Scale-up of Enzyme-Assisted Aqueous Extraction Processing of Soybeans

The effects of scaling-up enzyme-assisted aqueous extraction process (EAEP) using 2 kg of flaked and extruded soybeans as well as the effects of different extrusion and extraction conditions were evaluated. Standard single-stage EAEP at 1:10 solids-to-liquid ratio (SLR) was used to evaluate the effects of different extruder screw speeds and whether or not collets were extruded directly into water. Increasing extruder screw speed from 40 to 90 rpm improved oil extraction yield from 85 to 95%. Oil, protein, and solids extraction yields of 97, 86, and 78% were obtained when extruding directly into water and 95, 84, and 77% when not extruding into water. When not extruding into water, standard single-stage EAEP (1:10 SLR) yielded 95, 84, and 77% of total oil, protein, and solids extraction, respectively, and two-stage countercurrent EAEP (1:6 SLR) yielded 99, 94, and 83% total oil, protein, and solids extraction, respectively. These yields were similar to those previously obtained in the laboratory (0.08 kg soybeans), but higher oil contents were observed in the skim fractions produced at pilot-plant scale for both processes. Modifying processing parameters improved the oil distribution among the fractions, increasing oil yield in the cream fraction (from 76 to 86%) and reducing oil yield in the skim fraction (from 23 to 12%). Steady-state oil extraction was achieved after two 2-stage extractions. Two-stage countercurrent EAEP is particularly attractive due to reduced water usage compared to conventional single-stage extraction.