A systematic study of the impact of the isoelectric precipitation process on the physical properties and protein composition of soy protein isolates. (January 2023)

• Record Type: Journal Article
• Authors: Verfaillie, Diete; Janssen, Frederik; Van Royen, Geert; Wouters, Arno G.B.
• Is Part Of: Food research international. Volume 163(2023)
• Publication Date: 2023-01
• Subjects: Soybean -- Protein isolation -- Protein composition -- Protein denaturation -- Solubility -- Colloidal state; BSA bovine serum albumin -- DLS dynamic light scattering -- DM dry matter -- DSC differential scanning calorimetry -- DTT 1, 4-dithiothreitol -- IEP isoelectric point -- MW molecular weight -- PAGE polyacrylamide gel electrophoresis -- SE-HPLC size-exclusion high-performance liquid chromatography -- SDS sodium dodecyl sulfate -- SPI soy protein isolate -- ΔH denaturation enthalpy -- Td denaturation temperature; Food -- Analysis -- Periodicals; Food industry and trade -- Periodicals; Food industry and trade -- Canada -- Periodicals; Food Technology -- Periodicals; Food -- Periodicals; Food-Processing Industry -- Periodicals; Aliments -- Industrie et commerce -- Périodiques; Aliments -- Industrie et commerce -- Canada -- Périodiques; Aliments -- Recherche -- Périodiques; Food industry and trade; Canada; Periodicals; Electronic journals; 664.005
• DOI: 10.1016/j.foodres.2022.112177
• Languages: English
• ISSNs: 0963-9969

Abstract

Graphical abstract: Highlights: The soy protein isolate (SPI) production process was systematically investigated. Hexane defatting of soy flour has no impact on its protein thermal properties. Alkaline extraction has no impact on soy protein physical properties or composition. SPI precipitated at pH 5.5 had highest protein solubility and lowest 7S/11S ratio. SPI solutions contain a considerable amount of aggregated protein structures. Abstract: The functional properties of soy protein isolates (SPIs), which are crucial for their successful use in food applications, depend on their protein physical properties and composition. Although the production process of SPIs is well-known and established industrial practice, fundamental knowledge on how the different isolation steps and varying isolation conditions influence these properties is lacking. Here, these characteristics were systematically investigated by assessing the impacts of the various steps of a conventional isoelectric precipitation based SPI production protocol. Protein denaturation and colloidal state were evaluated with differential scanning calorimetry and dynamic light scattering combined with (ultra)centrifugation, respectively. The protein composition (on protein subunit level) was assessed via size-exclusion chromatography. Hexane defatting was found not to cause protein denaturation. Alkaline extraction at pH values between 7.0 and 9.0 resulted in no differences in protein physical properties or composition. Subsequent acid precipitation at pH 5.5 resulted in SPIs with a lower 7S/11S ratio and higher protein solubility at neutral pH than when produced at pH 4.5 and 3.5. SPIs obtained at all evaluated precipitation pH values contained a considerable amount of aggregated protein structures. Spray-drying of SPI did not result in a higher degree of protein denaturation or in a loss of protein solubility compared to freeze-drying, but a smaller amount of soluble aggregates was observed in spray-dried SPIs. Hence, alterations in the isolation procedure can result in SPIs with moderately different physical properties and protein composition, which might lead to different functional properties and thus applicabilities in certain food systems.