Non-covalent binding of benzaldehyde to β-lactoglobulin: characterisation by spectrofluorimetry and electrospray ionisation mass-spectrometry

Abstract

β-Lactoglobulin (β-lg), which is found in the milk of several mammal species, is the most abundant protein in bovine whey (McKenzie, 1971). The interaction properties of β-lg with a large variety of small hydrophobic ligands have been extensively studied (Sawyer et al. 1998). β-Lg belongs to the super-family of hydrophobic molecule transporters called the lipocalins, which characteristically bind hydrophobic ligands inside a central calyx (Godovac-Zimmermann, 1988; Perez et al. 1989; Brownlow et al. 1997; Wu et al. 1997; Qin et al. 1998).At present, whey protein concentrates containing a high percentage of β-lg are commercially available in a very large quantity, but most of the processes used in milk technology involve heat-treatments that are known to affect the initial conformational state of β-lg. Such conformational changes have consequences for both the physicochemical and functional properties in food systems, including a decrease in the availability of lysine, due to Maillard reactions (Léonil et al. 1997) and a decrease in the affinity constant for binding to retinol (Laligant et al. 1991) and to flavour compounds (O'Neil & Kinsella, 1988). In the field of protein-volatile compound interactions, we have recently reported a significant enhancement of foaming properties of β-lg solutions (50 mM-NaCl, pH 6) in the presence of aroma compounds such as isoamyl acetate (Marin & Relkin, 1999), benzaldehyde (BZA; Marin & Relkin, 2000) and vanillin (Relkin & Vermersh, 2000). The observed increase in foaming properties of β-lg was postulated to be due to formation of surface active complexes between β-lg and aroma compounds.In the present work we have investigated the interaction between a β-lg concentrate (prepared by ultra-diafiltration on an industrial scale) and BZA; particularly, evidence was sought for the presence of covalently bound monomers, dimers and lactolated monomers.

Flavor Retention and Release from Beverages: A Kinetic and Thermodynamic Perspective

“…Understanding retention of flavors in a product requires measuring the variation of flavor present in at least one of the phases, liquid and/or gas, for which ample experimental methods are available for food matrices. For example, binding of volatiles to β-lactoglobulin has been investigated by O’Neill and Kinsella 22 by equilibrium dialysis, Andriot et al 23 by headspace analysis, Relkin et al 24 by spectrofluorometric measurement, and Rogacheva et al 25 used a diffusion cell. In the food field, interpretation of data is complex, leading to the use of (over)simplified systems, whereas predictive methods have gained relevance due to experimental limitations or high costs.…”

Structural Behaviour of Lipid Droplets in Protein-stabilized Nano-emulsions and Stability of α-Tocopherol

“…The fluorescence intensity values were corrected for absorbance effects, as previously described. 18 α-Tocopherol content in bulk and emulsified fat systems was determined just after preparation (t 0 ) and after storage at room temperature during 8 weeks before and after heating at 60°C for 180 min.…”

Hexanal and t-2-hexenal form covalent bonds with whey proteins and sodium caseinate in aqueous solution

“…The binding of aldehydes and especially 2-alkenals by soy proteins or whey proteins (WP) is only partly reversible (Gremli, 1974;Mills & Solms, 1984). Conversely, benzaldehyde does not bind covalently to b-lactoglobulin (Relkin, Molle, & Marin, 2001).…”