Rachel Lutz

Maillard Reaction between Leucine and Glucose in O/W Microemulsion Media in Comparison to Aqueous Solution

The Maillard reaction is controlled by temperature, pH, reactant nature (sugars and amino acids), and water activity. We carried out reactions between glucose and leucine in U‐type nonionic microemulsions to obtain regioselectivity and control reaction rates. Reactants were oriented at the interface and water activity was adjusted using blends of surfactant and propylene glycol (PG). U‐type microemulsions, previously studied by us, served as microreactors for the Maillard reaction. The reactions in the microemulsion media were slower than those carried out in aqueous solution and formed unique aroma compounds. Reaction rates increased when using systems richer in water, as the water activity was enhanced. The surfactant plays a key role in determining water activity and reagent reactivity in all the microemulsions. The presence of PG slows the reaction, mainly when it resides at the interface, facilitating the formation of a bicontinuous structure. Phase transitions within the U‐type microemulsions were determined by viscosity and SD‐NMR and were correlated to the interfacial presence of the reactants and their reactivity.

A Study of the Emulsified Microemulsion by SAXS, Cryo‐TEM, SD‐NMR, and Electrical Conductivity

A water‐in‐oil microemulsion was further dispersed in an aqueous phase containing Pluronic F127 as a steric stabilizer, to form a specific type of double emulsion termed emulsified microemulsion (EME). The inner microemulsion phase was made from glycerol‐monooleate (GMO), R(+)‐limonene, ethanol and glycerol. SAXS (small x‐ray scattering), PGSE‐NMR (pulse gradient spin echo‐NMR), electrical conductivity, and cryo‐TEM (cryogenic‐transmission electron microscopy) imaging techniques were used to confirm the existence of inner W/O nano‐droplets after second emulsification step and upon EME aging. Spherical globules of EME without long‐range internal order were observed by the SAXS measurements and the cryo‐TEM images. The average globule size of about 200–300 nm remained intact for at least 6 months.