High pressure thermal denaturation kinetics of whey proteins

Abstract

Pressure processing of foodstuff has been applied to produce or modify proteinaceous gel structures. In real pressure processing the treatment is non-isothermal, due to the adiabatic nature of the process and the heat loss from the product to the vessel. In order to estimate the effect of pressurization on milk constituents pressure and temperature dependent kinetics were determined separately from each other. In a detailed kinetic study whey protein isolate was treated under isobaric (200 to 800 MPa) and isothermal conditions ( -2 to 70 8C), and the resulting degree of denaturation of b-lactoglobulin A and B and a-lactalbumin was analysed. Kinetic parameters of denaturation were estimated using a one step non-linear regression method which allowed a global fit of the whole data set. The isobaric isothermal denaturation of b-lactoglobulin and a-lactalbumin was found to follow third and second order kinetics, respectively. Isothermal pressure denaturation of both b-lactoglobulin fractions do not differ significantly and were characterized by an activation volume decreasing with increasing temperature from -10 to about -30 ml mol -1 , which demonstrates that the denaturation rate is accelerated with increasing temperature. The activation energy of about 70 to 100 kJ mol -1 obtained for b-lactoglobulin A and B is not dependent to a great extent on the pressure which indicates that above 200 MPa denaturation rate is limited by the aggregation rate while pressure forces unfolding of the molecule.

Effect of high-pressure treatment on denaturation of bovine β-lactoglobulin and α-lactalbumin

“…The order of reaction published for the pressure denaturation of b-lactoglobulin ranges between 2 and 3. Anema et al [19] and Hinrichs and Rademacher [20] assumed a reaction order of n = 2 for b-lactoglobulin variants A and B treated in milk and in whey protein solutions, whereas a reaction order of n = 2.5 [21] and n = 3 [22] has been also reported for the denaturation of both protein variants by high-pressure treatment.…”

“…Denaturation of individual whey proteins in these works has been determined using electrophoresis [19,20] and reversed-phase high performance liquid chromatography (RP-HPLC) [21,22] after subjected pressure-treated milk or whey protein isolate samples to acid precipitation at pH 4.6, to remove precipitated casein and aggregated whey proteins. The order of reaction determined for the pressure-induced denaturation of b-lactoglobulin was found to range between 2 and 3 [19][20][21][22] and of a-lactalbumin between 2 and 2.5 [20][21][22].…”

Kinetics of combined thermal and pressure-induced whey protein denaturation in bovine skim milk

“…The kinetic parameters (order of reaction, rate constant at reference pressure and temperature and activation volume) were estimated by means of non-linear regression with an overall fit, using the ''one-step method''. This method allows a more accurate estimation of the kinetic parameters compared to the differential and integration methods (Cohen & Saguy, 1985;Ludikhuyze, 1998;Taoukis et al, 1998;Claeys, Ludikhuyze, Loey, & Hendrickx, 2001;Hinrichs & Rademacher, 2004). All regressions were carried out using the software package SigmaStat 1.0 (Jandel Scientific, Erkrath, Germany).…”

“…It is probable that the molecular structure of a-La is more stable than that of b-Lg, and only if during unfolding free SH-groups are available from other molecules, oligomerisation takes place (Lo´pez-Fandin˜o et al, 1996;Hinrichs, Rademacher, & Kessler, 1996;Gaucheron et al, 1997). In addition, the rate of whey protein denaturation increases with rising temperature and falls with decreasing temperature when starting at ambient temperature (Gaucheron et al, 1997;Lo´pez-Fandin˜o & Olano, 1998;Garcia-Risco, Olano, Ramos, & Lo´pez-Fandin˜o, 2000;Hinrichs & Rademacher, 2004).…”

Probing thermal transitions and structural properties of gluten proteins using ultrasound

“…Most denaturation changes consist of changes in secondary bonds: ion-dipole, hydrogen and Van der Waals, and in the rotational positions about single bonds which are controlled by the secondary bond structure [28]. Although denaturation can be achieved by a number of methods such as raising the temperature [29,30], changing pH [31], using various denaturant chemicals [31,32], and high pressure homogenization [33], since the results reported in this paper deal with denaturation achieved solely with increasing temperature, the other methods will not be discussed further.…”