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Polymorphs of Chocolate – Why Chocolate needs to be Tempered?

01-10-2019 | Author : Inchara Govind

Polymorphs of Chocolate – Why Chocolate needs to be Tempered?

Cocoa butter is the primary ingredient in chocolate, which is composed mainly of fat molecules. It is the arrangement of these fat molecules that determines the structure of chocolate.

Cocoa butter has six crystal forms. The ability of a substance to display different structures is called polymorphism. These crystals differ in how the fat molecules are arranged, which influences their properties like appearance, taste and texture and therefore affect the taste and quality of the chocolate.

The most desired chocolate form is form V; it has a shiny appearance and produces the desirable audible snap when broken, melts in the mouth and has a smooth texture. Unfortunately, it is not a very stable form.

If melted cocoa butter is allowed to cool naturally, a mixture of forms I – V will be formed. This isn’t ideal as forms I – IV have less desirable properties.

Tempering chocolate involves cooling the melted chocolate at a very slow rate in order to increase the amount of form V crystals formed. Once cooled, the chocolate is heated again to a temperature lower than the melting point of form V, and higher than that of forms I-IV, causing the forms I-IV to melt.

Polymorphs of Chocolate

Forms Melting Point (Celsius)
Form I – beta-prime 2 17.3
Form II – alpha 23.3
Form III – mixed 25.5
Form IV – beta-prime 1 27.3
Form V – beta 2 33.8
Form VI – beta 1 36.3

Form VI doesn’t form when melted chocolate solidifies. It only forms after several months when the fat molecules have enough energy to form it. This is when fat bloom occurs on the chocolate due to partial melting causing the fat molecules to rise to the surface. This can be stopped by storing the chocolate in the refrigerator i.e. at a lower temperature so that the fat molecules don’t obtain enough energy.

Therefore, to answer the question, why chocolate needs to be tempered – It is the cocoa butter in the chocolate which needs to be tempered in order to achieve the most desirable form of crystals; Form V.