Evaluation of the drying kinetics of micellar casein concentrate and reduced-mineral micellar casein concentrate at different solids concentrations.

Document Type

Abstract

Publication Date

2018

Publisher

American Dairy Science Association

Journal

Journal of Dairy Science

Volume

101

Issue

Suppl. 2

Pages

8

Language

en

Keywords

single droplet drying, micellar casein concentrate, reduced-mineral micellar casein concentrate

Abstract

Micellar casein concentrate (MCC) was prepared by microfiltration and diafiltration of skim milk to produce a retentate with approximately 22% total solids (95% casein as a percentage of true protein). Modified (reduced mineral) micellar casein concentrate (MMCC) was prepared by diluting the MCC retentate to 7% solids and injecting CO2 to pH 5.9 and ultrafiltered to produce a retentate with approx. 22% total solids. Three sets of trials were performed on separate skim milk lots for both MCC and MMCC. The drying kinetics of the MCC and MMCC from each trial were then studied using single droplet drying (SDD). The SDD approach involves a single droplet suspended on the tip of a glass filament, where changes in droplet diameter, mass, and temperature can be measured during drying. The aim of this study was to develop and compare a predictive model generated using SDD for MCC and MMCC which can be used as a tool to optimize the drying conditions and reduce costly plant trials when developing new ingredients with unique functional properties. In this study, 2 ± 0.05 µL droplets of MCC and MMCC were dried using SDD at 2 different levels of total solids: 10% and 20% at 90°C with hot air at a velocity of 0.8 m/s. Droplet diameter and mass change data were collected and processed using Adobe After Effects 7.0 to enable the extraction of images. Although the pattern of change in average diameter data obtained from SDD was same for both MCC and MMCC, there was a significant difference observed during the average diameter change between MCC and MMCC (P < 0.05) at both the solids level MCC showed a rapid change in average diameter compared with MMCC. The curves of average mass change obtained from SDD were plotted against time. It was observed that as the total solids level increases the drying time increases, which is mainly due to the formation of crust on the particle and subsequent slower moisture migration to the surface of the particle with higher total solids level in both MCC and MMCC.

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