Improved emulsion stability by succinylation of patatin is caused by partial unfolding rather than charge effects

• Published in: Journal of colloid and interface science Vol. 430; no. 430; pp. 69 - 77
• Main Authors: Delahaije, Roy J.B.M., Wierenga, Peter A., Giuseppin, Marco L.F., Gruppen, Harry
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15-09-2014; Elsevier
• Subjects: Adsorption; beta-lactoglobulin; Carboxylic Ester Hydrolases - chemistry; Charge; Chemistry; Colloidal state and disperse state; dependence; DLVO theory; drop size; Electrostatic interaction; Emulsions; Emulsions. Microemulsions. Foams; Exact sciences and technology; Flocculating; Flocculation; General and physical chemistry; Hydrophobicity; in-water emulsions; interface; Interfacial properties; Modification; Molecular properties; Molecular structure; Oil-in-water; Plant Proteins - chemistry; Protein; Protein Stability; Protein Unfolding; protein-exposed hydrophobicity; Proteins; Stability; stabilization; Succinic Acid - chemistry; Surface physical chemistry; Modification; Flocculation; Molecular properties; Electrostatic interaction; Oil-in-water; Interfacial properties; Hydrophobicity; DLVO theory; Protein; Water; Stability; Emulsion; Oil; Interface
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2014.05.019

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•Succinylation of patatin results in increased charge and (partial) unfolding.•Partial unfolding increases the initial adsorption rate to the oil–water interface.•Higher adsorption rate increases the amount of protein in the continuous phase.•Excess protein in the continuous phase stabilizes against salt-induced flocculation.
This study investigates the influence of succinylation on the molecular properties (i.e. charge, structure and hydrophobicity) and the flocculation behavior of patatin-stabilized oil-in-water emulsions. Patatin was succinylated to five degrees (0% (R0) to 57% (R2.5)). Succinylation not only resulted in a change of the protein charge but also in (partial) unfolding of the secondary structure, and consequently in an increased initial adsorption rate of the protein to the oil–water interface. The stability against salt-induced flocculation showed two distinct regimes, instead of a gradual shift in stability as expected by the DLVO theory. While flocculation was observed at ionic strengths >30mM for the emulsions stabilized by the variants with the lowest degrees of modification (R0–R1), the other variants (R1.5–R2.5) were stable against flocculation ⩽200mM. This was related to the increased initial adsorption rate, and the consequent transition from a protein-poor to a protein-rich regime. This was confirmed by the addition of excess protein to the emulsions stabilized by R0–R1 which resulted in stability against salt-induced flocculation. Therefore, succinylation of patatin indirectly results in stability against salt-induced flocculation, by increasing the initial adsorption rate of the protein to the oil–water interface, leading to a shift to the protein-rich regime.