Influence of Egg Storage Time - METTLER TOLEDO

Influence of Egg Storage Time

Sample

Commercially available eggs, class A

Packaging date: June 6

Purchase date: June 18

 

Conditions

Measuring cell: DSC20

Pan: Aluminum standard 40 µl, hermetically sealed

Reference: Approximately the same amount of water

Sample preparation: Storage of the eggs in a physiological saline solution at 30 °C. At the end of the storage time, the egg white was separated and stirred for two minutes.

DSC measurement: Heating from 30 °C to 110 °C at 5 K/min

Interpretation

In addition to the spontaneous transitions due to the influence of heat or pH, slower conformational changes also occur in food and can be measured by DSC if the reaction behavior of the stored products changes. For instance, the storage time (including also the post-mortem phase of meat) can be deduced if required. The above-mentioned reactions include the protein rearrangement of ovalbumin in egg white to S-ovalbumin (or retrogradation in the case of carbohydrates). Fresh egg white shows an ovalbumin denaturation peak at 86 °C (first day). After a storage time of just two days, two maxima appear at 88 °C and 91 °C, a sign that the rearrangement to S-ovalbumin has started. After five days the main maximum has shifted to 91 °C. After twelve days the entire protein fraction has changed to the S-conformation with a peak maximum at 91 °C. The shift in the peak temperature correlates directly with the storage time.

 

Evaluation 

Conclusion

Even though the shift of the peak maximum between the fresh sample and the sample stored for twelve days is only 5 K, the measurement is so reproducible, that within the first ten days of storage the storage time can be readily estimated to the nearest two days. After the complete rearrangement of the ovalbumin fraction to S-ovalbumin, it is no longer possible to follow the storage time.

 

Influence of Egg Storage Time | Thermal Analysis Application No.HB1008 | Application published in METTLER TOLEDO TA Application Handbook Food.