Functional properties of whey protein concentrate texturized at acidic pH: Effect of extrusion temperature

Abstract

Reactive supercritical fluid extrusion (RSCFX) process at acidic condition (pH 3.0) was used to generate texturized whey protein concentrate (TWPC) and the impacts of process temperature on product's physicochemical properties were evaluated. TWPC extruded at 50 and 70 °C formed soft-textured aggregates with high solubility than that extruded at 90 °C that formed protein aggregates with low solubility. Total free sulfhydryl contents and solubility studies in selected buffers indicated that TWPC is primarily stabilized by noncovalent interactions. Proteins texturized at 90 °C showed an increased affinity for 1-anilinonaphthalene-8-sulfonate (ANS) and a decreased affinity for cis-parinaric acid (CPA), indicating changes in protein structure. Water dispersion of TWPC at room temperature showed thickening function with pseudoplastic behavior. Secondary gelation occurred in TWPC obtained at 50 and 70 °C by heating the cold-set gels to 95 °C. TWPC texturized at 90 °C produced cold-set gels with good thermal stability. Compared to control, TWPC formed stable oil-in-water emulsions. Factors such as degree of protein denaturation and the balance of surface hydrophobicity and solubility influenced the heat-and cold-gelation and emulsifying properties of the protein ingredients. TWPC generated by low and high temperature extrusions can thus be utilized for different products requiring targeted physicochemical functionalities.

Structural Changes in Rice Bran Protein upon Different Extrusion Temperatures: A Raman Spectroscopy Study

“…It was observed that the content of unordered structure increased up to 140 ∘ C and then decreased at 160 ∘ C, while the trend of -helix and -sheet content was opposite. Heat and shear alter the conformation of proteins through partial denaturation of the protein molecules, exposing groups that are normally concealed in the folded native protein, resulting in an increase of unordered structure [22]. Those observed Raman results were consistent with DSC study which suggest that extrusion may result in a denaturation of rice bran protein and partial exposure of hydrophobic cores initially buried in the interior.…”

“…Those observed Raman results were consistent with DSC study which suggest that extrusion may result in a denaturation of rice bran protein and partial exposure of hydrophobic cores initially buried in the interior. Proteins texturized at the higher temperature showed an increase in surface hydrophobicity and unfolding of protein structure [22], which may result in a progressively increase in unordered structure. Qi and Onwulata [5] indicated that extrusion results in a loss of secondary structure of around 15%, total loss of globular structure at 78 ∘ C, and conversion to a random coil at 100 ∘ C.…”

Enhanced stability of emulsions made with super‐critical carbon dioxide extruded whey protein concentrate

“…SC‐CO 2 also decreases the percentage of α‐helices and hydrogen bonds in the protein structure and increases β‐sheets, thus causing denaturation of globular proteins (Xu et al, ). All these factors also affect the emulsification characters of whey protein because denaturation of proteins is related to their surface hydrophobicity, protein flexibility, and the ratio of hydrophilic and hydrophobic residues (Fachin & Viotto, ; Nor Afizah & Rizvi, ).…”

Application of supercritical carbon dioxide extrusion in food processing technology

“…Texturized whey protein concentrate extruded at 50 and 70 °C formed soft-textured aggregates with higher solubility than products extruded at 90 °C which formed protein aggregates with lower solubility. Reactive supercritical fluid extrusion (RSCFX) process of whey protein concentrate at 50 and 70 °C caused only a minimal loss of protein solubility, whereas at 90 °C proteins were extensively denatured, causing a considerable increase in aggregates size and a reduction in solubility [46,47]. Cho and Rizvi (2008) investigated time-delayed expansion behaviour of SCFX extrudates via video analysis.…”