Production and characterization of fat based powder-liquids and powder-liquid mixtures

• Fat based “powder-liquids” were produced and characterized.
• Ring shear tests were performed on the single powders and mixtures.
• The flow behavior varied with particle size, due to Van der Waals forces.
• The flow behavior varied with powder-liquid concentration.
• The flow behavior varied with temperature, due to solid fat content.

So called powder-liquids show high potential to be used in functional food and pharmaceutical systems. Powder-liquids are liquids in a powdery state, produced in a spray chilling process, and are beneficial when adding small amounts of liquids into a bulk powder, avoiding clogging and/or lump formation. Our aim was to produce and characterize fat based powder-liquids and study them in terms of particle size distribution, particle morphology and flow behavior. Detailed knowledge of the physical properties is of major relevance to industry, considering powder-storage, -handling and -processing. Ring shear testers are well known for assessing flow properties of powders. Within this work we extended and proved its applicability to powder-liquid systems, which to our knowledge is a fully new approach. In doing so, we could demonstrate that both particle size and temperature had a significant influence on the powder-liquid flow behavior; and that the ring shear tester worked surprisingly well when applied on such uncommon powdery systems. Differences in flow behavior for various size fractions stemmed from larger Van der Waals forces between smaller particles, whereas the temperature-dependence arose from different solid fat contents of the powder-liquids. The obtained results led to a better understanding of powder-liquids and their mixtures, applicable in post-processed products of high homogeneity, stability and reduced liquid amounts without the additional use of stabilizers.

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