Physical Properties of Concentrated Milk and Its Influence on Powder Milk Characteristics and Spray Dryer Design Parameters

The present work analyzed the properties of two concentrated milks, as well as the influence of the reconstituted type on some properties of milk powder. Two sets of milk with high solids content (43–60% w/w) were employed; one set was concentrated by evaporation of liquid milk, while the other was prepared by reconstitution of milk powder. Both concentrated milks were characterized at the different solids contents, measuring flow and physicochemical properties; finding a non‐Newtonian behavior well fitted by the Power law model. The bh color parameter, density and consistency coefficient increased, while luminosity, redness and flow index decreased as a function of solids concentration. Lately, the reconstituted milk with four levels of concentration was spray dried, and their properties, such as apparent density, color, moisture, particle size and rehydration, were determined. Based on properties of reconstituted and powder milks, other engineering parameters, such as drop diameter and heat transfer coefficient, were equated, in order to relate physical properties for dryer design. PRACTICAL APPLICATIONS This work is not a sophisticated study. It covers the fundamentals and practical aspects of a very important food process operation, drying of milk. Most of the works on food preservation methods have been conducted to analyze microbiological, physicochemical and processing aspects, and very few studies have been carried out to analyze the transport phenomena in spray drying, passing by concentration aspects and properties. Thus, this practical and useful work applies momentum, heat and mass transfer approaches to quantify the flow properties of two concentrates and how they influence some physical properties for milk powder and two design parameters for the dryer performance.