Chocolate > Composition > Physical Properties

Physical Properties of Chocolate

There are a number of physical properties of chocolate that are important to both the manufacturer and the consumer.  Some of these include: melting point, water activity, and viscosity.  A more complete description of these and many other factors relevant to the making of chocolate can be found in the book “Chocolate, Cocoa, and Confectionery” by B.W. Minifie.(1)

Melting Point
The temperature that chocolate begins to melt at is a very important property because it helps define the textural properties that you experience when eating a piece of chocolate.  This melting point is determined mostly by the fat composition in the chocolate, which can come from cocoa butter and milk fat depending on the type of chocolate.  The process used to crystallize the fat when making chocolate, called tempering, is also an important factor for the melting point. 

Cocoa butters from different parts of the world will have different melting points depending on their fatty acid composition – thus the terms hard and soft cocoa butters.  Chocolate manufacturers can select and/or blend different types of cocoa butters to achieve the melt they want for their chocolate product. 

Milk fats also have their own characteristic melting points and will affect the melting characteristics of milk chocolates.

Water Activity
Chocolate is a very low moisture food.  Moisture contents of chocolate range from 0.5-1.0%.  As the moisture content in chocolate increases, the viscosity will also increase.  This has important implications to the food manufacturer. 

The low moisture levels in chocolate also make it a very stable food product at room temperature.

Viscosity
Viscosity or the flow characteristics of chocolate are measured in various ways and are important to the chocolate manufacturer.  High viscosity chocolate is difficult to pump from one part of the factory to another.  However, if the viscosity is too thin, certain molding and depositing machines will not work right.  Therefore chocolate viscosity is a physical property that is carefully monitored and tightly controlled within defined limits. 

There are several factors that affect viscosity of chocolate.  Increasing moisture and/or the particle size of the mixture will create higher viscosity.  Conversely, increasing temperature and adding emulsifiers will tend to reduce viscosity. 

 

Nutrition

 

1. Chocolate, Cocoa, and Confectionery:  Science and Technology; 3rd ed.; Chapman & Hall: New York, 1989.