Color Formation in Dehydrated Modified Whey Powder Systems As Affected by Compression andT_g

Abstract

Whey powders have attracted attention for use in the food industry. The Maillard 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 matrix, either porous or mechanically compressed, or to storage above the T(g) of anhydrous whey systems. Sweet whey (W), reduced minerals whey (WRM), whey protein isolate (WPI), and whey protein concentrate (WPC) were stored in ovens at selected temperatures. Colorimetric measurements were performed with a spectrocolorimeter, thermal analyses (TGA) by means of a thermobalance, and glass transition temperature studies by DSC. The browning order in the vials and in the compressed systems followed the order W > WRM> WPC > WPI. k(w2), the slope of the second linear segment of the TGA curve, was related to the loss of water due to nonenzymatic browning (NEB). Browning development was in good relationship with this loss of weight. In the glassy state, the compressed systems developed higher rates of browning and weight loss (assigned to NEB reactions) than the porous systems. Reaction rates in both (porous and compressed) systems became similar as (T - T(g)) increased.

Lactose crystallisation and early Maillard reaction in skim milk powder and whey protein concentrates

“…However, the progress of EMR is also dependent on the protein/lactose ratio initially present in WPC: WPC35 (with 35% protein and 51% lactose) reacted faster than WPC60 (with 60% protein and 23% lactose). These results were in accordance with the study by Burin et al [2], where the rate of Maillard browning followed the order sweet whey powders > WPC > whey protein isolate. This was related to the differences in the content of lactose in these powders.…”

“…This could be due to a limiting number of free lactose molecules available for each protein monomer in low-lactose WPCs. The importance of the composition of whey systems on the rate of Maillard reaction has been previously highlighted by Burin et al [2]. Moreover, the Tg/a w relationship slightly differs according to the protein/lactose contents in WPCs (unpublished data).…”

“…The understanding of the physical behaviour of milk powders has markedly increased during recent years, and useful tools such as the milk state diagram have been developed [8,11,19]. The link between physical state and Maillard browning (which does not account for EMR only) has been demonstrated in various dehydrated model systems [9,12], milk powders [16,19] and whey powders [2,10,17]. Numerous authors have shown that the crystallisation of amorphous lactose in dairy and whey powders is controlled by the temperature difference between storage temperature and glass transition temperature (Tg).…”

“…Jouppila and Roos [7] have observed on milk powders that lactose crystallisation was affected by the presence of milk proteins (when compared with pure lactose). Burin et al [2] have shown that besides physical parameters, the composition of whey models plays a role in their propensity to undergo Maillard reactions. Recent data have been focused on the role of protein content and structure on the crystallisation of lactose in amorphous materials.…”

State diagrams for improving processing and storage of foods, biological materials, and pharmaceuticals (IUPAC Technical Report)

“…The increase in water content resulting from the Maillard reaction is reflected in a depression of T g [73,121]. Water is also released as a consequence of crystallization of certain amorphous sugars, and both accelerated enzyme inactivation and browning development can result [122,123]. The magnitude of that effect was dependent on the degree of matrix collapse or porosity, which affected water retention in those systems [61,121].…”