Synthetic Emulsifiers

Mono- and Diglycerides of Fatty Acids

The most commonly used emulsifiers in the food industry are mono- (MG) and diglycerides (DG). These are prepared commercially by direct esterification of edible fats or fatty acids (from vegetable or animal origin) with glycerol at elevated temperatures, or by interesterification of an oil with glycerol.483 During transesterifica-tion, triglycerides are heated with glycerol and a catalyst, usually sodium hydroxide, under vacuum at 200°C. As the fatty acids are hydrolyzed from the triglycerides, some re-esterify at other free hydroxyl positions to form mono- and diglycerides.84 The yield of MG depends on the proportion of triglyceride to glycerol used. Such methods were demonstrated by reacting the oils of coconut, peanut, sesame, linseed, and sardine and direct esterification of fatty acids with glycerol.85 Feuge and Bailey86 demonstrated that the proportions of glycerol, mono-, di-, and triglycerides can be calculated statistically based on two assumptions: The reaction between admixtures from either method contains traces of free glycerol and free fatty acids, which can be removed by distillation. Commercial MG usually contain about 40 to 50% monester, 40% diester, and 10% triglycerides.87

Mono- and diglycerides of fatty acids exist in several structural modifications (Figure 7.4). In monoglycerides, if the fatty acid is attached to the middle carbon atom, the molecule is symmetrical and the monoglyceride can be termed a beta-monoglyceride. When the reaction is carried out at 20°C the relative proportions of o ch2-oV I o

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