Improved flowability and wettability of whey protein-fortified skim milk powder via fluidized bed agglomeration

Chan Won Seo 1 , *
Author Information & Copyright
1R&D center, Seoul Dairy Cooperative, Ansan 15407, Korea.
*Corresponding Author: Chan Won Seo, R&D center, Seoul Dairy Cooperative, Ansan 15407, Korea. E-mail:

© Copyright 2022 Korean Society for Food Science of Animal Resources. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Jul 18, 2022 ; Revised: Aug 03, 2022 ; Accepted: Aug 16, 2022

Published Online: Aug 16, 2022


Recently, protein-fortified milk powders are being widely consumed in Korea to prevent sarcopenia, and the demand for high-protein food powders is continuously increasing in the Korean market. However, spray-dried milk proteins have poor flowability and wettability owing to their fine particle sizes and high inter-particle cohesive forces. Fluidized bed agglomeration is widely used to improve the instant properties of food powders. This study investigated the effect of fluidized bed agglomeration on whey protein isolate (WPI)-fortified skim milk powder (SMP) at different SMP/WPI ratios. The fluidized bed process increased the particle size distribution, and agglomerated particles with grape-like structures were observed in the SEM images. As the size increased, the Carr index (CI) and Hausner ratio (HR) values of the agglomerated WPI-fortified SMP particles exhibited excellent flowability (CI: <15) and low cohesiveness (HR: <1.2). In addition, agglomerated WPI-fortified SMP particles exhibited the faster wetting time than the instant criterion (<20 s). As a result, the rheological and physical properties of the WPI-fortified SMP particles were effectively improved by fluidized bed agglomeration. However, the fluidized bed agglomeration process led to a slight change in the color properties. The L* (lightness) value decreased, and the b* (yellowness) value increased because of the Maillard reaction. The apparent viscosity (ηa,10) and consistency index (K) values of the rehydrated solutions (60 g/ 180 mL water) increased with the increasing WPI ratio. These results may be useful for formulating protein-fortified milk powder with better instant properties.

Keywords: whey protein; milk powder; sarcopenia; fluidized bed; agglomeration