Fractionation of Edible Fats: Model Fat-Oil Separation in Decanter Centrifuge

In this work, the use of a lab-scale decanter centrifuge for the separation of fat crystal agglomerates from oil is studied. For this purpose, a model system of fully hydrogenated rapeseed oil and canola oil is used. The goal is the continuous mechanical de-oiling of the oil-fat slurry. The impact of the particle size and poly-dispersity of the slurry in combination with the process parameters, pool depth, flowrate, differential speed, and centripetal acceleration, is evaluated. These parameters lead to forces and particles’ velocities that actuate the oil/fat separation. The characteristic ones are theoretically calculated and the impact of each on the solids content in the liquid fraction and in the cake is assessed. The success of each separation process is measured through gas chromatography and light microscopy data. It is found that high hydrostatic pressure on the bowl wall—it already starts from the pool—leads to a compacted cake. At the next step, which happens on the dry beach, low cake axial transport velocity provides enough time for the olein to be removed from the cake pores. These two phenomena, especially in combination, lead to high cake dryness. For a fully continuous dry fractionation process, future research should be focused on the fat crystallization step.

Practical applications: A decanter centrifuge is used to study an alternative to the conventional dry fractionation, which employs filtration to separate fat crystal agglomerates from liquid oil. The goal is to offer higher separation efficiencies, more energy and time efficiency, the potential for a fully continuous dry fractionation, less space demands, and process selectivity. Especially the latter, could be utilized as a tripalmitin-selective alternative method to the current multistep dry or solvent fractionation.