Separating Oil from Aqueous Extraction Fractions of Soybean

Abstract

Abstract Previous research has shown that enzyme‐assisted aqueous extraction processing (EAEP) extracts 88–90% of the total soybean oil from extruded full‐fat soy flakes into the aqueous media, which is distributed as cream (oil‐in‐water emulsion), skim, and free oil. In the present work, a simple separatory funnel procedure was effective in separating aqueous skim, cream and free oil fractions allowing mass balances and extraction and recovery efficiencies to be determined. The procedure was used to separate and compare liquid fractions extracted from full‐fat soy flour and extruded full‐fat soy flakes. EAEP extracted more oil from the extruded full‐fat soy flakes, and yielded more free oil from the resulting cream compared to unextruded full‐fat soy flour. Dry matter partitioning between fractions was similar for the two procedures. Mean oil droplet sizes in the cream and skim fractions were larger for EAEP of extruded flakes compared to non‐enzymatic AEP of unextruded flour (45 vs. 20 μm for cream; 13 vs. 5 μm for skim) making the emulsions from EAEP of extruded flakes less stable. All major soy protein subunits were present in the cream fractions, as well as other fractions, from both processes. The cream could be broken using phospholipase treatments and 70–80% of total oil in the extruded full‐fat flakes was recovered using EAEP and a phospholipase de‐emulsification procedure.