Why is roller/drum dried milk powder better than the alternatives?
Roller whole milk is desired by chocolate manufacturers for its high free fat content, which provides superior viscosity reduction and requires 2-3% less cocoa butter to maintain the handling properties during manufacture. The result is a milk chocolate product with a desirable mouth feel.
In addition to a high free fat content, manufacturers prefer roller/drum dried milk powder because of the sought-after taste it contributes to chocolate. The intense heating of the roller process begins the Maillard reaction, creating a pleasant cooked and caramelized flavor. This unique flavor profile offers characteristics unobtainable from other sources of milk powders.
Free Fat
Nearly all the milk fat in roller-processed milk powder is "free". Because of this, roller-processed whole milk provides superior viscosity reduction. In spray-processed whole milk, much of the milk fat is bound and does not interact freely.
There are several factors that impact the degree of free fat in a milk powder, with the processing conditions being key to developing a powder with high free fat. Roller-dried has a characteristically high free fat level (70-90%) due to the shearing and scraping action as the film dries on the drum surface. Because of this, roller-dried is ideal for use in milk chocolate. Spray dried milk powder has significantly lower free fat levels (2-3%). In spray dried whole milk the milk fat is largely absorbed inside the lactose-protein structure of the dried milk particle.
One concern with powders containing a high free fat content is that fat oxidation leads to the development of off-flavor and a shorter shelf life. This situation is less of a concern for roller-dried powder where it is believed that maillard reaction products provide some anti-oxidant effects and hence enable storage lives of up to 12 months to be achieved without inert gas packaging.
Maillard reaction
The maillard reaction describes a complex series of reactions between reducing sugars and amino groups on proteins, peptides and amino acids. The net effect of these reactions is the generation of colorful and flavorful compounds. Confectionery manufacturers prefer more intense caramel and Toffee flavors to assist in the flavoring of the confectionery product. Thus, for the manufacturer of confectionery ingredients, optimizing the level of maillard reaction can be beneficial. These complex chemical reactions are strongly influenced by the temperature and the duration of heating, the water content, the PH, and the ratio of reactants. The reactions take place in the roller-drying process of milk powder and in the chocolate crumb process.