Theory: Eutectics

For confectioners, a eutectic is a mixture of fats with a lowered melting point: the softening effect of the combined fats is more pronounced than would be predicted from simply combining the two and averaging their melting points. When combined with cocoa butter, many fats and oils create eutectics. The butterfat in milk chocolate forms a eutectic with cocoa butter that makes milk chocolate softer than dark chocolate and causes it to have a lower working temperature. The nut oil present in gianduja has the same effects on cocoa butter. One of the most pronounced examples of a eutectic effect comes from the combination of coconut fat or palm-kernel fat with cocoa butter. Both coconut and palm-kernel fats are tropical fats; a more accurate term is lauric fats, named for their chemical makeup. When a lauric fat is combined with cocoa butter, the eutectic effect is dramatic. When coconut fat with a 33°C/92°F melting point is combined with cocoa butter, which melts at around 34°C/93°F, the resulting mixture melts well below the temperature of either of the component fats, with the exact melting temperature dependent on the ratio of fats. Confectioners take advantage of this phenomenon to create centers called meltaways. The resulting compound fat melts quickly when these products contact the palate, spreading the flavor and releasing the aromatics of the center. Often meltaways are combined with nut pastes to rapidly release the nut flavor. With these products, the transition from a solid to a liquid state happens so quickly that it is possible to feel the heat being absorbed from the mouth. This is the reason that centers of this description actually leave a cool feeling on the palate as they rapidly melt.