Influence of Sodium Chloride and Glucose on the Aggregation Behavior of Heat‐Denatured Ovalbumin Investigated with a Multiangle Laser Light Scattering Technique

Abstract

The molecular characteristics of ovalbumin aggregates formed by heating with NaCl and glucose were investigated with a multi-angle laser light scattering system. The presence of NaCl and glucose affected the formation and molecular structure of the aggregates. Specifically, glucose increased the denaturation temperature of ovalbumin due to thermal stabilization of the native state of ovalbumin, regardless of the content of added NaCl. The surface hydrophobicity of the aggregates was increased by the addition of NaCl, which induced the denaturation of ovalbumin at a lower temperature. Aggregates with a larger weight-average molar mass (M(w)) and root mean square radius (R(g)) formed from heat-denatured ovalbumin with NaCl and glucose. The presence of NaCl during heat denaturation caused the formation of aggregates with a larger M(w) (1.9 x 10(5) and 3.5 x 10(6) g/mol for 0 and 10 mM NaCl, respectively) and R(g) (14.8 and 80.4 nm for 0 and 10 mM NaCl, respectively). Over a certain amount of NaCl, the addition of more glucose resulted in the formation of more aggregates with greater M(w) and R(g) values. In sum, the thermostability of ovalbumin was affected primarily by glucose, but the molecular characteristics of the soluble aggregates formed by heat denaturation varied primarily with NaCl content.

Influence of Sodium Chloride and Glucose on Acid‐Induced Gelation of Heat‐Denatured Ovalbumin

“…Bryant and McClements (1998) reported that the structure of protein aggregates could differ between those formed in the presence and absence of an electrolyte because of complete or partial screening of the electrostatic repulsion between the protein aggregates and the possibility of forming bonds between nonpolar groups due to attractive hydrophobic interaction. The weight‐averaged molar masses ( M w ) of ovalbumin aggregates prepared with 2, 5, and 10 mM NaCl were 2, 4, and 25 times greater than that without NaCl and 2, 3, and 5 times greater for the root mean square radius ( R g ), respectively (Choi and Moon 2007). In addition, the surface hydrophobicities (SHs) of ovalbumin aggregates prepared with 2, 5, and 10 mM NaCl were 1, 1.5, and 2 times greater than those without NaCl, respectively.…”

“…The M w , R g , and SH of ovalbumin aggregates that contained different NaCl concentrations were different from those of aggregates without NaCl. The M w of soluble aggregates that contained 0, 2, 5, and 10 mM NaCl were 1.86, 2.74, 6.83, and 34.90 × 10 6 g/mol, respectively, and the R g for soluble aggregates that contained 0, 2, 5, and 10 mM NaCl were 14.8, 25.4, 44.3, and 80.4, respectively (Choi and Moon 2007). In addition, the SHs of ovalbumin aggregates that contained 0, 2, 5, and 10 mM NaCl were 653, 684, 901, and 1465, respectively.…”

Kinetic Studies on the Effect of Salt on the Thermal Denaturation of Egg Constituents

“…The egg white sample had two endothermic peaks. From published literature [2,9], the first peak corresponded to ovotransferrin and the second peak corresponded to ovalbumin. Several factors, such as pH and the presence of salt or sucrose, are known to af fect denaturation temperatures [14].…”

“…Several studies have focused on changes in the physicochemical properties of egg constituents during heat treatment and these can be classified into two groups. One is the identification of the denaturation temperature of egg proteins, which are the major components of the egg, using differential scanning calorimetr y (DSC) [2][3][4][5][6][7][8][9]. The other focuses on the study of fluctuations of the gel-point temperature and rheological properties using dynamic viscoelastic oscillatory measurements [10][11][12][13].…”

“…Given the thermal sensitivity of eggs, great attention is given to the temperature of phase conversion. Moreover, since sucrose and salt are frequently added during processing of egg-containing food products [2,9,11,14], many studies have investigated the combined effects of pH, sugar, and salt addition on the gell-ing properties of eggs. As a result of the addition of salt, the aggregation of ovalbumin (the major egg white protein) was found to be significantly increased [9] and the denaturation temperatures of ovotransferrin (another egg white protein) and ovalbumin also increased [3,6].…”