Dry fractionation of sunflower press cake as tool to improve its technofunctional properties

Depending on the oil production technology, at least 60% of the oilseeds input such as sunflower, pumpkin or canola remain as by-product, which is usually denoted as press cake (PC) and contains a significant amount of fiber and protein. Its further valorization in food requires knowledge on the technofunctional properties of the press cake and on possibilities for improving its value. Aim of the current study was to evaluate the effect of two separation techniques, namely targeted sieving and air classification, on composition, and physical as well as technofunctional properties of fractions of sunflower press cake previously milled to <1.0 mm or <2.0 mm. It is evident for both separation techniques that fines fractions obtained by using smaller sieves or lower air volume flow showed an increased protein content, with a protein enrichment factor of up to 1.47. Using PC < 2.0 mm as raw material, protein separation efficiency, a combined measure for protein content and yield, was higher after separation by air classification. Whereas protein solubility was not affected by the particle size distribution of the separated fractions, emulsion activity and emulsion stability were improved especially for the small particle fractions separated from PC < 2.0 mm.