Figure 5. Nonionic emulsifiers based on polyhydric hydrophilic groups.
amples, decaglycerol monostearate has an HLB of 14.5, while triglycerol tristearate has an HLB of 3.6. Intermediate species have intermediate HLB values, and any desired value may be obtained by appropriate blending. The wide range of possible compositions and HLB values make these materials versatile emulsifiers for food applications.
Sucrose has eight free hydroxyl groups that are potential sites for esterification to fatty acids. Compounds containing six or more fatty acids per sucrose molecule have been approved for use as noncaloric fat substitutes under the name Olestra; this material acts like a triglyceride fat and has no surfactant properties. Compounds containing one to three fatty acid esters (Fig. 5) act as emulsifiers and are approved for food use in that capacity (9). They are manufactured by the following steps. First, an emulsion is made of fatty acid methyl ester in a concentrated aqueous sucrose solution. The water is then removed under vacuum at elevated temperature. An alkaline catalyst is added and the temperature of the dispersion is slowly raised to 150°C under vacuum, distilling off methanol formed on transes-terification. Finally, the reaction mixture is cooled and purified. The degree of esterification is controlled by the reaction conditions, especially the sucrose to methyl ester ratio, and the final product is a mixture of esters. The HLB value of a particular product is lower (more lipophilic) as the degree of esterification increases, as would be expected.
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