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

Abstract

Enzyme-assisted aqueous extraction processing (EAEP) is an environmentally friendly technology where oil and protein can be simultaneously extracted from soybeans by using water and protease. Countercurrent, twostage, EAEP was performed at a 1:6 solids-to-liquid ratio, 50°C, pH 9.0, and 120 rpm for 1 h to extract oil and protein from soybeans. The skim fractions were produced by three methods: (1) by treating with 0.5 % protease (wt/g extruded flakes) in both extraction stages; (2) by treating with 0.5 % protease in the 2nd extraction stage only; and (3) by using the same two-stage extraction procedure without enzymes in either extraction stages. Countercurrent, two-stage, protein extraction of air-desolventized, hexane-defatted, soybean flakes was used as a control. Solubility profiles of the skim proteins were the typical U-shaped curves with the lowest solubility at the isoelectric point of soy protein (pH 4.5). The use of the enzyme slightly improved solubility of the recovered protein with hydrolyzed proteins having higher solubilities at acid pH. Emulsification and foaming properties were generally reduced by the use of enzyme during EAEP extractions. The skims produced with protease-extracted (hydrolyzed) proteins gave gels with lower hardness than did unhydrolyzed proteins when heated at 80°C. The essential amino acid compositions and protein digestibilities were not adversely affected by either extrusion or extraction treatments. Treatment 1: protein extract (skim) from countercurrent, 2-stage EAEP of extruded full-fat soybean flakes using protease in both extraction stages; Treatment 2: protein extract (skim) from countercurrent, 2-stage EAEP of extruded full-fat soybean flakes using protease in the second extraction stage only; Treatment 3: protein extract (skim) from countercurrent, 2-stage, EAEP of extruded full-fat soybean flakes without using protease in either extraction stage; Treatment 4: protein extract from countercurrent, 2-stage, EAEP of air-desolventized, hexane-defatted, soybean flakes without using protease in either extraction stage A,Means (two independent extraction batches analyzed in triplicate) within the same group of analysis (emulsification capacity, emulsification activity, emulsification stability) followed by different superscripts are statistically different at P \ 0.05 J Am Oil Chem Soc (2014) 91:1077-1085 1081 Treatment 1: protein extract (skim) from countercurrent, 2-stage EAEP of extruded full-fat soybean flakes using protease in both extraction stages; Treatment 2: protein extract (skim) from countercurrent, 2-stage EAEP of extruded full-fat soybean flakes using protease in the second extraction stage only; Treatment 3: protein extract (skim) from countercurrent, 2-stage, EAEP of extruded full-fat soybean flakes without using protease in either extraction stage; Treatment 4: protein extract from countercurrent, 2-stage, EAEP of air-desolventized, hexane-defatted, soybean flakes without using protease in either extraction stage J Am Oil Chem Soc (2014) 91:

Aqueous Extraction of Oil and Protein from Soybeans with Subcritical Water

“…Heating favors protein-lipid interactions in which denatured protein is likely to sequester oil by exposing hydrophobic amino acids [22]. Since soybean flakes and extruded soybean flakes contain proteins with different solubilities [27] due to protein denaturation during extrusion, one would expect lower protein extractability when using extruded soybean flakes compared with soybean flakes. Protein extraction yields from soybean flakes and from extruded soybean flakes ranged from 31 to 72 and 27 to 73%, respectively.…”

Yield of Soybean Protein Isolate from Defatted Soybean Flakes Treated in an Industrial Plant and in Laboratory: Experiments and Modeling

“…; Newkirk ; de Almeida et al . ), e.g., to enhance the texture, form emulsions and increase or replace protein (Lai et al . ; Li et al .…”

“…; de Almeida et al . ), but the procedure typically adopted in large‐size plants is essentially based on protein extraction/solubilization at alkaline pH, and precipitation by acidification to the isoelectric pH of soybean proteins (Berk ; Wang et al . ; Alibhai et al .…”

“…Many Brazilian industries also treat the defatted soybean flakes (DSFs) or meal to produce soybean protein isolate (SPI), which is the more concentrated type of soybean protein product commercially available (>90% of protein in dry basis) (Wang et al 1998(Wang et al , 2004Alibhai et al 2006;Lai et al 2013). It is largely used as an additive in manufactured food products (Berk 1992; Barbosa et al 2006;Newkirk 2010;de Almeida et al 2014), e.g., to enhance the texture, form emulsions and increase or replace protein (Lai et al 2013;Li et al 2014).…”

Functionality-driven fractionation the need for mild food processing

“…The application of a centrifugation step yields three phases; i) a cream layer, which is rich in oil, ii) a liquid phase, which is rich in protein, and iii) a pellet, rich in insoluble fibers. The aqueous phase can be used as starting material for protein fractionation by acid precipitation (de Almeida et al 2014;Russin et al 2011;Campbell et al 2011). Soy beans or soy flour are often toasted to decrease the enzyme activity and anti-nutritional factors (Kakade et al 1974), but this toasting step also lowers the solubility (Wu and Inglett 1974;Onimawo and Akpojovwo 2006).…”