Impact of spray-drying conditions on the particle size of microparticulated whey protein fractions

Abstract

The particle size of microparticulated whey proteins is decisive for the sensory properties and applicability of these products in foodstuffs. The impact of spray-drying conditions on the particle size of whey microparticles was studied. Solutions of 10% (w/w) whey proteins in native mixed form (ratio of α-La/β-Lg, 20:70) and isolated form were microparticulated in a scraped surface heat exchanger with a denaturation degree of 90% or higher and were dried using a lab-scale spray dryer. The effect of drying temperatures on the particle size was evaluated for the powder form as well as after reconstitution in distilled water to the original solids content, following a multilevel factorial design with variation of the inlet (180–210 °C) and outlet (75–105 °C) temperatures in the dryer. A slight increase in particle size was observed in the powders independent of the inlet and outlet drying temperatures, which was reversible after dissolution in water. Residual water content of the powder was reduced, independent of the protein composition, as the outlet temperature during drying was increased. Scanning electron microscope micrographs of the obtained powders showed spherical particles with morphological differences depending on the protein composition of the solutions. The results were validated at pilot scale using a spray dryer with centrifugal disc atomisation.