In the formulation of foods, lactose is often used for the purpose of giving the product a brown color. The browning process may be caused by either carmelization or Maillard reaction.

Carmelization occurs at rather high temperatures and consists of a succession of dehydration, condensation and polymerization reactions. The final products are called melanines because of their brown color. They are mostly water insoluble. Lactose, when heated to 302°-320°F (150°-160°C), turns yellow. It turns brown at 347°F (175°C) with a characteristic odor. Carmelization is an endothermic process that demands a rather high activation energy.

The Maillard reaction occurs between a reducing sugar such as lactose, and the amino group found in proteins. This reaction starts as a condensation of the sugar with the amino group and continues through a series of rearrangements and other reactions, ending with the formation of insoluble melanines. Also as a result of this reaction, volatile aromas are generated. The Maillard reaction can occur at low temperatures and is autocatalytic. It may be accelerated by traces of iron or manganese.

Lactose provides a very good means of inducing controlled browning in foods, especially in baked goods and confectionery. In breads, lactose produces a golden brown crust that does not discolor or fade during storage. Since lactose is not fermented by bakers yeast, it remains available for Maillard and carmelization reactions during baking and storage.

Similarly, in the production of caramel-type confections, lactose produces the desirable characteristics of the product as a result of these reactions. The controlled browning of lactose protein mixtures is highly desirable for the browning of foods in microwaves, where the lower surface temperatures that occur are insufficient for the browning produced in the conventional process.

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