This is a contribution to the #FoodChem Carnival.
One of the stranger things in Henley’s was
the obsession with eggs and egg-whites. An entire section was devoted to egg-white based beverages, and egg dating and preservation were hot topis. Under proper conditions it is apparently possible to preserve eggs at room temperature for up to one year (water/sodium silicate), though the authors do remark that the taste suffers slightly.
While the yolk of an egg holds most of the delicious fats, the protein rich egg white is of greater use to a chemist. Fine particles can be very difficult to remove from solvated compounds via simple filtration, as they simply slide through most filters. This is especially problematic during wine making, when polymerized tannins and yeast proteins will leave a faint haze in the finished product.
The solution is to aggregate these particles into larger molecules that can be easily filtered. Egg whites are ideal for this purpose, as they can be poured in at room temperature and then denatured by raising the temperature above 70°C. As the ovalbumin and other egg proteins clump together they will abstract insoluble materials from the solution, leaving behind the soluble compounds as a clear liquid. In Henley’s the technique is listed under clarification, and is written as a general solution to the filtration problem. I’ve never heard of the technique in an organic chemistry lab, but given the low price of eggs (and the high price of sub-micron filters) I may have to experiment.
An addendum: How to determine egg age.
The age of eggs may be approximately judged by taking advantage of the fact that as they grow old their density decreases through evaporation of moisture. [snip] The New York State Experiment Station studied the changes in the specific gravity of the eggs on keeping and found that on average fresh eggs had a specific gravity of 1.090; after they were ten days old, of 1.072; after twenty days, of 1.053; and after 30 days, of 1.035. The test was not continued further.
[snip]
Make a solution of cooking salt in rain or distilled water, of about one part of salt to two parts of water, and in this place the eggs to be tested. A perfectly fresh egg (of from 1 to 36 hours old) will sink completely, lying horizontally on the bottom of the vessel; when from two to three days old, the egg also sinks, but not to the bottom, remaining just below the surface of the water, with a slight tendency of the large end to rise. In eggs four or five days old this tendency of the large end to rise becomes more marked, and it increases from day to day, until at the end of the fifth day the long axis of the egg (an imaginary line drawn through the center lengthwise) will stand at an angle of 20° from the perpendicular. This angle increases daily, until at the end of the eighth day it is at about 45°; on the fourteenth day it is 60°; on the twenty-first it is 75°, while at the end of four weeks the egg stands perfectly upright in the liquid, the point or small end downward.
Pingback: The #Foodchem Carnival recap | Grand CENtral