Binding of 2-Nonanone and Milk Proteins in Aqueous Model Systems

Abstract

Interactions of the model flavor compound 2-nonanone with individual milk proteins, whey protein isolate (WPI), and sodium caseinate in aqueous solutions were investigated. A method to quantify the free 2-nonanone was developed using headspace solid-phase microextraction followed by gas chromatography with flame ionization detection. Binding constants (K) and numbers of binding sites (n) for 2-nonanone on the individual proteins were calculated. The 2-nonanone binding capacities decreased in the order bovine serum albumin > beta-lactoglobulin > alpha-lactalbumin > alpha s1-casein > beta-casein, and the binding to WPI was stronger than the binding to sodium caseinate. All proteins appeared to have one binding site for 2-nonanone per molecule of protein at the flavor concentrations investigated, except for bovine serum albumin, which possessed two classes of binding sites. The binding mechanism is believed to involve predominantly hydrophobic interactions.

Processing of phosphocasein dispersions by dynamic high pressure: Effects on the dispersion physico-chemical characteristics and the binding of α-tocopherol acetate to casein micelles

“…Thus, Sahu, Kasoju, and Bora (2008) assessed by fluorescence measurements, a saturation concentration of casein micelles of 17 μΜ for the complete binding of 5 μΜ curcumin in a buffered solution (pH 7.4). The evaluation of 2-nonanone or vanillin affinity to sodium caseinate or individual caseins (Kühn, Zhu, Considine, & Singh, 2007;Li, Grün, & Fernando, 2000) reported a number of binding sites of 0.8-1 for both aroma compounds to sodium caseinate or α s1 -casein, and 0.3 for 2-nonanone to β-casein.…”

“…Surface hydrophobicity of casein micelles in skim milk was thus evaluated by Gatti, Risso, and Pires (1995) and Gatti, Risso, and Zerpa (1998) using hydrophobic markers such as 1,8-anilinonaphthalenesulfonate (ANS), 2(p-toluidinyl) naphthalene-6-sulfonate (TNS) or Nile Red, to measure its interaction with casein micelles by fluorescence spectroscopy. Kühn, Zhu, Considine, and Singh (2007) studied the binding of a hydrophobic aroma compound, 2-nonanone (0.1-0.8 mM) to individual α s1 and β caseins, sodium caseinate or whey proteins (0.5-2%, w/v) at pH close to 6.8.…”

Characterization of resveratrol–milk protein interaction

“…BSA has been widely used in drug delivery studies because of its abundance, low cost, ease of purification, and unusual ligand-binding properties (Elzoghby et al, 2012). Previous studies showed that BSA has the highest binding capacity and considerable surface activity among other individual milk proteins (Singh and Ye, 2009;Kühn and Zhu, 2007;Livney, 2010). Moreover, the interaction between resveratrol and human serum albumin assessed by CD spectroscopy, showed no major alterations at low resveratrol concentrations.…”

Effect of Ultra-High Pressure Homogenization on the Interaction Between Bovine Casein Micelles and Ritonavir

“…In this regard, a number of works have demonstrated the natural tendency of individual caseins or casein micelles to bind bioactive compounds such as vitamin D (13), the flavor compound 2-nonanone (14), anticancer drugs such as mitoxantrone (15), curcumin (16), docosahexaenoic acid (DHA) (17), tea catechins (18) and β-carotene (19). …”