Heat-induced changes in lactose: isomerization, degradation, Maillard browning

1995

O'Brien, J.

Milk products are among the most sensitive of foods to the effects of thermally induced non-enzymatic sugar degradation reactions. In particular, Maillard browning reactions involving lactose and milk proteins are favoured because of the high concentrations of lactose and lysine-rich proteins in many dairy products. Products of lactose isomerization, degradation and Maillard browning in milk products are useful indicators of thermal history, and a variety of analytical methods are available for their measurement. However, the interpretation of such data depends critically on a knowledge of the chemistry and thermodynamics of the reactions involved. Research over the past 20 years has helped to define more accurately the effect of a variety of factors on the rates of Maillard reactions of lactose, the most important of which are processing temperature, ph and water activity. More recently, the significance of the physical state of the food system has been highlighted. This is especially important during the processing and storage of dried products. Uncontrolled Maillard reactions may significantly compromise the nutritional value of dairy products through the destruction of essential amino acids and vitamins and by limiting the bioavailability of other amino acids. In addition, there is evidence from animal studies that dietary Maillard reaction products may have a detrimental effect on mineral homeostasis. There is some evidence that Maillard reactions in dairy products can increase the allergenicity of some milk proteins although this is an area that has yet to be studied in detail. Similarly, it has been recognized that Maillard reactions may lead to substantial changes in the functional properties of dairy proteins, some of which may have potential technological applications.

1995/BE/BE1995_0.rdf