order to retain its glossy structure and consistency. This means that the crystals are restructured in a precise way by controlled cooling.
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Tempering in metallurgy refers to heating and cooling a metal, normally steel, to improve properties such as consistency, durability or hardness. The same is true for chocolate. [Bristol chocolatier Zara] Narracott passes me an untempered piece for tasting: it has a white coating and looks dry. Once in the mouth, it instantly crumbles rather than melts, but still tastes good. Next up is an extremely smooth and glossy-looking dark chocolate with a caramel centre. Biting into it gives a very satisfying crunch allowing the caramel to ooze out. Delicious.
Cocoa butter – the fat obtained from cocoa beans and mainly consisting of oleic, palmitic and stearic fatty acids – gives chocolate its physical structure. When tempering chocolate, it is the crystal structure of the cocoa butter that chocolatiers are manipulating. ‘Cocoa butter is a six-phase polymorphic crystal,’ explains chocolatier Richard Tango-Lowy, a physics graduate who now runs the Dancing Lion Chocolate shop in Manchester, US. The desirable crystal structure for chocolate is form V.
A dive into the crystallization of chocolate can help us understand why factories with their chemists and experienced chocolatiers produce a consistently better product than a home cook, but there are ways that anyone can learn to temper chocolate with practice. The science underneath the art of chocolate is explained at Chemistry World. -via Metafilter
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