Sucrose ester microemulsions as microreactors for model Maillard reaction

Thermal reactions of cysteine/furfural mixture were studied as a model syst em to gain more insight into the influence of structured fluids such as wat er-in-oil nonionic microemulsions on the generation of aroma compounds. The microemulsion systems were composed of: sucrose ester/water/dodecane + alc ohol(1/1), where the sucrose esters are sucrose stearate (S1570) and sucros e laurate (L1695), and the alcohols are medium-chain alcohols (C2OH to C6OH ). Formation of predominately 2-furfurylthiol (FFT) is obtained in the aque ous cysteine/furfural system. The formation of FFT was enhanced under simil ar reaction conditions in water-in-oil microemulsions and led to the format ion of two new sulfur compounds that were identified as 2-(2-furyl)-thiazol idine and tentatively N-(2-mercaptovinyl)-2-(2-furanyl)-thiazolidine. The r eaction rates (furfural conversion or consumption) decrease with the decrea se in the water content and the increase in alcohol chain length (C-2 to C- 6 were used as cosurfactant) and with the increase of pH from 4 to 8 in the system containing butanol as the alcohol. The rates of reaction increase a lso with the increase of temperature in the range of temperatures studied f rom 30 to 60 degreesC. The kinetic constants (k) and energy of activation ( Ea) were calculated. Microemulsions of W/O are excellent reaction media for the Maillard reactio n providing a high selectivity, high conversion rates and specificity. (C) 2001 Elsevier Science B.V. All rights reserved.