Isothermal study of nonenzymatic browning kinetics in spray-dried and freeze-dried systems at different relative vapor pressure environments

Abstract

Nonenzymatic browning (NEB) in freeze-dried and spray-dried lactose, trehalose, and lactose/trehalose-based food model systems containing L-lysine and D-xylose (2% w/w) as reactants was investigated at four different relative vapor pressure (RVP) (33.2%, 44.1%, 54.5%, 65.6%) environments at room temperature. Sorption isotherms of model systems were determined gravimetrically and data were modelled using the Brunauer–Emmett–Teller (BET) and Guggenheim–Anderson–deBoer (GAB) models. Glass transition, T g, was measured by DSC. Physical structure of model systems was observed by SEM. NEB was followed spectrophotometrically. Freeze-dried and spray-dried systems had different physical structures and sorption properties, but similar glass transition behavior. NEB kinetics seemed to be affected not only by the matrix composition but also by the physical properties of the materials obtained by different drying methods. Crystallization of the component sugars seemed to have direct relation to the NEB reaction. The results indicated that different physical properties of the materials by different drying methods should be considered in controlling the NEB reaction in real low-moisture food systems. Industrial relevance Nonenzymatic browning, as a model of a possibly diffusion, controlled binary reaction between amino acids and reducing sugars produces flavours and colors but may also cause detrimental changes during processing and storage of foods. The objective of this study was to determine non enzymatic browning kinetics and the effects of different drying methods on the nonenzymatic browning behaviour of food models. According to the study presented application of the results to real food systems should take into account differences in physical properties of dried, low-moisture, food systems.