Chemical Changes in Spray-Dried Skimmilk Held Near Dryer Outlet Temperatures

Abstract

The hydroxymethylfurfural (HMF) content and fluorescence of spray-dried powders (2.8 to 5.6% H20) made from pasteurized skimmilk increased during storage at temperatures similar to those encountered in products held in bulk storage without cooling immediately after drying (37 to 60 C). Rate of increase was directly-related to the storage at 50 C, an increase of HMF in powders containing 2.8% H2O could be detected, the amount originally present doubling during 16 hours of storage. The powders exhibited changes in the pattern of fluorescence excited by ultraviolet light having wavelengths of 330, 360, and 390 mµ. More than a fivefold increase in HMF and a doubling of fluorescence activated at 330 mµ was observed before changes in the visible color of the powder became detectable. Since no significant changes were noted in the powders during one week of storage at 37 C, it was concluded that chemical changes in milk constituents during spray drying can be further decreased by cooling powder to this temperature immediately after drying. © 1968, American Dairy Science Association. All rights reserved.