The Morphology of Instant Whole Milk Powder from Different Industrial Plants

Abstract

The ability of instant whole milk powder (IWMP) to rapidly dissolve in water depends on its particle size distribution and agglomeration characteristics. This work develops an experimental technique to measure the morphological parameters of IWMP for inferring the state of agglomeration and then uses this data to compare powder produced from different industrial plants with differing dissolution properties. Light microscopy was used in combination with image processing in order to extract shape parameters such as the circularity, convexity, solidity and elongation for individual milk powder particles. It was found that the generated shape distributions were dominated by the large number of fine particles (number basis), and shape parameters were more meaningful for particles with a large diameter, which dominate on a mass basis. This meant that to find differences in the same type of powder, a large sample size, data pre-processing and filtering were all necessary to get a sufficient number of large particles for adequate shape characterisation. It was expected that the convexity and solidity would be good measures of agglomeration by quantifying the “openness” of the agglomerate and that lower convexity and solidity would correlate with dissolution properties. However, it was found that the powder from the plant with superior dissolution properties generally had higher convexity and solidity. In summary the combination of cost-effective light microscopy with simple image processing techniques allowed one to rapidly generate meaningful statistical distributions correlating shape factors with key functional properties for milk powder.