title: Improved emulsion stability by succinylation of patatin is caused by partial unfolding rather than charge effects.
abstract: 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 >30 mM 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 ≤200 mM. 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.
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
authors.forename: Roy J B M
authors.initials: RJ
authors.lastname: Delahaije
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Wierenga
authors.affiliation: AVEBE, Prins Hendrikplein 20, 9641 GK Veendam, The Netherlands.
authors.forename: Marco L F
authors.initials: ML
authors.lastname: Giuseppin
authors.affiliation: Laboratory of Food Chemistry, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands. Electronic address: harry.gruppen@wur.nl.
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000737:chemistry*; D004655:Emulsions; D010940:Plant Proteins / Q000737:chemistry*; D055550:Protein Stability; D058767:Protein Unfolding; D019802:Succinic Acid / Q000737:chemistry*
chemical_list: D004655:Emulsions; D010940:Plant Proteins; C043222:patatin protein, Solanum tuberosum; D019802:Succinic Acid; D002265:Carboxylic Ester Hydrolases
keywords: DLVO theory; Electrostatic interaction; Flocculation; Hydrophobicity; Interfacial properties; Modification; Molecular properties; Oil-in-water; Protein