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The Maillard Reaction Application to Confectionery Products
C.G.A. Davies & T.P. Labuza Department of Food Science and Nutrition University of Minnesota, St. Paul, Minnesota 55108

2 Introduction The reaction between sugars and amino groups was first described in 1908 by two Englishmen, Ling & Malting, who considered color formation in beer. In 1912 LouisCamille Maillard described a browningreaction between reducing sugars and amino groups. Despite not being the first to report the reaction, Maillard was the first to realize the significance of the reaction in areas as diverse as plant pathology, geology and medicine. It is interesting to note that despite there having been six international symposium on the Maillard reaction, not one of the papers was a direct study on the Maillardreaction in confectionery (e.g. Waller & Feather, 1983; Finot et al., 1990, Labuza et al., 1994). In fact, it seems that recent symposia were as much concerned with the medical aspects as food chemistry of the Maillard reaction. The medical world has begun to realize that there may be a role for the Maillard reaction in the formation of complications of diabetes and aging, in which the bloodglucose becomes bound to proteins in the body in a similar way to food proteins and glucose. Despite the lack of direct research on the Maillard reaction in confectionery, it can be seen that the Maillard reaction will play an important role in the formation of flavors and colors of some confectionery products since the main Maillard reactants are present. This paper is particularly concerned with theMaillard reaction in non-chocolate confectionery. Non-enzymatic browning reactions pathways The Maillard reaction is one of four nonenzymatic browning reactions which occur in food. The other three are: 1) the degradation of ascorbic acid, 2) lipid peroxidation 3) sugar-sugar caramelization. The chemistry of these reactions is related to the Maillard reaction. Ascorbic acid (AsA) undergoes areaction chemically similar to that of sugars except that amino acids are not necessary for browning. Since AsA is very reactive, it degrades by two pathways, both of which lead to the formation of dicarbonyl intermediates and subsequently to form browning compounds (Davies & Wedzicha, 1992). Lipid peroxidation occurs by the action of oxygen and reactive oxygen species on the fatty acids, especiallyunsaturated fatty acids. These are oxidized to form aldehydes

3 and ketones which then react with amino acids to form brown pigments, as in the Maillard reaction. It is possible that peroxidation products induce the browning reaction of the Amadori products (Hermosin et al., 1992). At high temperatures (> 80 oC) sugar-sugar interactions or the caramelization reaction occurs. This is a complexseries of reactions but many of the intermediate flavor compounds and products are similar to those observed for the Maillard reaction. Mechanism of the Maillard reaction The chemistry of the Maillard reaction is known as a complex series of reactions leading to the formation of a variety of products, including the flavors, aromas and colors MAILLARD BROWNING PATHWAY considered important in foodscience today. The classical scheme of the chemical reaction is that of Hodge as shown in Figure 1 (Hodge, 1953) This is still used today to describe the reaction. The Maillard reaction was first described as between reducing sugars with amino acids, but now is extended to include many other carbohydrate and amine groups. Sugar sources include dextrose, fructose, high fructose corn syrup, sucrose,corn starches and maltodextrins. Protein (-NH2) sources for candy may include milk solids, cream, egg solids, nuts and nut fragments, cocoa solids, butter (small source of nitrogen), fruits and fruit juices provide free amino MELANOIDINS acids, gelatin, whey proteins and (BROWN NITROGENOUS POLYMERS AND COPOLYMERS emulsifiers such as lecithin. Figure 1. Modified Hodge scheme for nonenzymatic...
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