Protein Extraction and Membrane Recovery in Enzyme‐Assisted Aqueous Extraction Processing of Soybeans

Abstract

Enzyme-assisted aqueous extraction processing (EAEP) is an environmentally friendly process in which oil and protein can be simultaneously recovered from soybeans by using water and enzymes. The significant amount of protein-rich effluent (skim) constitutes a challenge to protein recovery. Countercurrent two-stage EAEP at a 1:6 solids-to-liquid ratio, 50°C, pH 9.0, and 120 rpm for 1 h was used to extract oil and protein from dehulled, flaked and extruded soybeans. Different enzyme use strategies were used to produce different skim fractions: 0.5% protease (wt/wt extruded flakes) in both extraction stages; 0.5% protease only in the 2nd extraction stage; and no enzyme in either stage. Dead-end, stirred-cell membrane filtration was evaluated with each skim. About 96, 89, and 66% of the protein were extracted with the three enzyme treatments, respectively. Protein retentate yields of 91, 96, and 99% were obtained for the three enzyme treatments, respectively, by using double membrane filtration (30 kDa/500 Da) of the skims, achieving permeate fluxes up to 1.24 kg/m 2 h at 3.9-4.8 concentration factors (CF) and 0.56 kg/m 2 h at 1.9-2.9 CF for 30 kDa ultrafiltration and 500 Da nanofiltration, respectively. For cross-flow ultrafiltration with the 3-kDa membrane, pH and presence of insoluble protein aggregates significantly affected permeate flux. Maximum permeate flux occurred at high pH and in the presence of protein aggregates, achieving a mean value of 4.1 kg/m 2 h at 1.7 bar transmembrane pressure.

Pilot‐Plant Proof‐of‐Concept for Integrated, Countercurrent, Two‐Stage, Enzyme‐Assisted Aqueous Extraction of Soybeans

“…Mean and standard deviations are for seven replications at steady-state extraction were statistically different at P \ 0.05. Although greater extent of protein hydrolysis is generally associated with higher extraction yields [7], hydrophobicity and emulsification capacity of proteins may have increased with increased DH [17,18]. Our pilot-plant results were similar to those obtained in the laboratory when not recycling enzyme from the cream demulsification step into extraction [5].…”

“…Extensive research has been performed on enzyme-assisted aqueous extraction processing (EAEP) from soybeans [1][2][3][4][5][6][7][8][9][10] as an alternative to using hexane to extract edible oil from soybeans and a number of recent advances have been achieved [11]. In addition to eliminating the use of hazardous and polluting hexane, this water-and enzyme-based technology enables simultaneous fractionation of soybeans into oil-, protein-, and fiber-rich fractions suitable for converting into food, feed, and fuel.…”

Properties of Soy Protein Produced by Countercurrent, Two‐Stage, Enzyme‐Assisted Aqueous Extraction

“…Enzyme-assisted aqueous extraction processing (EAEP) of soybeans (using water and enzymes) is an environmentally intrinsically safe alternative to extraction processes involving hazardous and polluting hexane [4][5][6][7][8][9][10][11]. The combination of mechanical treatments (flaking and extruding), protease treatment, and countercurrent, two-stage, aqueous extraction can achieve similar oil extraction as hexane extraction but recoveries are about 80 % due to loss of oil in the protein-rich skim [4][5][6][7].…”

“…The combination of mechanical treatments (flaking and extruding), protease treatment, and countercurrent, two-stage, aqueous extraction can achieve similar oil extraction as hexane extraction but recoveries are about 80 % due to loss of oil in the protein-rich skim [4][5][6][7]. Different enzyme strategies for countercurrent, two-stage, EAEP were evaluated by de Moura et al [8], where protease was used in both extraction stages, in the second stage only, or without enzyme in either stage leading to 99, 94 and 84 % oil extraction and 96, 94 and 66 % protein extraction, respectively. Countercurrent, two-stage, protein extraction of air-desolventized, hexane-defatted, soybean flakes was used as a control and gave 85 % protein extraction [11].…”

Recovery of high value‐added protein from enzyme‐assisted aqueous extraction (EAE) of soybeans by dead‐end ultrafiltration

“…However, to our knowledge, only two studies have previously utilized UF to recover skim protein from EAE of soybeans (Campbell & Glatz, 2010;de Moura, Campbell, de Almeida, Glatz, & Johnson, 2011), and only Protex 6L was applied for enzymatic hydrolysis. However, information on the performance of UF to recover skim protein extracted with different proteases is still unknown.…”