Abstract:

A review. Structured self-assembled liqs. have been considered as efficient microreactors for org. and enzymic reactions. Only recently scientists learned to use food-grade cosolvents and coemulsifiers together with hydrophilic non-ionic surfactants and to construct U-type phase diagrams with large isotropic regions ranging continuously from the oil-rich corner to the water-rich corner without any phase sepn. The U-type microemulsions facilitate triggering and control of certain reactions by changing water activities. Maillard thermal degrdn. between sugars and amino acids is the main, and almost the only, chem. reaction that was studied in food-grade microemulsions. Some examples of recent studies include: Maillard processes in binary structured fluids composed of monoglycerides of fatty acids and water forming microemulsions and lyotropic liq. cryst. structures; pseudoternary and pseudoquaternary W/O microemulsions; U-type microemulsions (W/O, O/W and bicontinuous microemulsions); enzymic reactions aimed to prep. other surfactants such as sugar esters, monoglycerides and lysolecithins or triglycerides. Reactions in microreactors lead to unique new products. The reaction products and rates are controlled by the hydrophilicity/lipophilicity of the reagents (guest mols.), their molar ratios, type of oil phase, nature of surfactants and oil/surfactant ratios, nature of curvature and its elasticity (adjusted by cosolvent and coemulsifier) and by the water activity. The field is in its infancy and will need work of many more model reactions before it will be used in industrial food applications. Enzymic reactions in non-food microemulsions are common practice but only few examples of food microemulsions as enzymic microreactors were extensively studied. [on SciFinder(R)]