Kinetic Study on the Changes in the Susceptibility of Egg White Proteins to Enzymatic Hydrolysis Induced by Heat and High Hydrostatic Pressure Pretreatment

Abstract

A kinetic study was conducted on the effect of heat pretreatment in the temperature range of 50-85 degrees C at atmospheric pressure and of high hydrostatic pressure pretreatment (100-700 MPa) at four temperatures (10, 25, 40, and 60 degrees C) on the susceptibility of egg white solutions (10% v/v, pH 7.6) to subsequent enzymatic hydrolysis by a mixture of trypsin and alpha-chymotrypsin at 37 degrees C and pH 8.0. Both heat pretreatment at atmospheric pressure and high-pressure pretreatment resulted in an increase in degree of hydrolysis (DH) after 10 min of enzymatic reaction (DH10) of egg white solutions, as measured using the pH-stat method, which could be described by a fractional conversion model (based on an apparent first-order reaction kinetic model). The temperature dependence of the corresponding rate constants could be described by the Arrhenius equation. At elevated pressure, a negative apparent activation energy was obtained, implying an antagonistic effect of pressure and temperature. The pressure dependence of the rate constants could be described by the Eyring equation, and negative activation volumes were observed, which demonstrates the positive effect of pressure on the susceptibility of egg white solutions to subsequent enzymatic hydrolysis.

Kinetic study on the combined effect of high pressure and temperature on the physico-chemical properties of egg white proteins

“…The smaller size of the aggregates formed at elevated pressure might explain why the resulting suspensions were less turbid. Pressuretreated egg white proteins are also more flexible, as evidence by the higher susceptibility to enzymatic hydrolysis in an earlier study (Van der Plancken, Delattre, Indrawati, Van Loey, & Hendrickx, 2004). These more moderate changes in protein structure due to pressurization as compared to heat-treatment can be of interest for their surface properties, like foaming and emulsifying capacity.…”

Improvement of techno-functional properties of edible insect protein from migratory locust by enzymatic hydrolysis

“…This leads to the assumption that all applied heat pre-treatments favoured thermal aggregation reactions and, hence, impeded enzymatic cleavage of the locust proteins due to masking of previously exposed cleavage sites. In contrast, thermal pre-treatment of other proteins such as egg white (50-77 °C, 20 min), pea (100 °C, 30 min) and whey protein (80 °C, 15 min) were reported to enhance subsequent enzymatic hydrolysis by protein reorientation and exposure of previously hidden sites [53][54][55]. In contrast, heat pretreatment of lotus seed protein (> 60 °C, 75 min) led to an impaired enzymatic degradation comparable to the present findings, which was ascribed to thermal protein aggregation [56].…”

Foaming properties of egg white proteins affected by heat or high pressure treatment

“…Similar to heat-treatment, pressure treatment of egg white proteins above 450 MPa results in a loss of secondary structure (Hayakawa, Linko, & Linko, 1996). These pressure-induced structural changes in egg white proteins can also be demonstrated by the exposure of previously buried hydrophobic and SH groups and increased flexibility (measured as susceptibility to enzymatic hydrolysis) (Iametti et al, 1998(Iametti et al, , 1999Van der Plancken et al, 2004, 2005bVan der Plancken, Van Loey, & Hendrickx, 2005a, Van der Plancken, Van Loey, & Hendrickx, in press). However, the increase in surface hydrophobicity is less pronounced at elevated pressure, compared to elevated temperature at ambient pressure.…”

“…It is known that heat-treatment can induce protein denaturation, which can, depending on the severity of the process, result in changes in the functional properties of the treated proteins. The correlation between the structural properties of egg white proteins and their functional properties has been the subject of many studies, with an emphasis on the contribution of the major egg white protein, ovalbumin (Donovan, Mapes, Davis, & Garibaldi, 1975;Kato, Fujimoto, Matsudomi, & Kobayashi, 1986;Mine, Noutomi, & Haga, 1990; Van der Plancken, Delattre, Indrawati, Van Loey, & Hendrickx, 2004;Van der Plancken, Van Remoortere, Indrawati, Van Loey, & Hendrickx, 2003;Van der Plancken, Van Loey, & Hendrickx, 2005b, 2006. In these studies much attention was paid to the changes in structural properties of ovalbumin or the other egg white proteins induced by heating, leading to changes in the functional properties.…”