Nonenzymatic Browning in Food Models in the Vicinity of the Glass Transition:  Effects of Fructose, Glucose, and Xylose as Reducing Sugar

Abstract

Effects of a reducing sugar, fructose, glucose, or xylose, and glass transition on the nonenzymatic browning (NEB) rate in maltodextrin (MD), poly(vinylpyrrolidone) (PVP), and water systems were studied. Glass transition temperatures (T(g)) were determined using DSC. Water contents were determined gravimetrically, and NEB rates were followed at several temperatures spectrophotometrically at 280 and 420 nm. Reducing sugar did not affect water contents, but xylose reduced the T(g) of the solid models. Sugars showed decreasing NEB reactivity in the order xylose > fructose > glucose in every matrix material. The NEB reactivity and temperature dependence of the single sugars varied in different matrices. The NEB rates of the solid models increased at temperatures 10-20 degrees C above the T(g), and nonlinearity was observed in Arrhenius plots in the vicinity of T(g). The temperature dependence of nonenzymatic browning could also be modeled using the WLF equation.

Maillard Reaction Rate in Various Glassy Matrices

“…21) Thus, in this study, k 280 obtained by the pseudo zero order reaction formula of ÁOD 280 was treated experimentally as a MR rate in accordance with the previous studies. [16][17][18]21) Moreover, the temperature dependence of k 280 was described well by the Arrhenius formula in the temper- The T g of sample was investigated by DSC, and the heating curve of every sample is shown. The arrows show the T g .…”

“…The freeze-dried sample was stored at 10 C intervals at temperatures between 40 C and 70 C. After storage, the sample was rehydrated to 0.04 sample-g/ml with distillated water, and the extent of MR was estimated spectrophotometrically (Shimadzu UV-160) by optical density at 280 nm (OD 280 ). OD 280 , which is considered to be due to the formulation of furfural compounds, is often used to detect the early stage of MR. [16][17][18]21,22) Similarly, optical density at 420 nm, which quantifies the yellow and browning pigments formed at the final stage of MR, is also used, but only OD 280 , which can detect even slight progress in MR, was used in this study. For the average of the three measurements, the difference in OD 280 before and after storage (ÁOD 280 ) was estimated as the extent of MR during storage.…”

“…Since molecular mobility usually affects the rate of physical change or chemical reaction, it is believed that the T g value of glassy food is a critical factor for the consideration of storage stability. Actually, it has been reported that the rate of some undesirable physical changes (e.g., crystallization, 10,11) and structural collapse 12) ) or chemical reactions (e.g., degradation, 13) oxidation, 14) and MR [15][16][17][18][19][20] ) have a close relation with T g . That is, the rates below T g are much slower than that above T g .…”

Mechanisms of protein stabilization in the solid state

“…55 Reducing sugars include fructose, maltose, lactose, glucose and xylose, and the reactivity for each sugar is different. 62 Even though sucrose is a nonreducing sugar, it is possible for it to hydrolyzed into reducing sugars, especially at low pHs. 63 The Millard reaction can lead to the formation of brown, fluorescent advanced glycation end products, and crosslinking of proteins, which have received considerable attention in recent years in both food and health sciences.…”

Protein quality of pig diets : processing effects on amino acid digestibility and post-absorptive utilization

“…Xylose has the highest non-enzymatic browning (Maillard reaction) activity (Lievonen et al, 2002). The highly reactive free ε-amino group of Lys is mostly involved in the Maillard reaction followed by Arg ).…”