Color formation in dehydrated modified whey powder systems as affected by compression and Tg

Whey powders have attracted attention for use in the food industry. The Mai llard reaction is a major deteriorative factor in the storage of these and other dairy food products. The objective of the present work was to further study the Maillard reaction as related to the physical structure of the ma trix, either porous or mechanically compressed, or to storage above the T-g of anhydrous whey systems. Sweet whey (W), reduced minerals whey (WRM) whe y protein isolate (WPI), and whey protein concentrate (WPC) were stored in ovens at selected temperatures. Colorimetric measurements were performed wi th a spectrocolorimeter, thermal analyses (TGA) by means of a thermobalance , and glass transition temperature studies by DSC. The browning order in th e vials and in the compressed systems followed the order W > WRM > WPC > WP I. k(w2), the slope of the second linear segment of the TGA curve, was rela ted to the loss of water due to nonenzymatic browning (NEB). Browning devel opment was in good relationship with this loss of weight. In the glassy sta te, the compressed systems developed higher rates of browning and weight lo ss (assigned to NEB reactions) than the porous systems. Reaction rates in b oth (porous and compressed) systems became similar as (T - T-g) increased.