Egg white
Measuring cell: DSC20
Pan: Aluminum standard 40 ul, hermetically sealed
Reference: Approximately the same amount of water
Sample preparation: After weighing the egg white, the sealed pan is immersed in a thermostatted water bath (80 °C) for the specified exposure times.
DSC measurement: Heating from 30 °C to 110 °C at 10 K/min
Denaturation occurs during the pretreatment so that the remaining reaction enthalpy decreases with increasing exposure. The conalbumin fraction is no longer detected in the sample treated for 30 seconds, which shows that the sample has been heated to at least 80°C. The intact ovalbumin peak with a double maximum at 83°C and 88 °C shows that the temperature did not exceed 80 °C. With increasing treatment time, the peak shifts to an absolute maximum at 90°C. This thermicly induced rearrangement is the transition from ovalbumin to the thermicly more stable form S-ovalbumin (see also the next application example). The fact that the reaction enthalpy remains constant shows that neither the ovalbumin nor the S-ovalbumin fraction are significantly damaged by the heat treatment. The rearrangement is irreversible and takes place via intermediate products. The increased thermic resistance is a consequence of a change in the covalent structure. The pH value increases from 8.1 to 9.0. The transition to the more heat resistant structure amounts only to about 10% of the usual enthalpy of denaturation.
The measurements show that DSC can both verify the extent of thermal treatment (for proof of the treatment) and determine the influence of the process parameters temperature/time on the protein quality for process optimization purposes.
Influence of Thermal Treatment of Egg White | Thermal Analysis Application No. HB 1011 | Application published in METTLER TOLEDO TA Application Handbook Food