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Nonenzymatic Browning in Amorphous Food Models: Effects of Glass Transition and Water Texto completo
2002
Lievonen, S.M. | Roos, Y.H.
The effect of glass transition on nonenzymatic browning (NEB) rates of amorphous, L-lysine, and D-xylose containing maltodextrin (MD)- or polyvinylpyrrolidone (PVP)-based food models, equilibrated into a(w) of 0.23, 0.33, or 0.44 was studied. Glass transition temperature, T(g), was measured using DSC and NEB rates, followed spectrophotometrically. Use of citrate buffer as a pH regulator was evaluated. The NEB rates were higher in PVP than in MD models. Arrhenius plots showed nonlinearity in the vicinity of the T(g). Increasing a(w) decreased T(g), but did not affect NEB rates around the T(g). The temperature difference (T - T(g)) was not a sufficient measure of material stability.
Mostrar más [+] Menos [-]Furfural-cysteine model reaction in food grade nonionic oil/water microemulsions for selective flavor formation Texto completo
2002
Yaghmur, A. | Aserin, A. | Garti, N.
The thermal reaction between cysteine and furfural was investigated at 65 degrees C in five-component food grade oil/water (O/W) microemulsions of R-(+)-limonene/ethanol, EtOH/water/propylene glycol, PG/Tween 60 as apart of a systematic study on the generation of aroma compounds by utilizing structured W/O and O/W fluids. The furfural-cysteine reaction led to the formation of unique aroma compounds such as 2-furfurylthiol (FFT), 2-(2-furanyl)thiazolidine (main reaction product), 2-(2-furanyl)-thiazoline, and N-(2-mercaptovinyl)-2-(2-furanyl)thiazolidine. These products were determined and characterized by GC-MS. Enhancement in flavor formation is termed "microemulsion catalysis". The chemical reaction occurs preferably at the interfacial film, and therefore a pseudophase model was assumed to explain the enhanced flavor formation. The product internal composition is dictated by process conditions such as temperature, time, pH, and mainly the nature of the interface. Increasing water/PG ratio leads to a dramatic increase in the initial reaction rate (V0). V0 increased linearly as a function of the aqueous phase content, which could be due to the increase in the interfacial concentration of furfural. Microemulsions offer a new reaction medium to produce selective aroma compounds and to optimize their formation.
Mostrar más [+] Menos [-]Non enzymatic browning in a complex food according to time, water activity, pH and temperature
1994
Clotet, R. (Escola Superior de Barcelona (Espagne). Departimento d'Industries Agro Alimentaries, Bioquimica) | Erruz, E. | Valero, J.
