Food chemistry - beating eggs

OK, it sounds like some of you know the more technical end of WHY certain ingredients react the way they do in cooking. So here's my question.

What changes in an egg if you beat it for a long time? Specifically, I made an upside-down cake the other day. The recipe stated, "Beat 2 egg yolks for 5 minutes, until thick and lemon yellow." Thises then get sugar, flour, juices, etc added for cake batter.

Also, I have a recipe for a non-baked creamy pie filling that states, "Add 1 egg. Beat for 2 minutes. Add second egg. Beat for 2 minutes." This is a filling that is made of butter, sugar, cocoa and instant coffee flakes. No, the eggs never get cooked. Yes, I know about salmonella risk. But thats not the point; it was grandma's recipe and I'm gonna make it and eat the darn raw eggs.

What changes when you beat an egg for longer, rather than just a short turn with the mixer to combine white and yolk, or froth it a bit? And what happens that causes the yolks to look so thick and lemony after 5 minutes of beating?

Thanks for tellig me in plaing English. I'm not a pro chef, just a curious home baker.

Reply to
Jude
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"Jude" wrote in news:1140975171.440408.5840 @j33g2000cwa.googlegroups.com:

A slightly beaten egg is used to thicken or bind ingredients, and increases volume when scrambling eggs or cooking omelets. One-half minute of brisk beating with a fork or egg whisk is adequate for the purpose. Test the results by lifting the fork with adhering egg. If the egg flows from the fork easily and contains only a few air bubbles, it is slightly beaten.

A well beaten egg used for leavening is best performed using a rotary hand beater or electric mixer. Beat the egg until it is very frothy and changes to a white or light cream color. Egg yolk is thoroughly beaten when it becomes thick and has a uniform lemon color. A description of various egg beating stages as indicated in recipes are as follows.

Slightly beaten white is used to clarify, emulsify, and thicken solutions or in used in coating for meats and baked dishes. When beat for one-half minute, the white is slightly foamy but is still transparent and flows easily.

Stiff foam white is used in meringues that require a shiny, glossy and moist albumen. When the beaters or whisk is withdrawn, the albumen follows to form rounded peaks.

Stiff white is used in hard meringues, cakes, omelets, cooked frostings, candies, and marshmallows. Properly beat stiff white is no longer foamy and does not stick to the bowl when tipped, but remains glossy, smooth and moist.

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Reply to
Charles Quinn

If you beat longer there will come a time that the protein/ fat/sugar/ water emulsion will breakdown. There is a limit where the egg protein structure will entrap gas bubbles...As more air is incorporated it tends to dry up the moisture in between the bubbles which is one cause for bubbles to merge together increasing its diameter. The weakening of the pore cell structure is also brought about by the thinning of the protein membrane that entrap the bubbles. Another cause is emulsion destabilization etc...

When eggs is beaten the protein structure entrap gas bubbles; the more you beat it the finer the bubble size due to subdivision of the original bubble size but there is a limit, more beating will lead to drying which makes the foam stiff and becoming rigid and unable to expand. The moment you fold in the other ingredients it will interrupt the fragile bubble structure which is not flexible anymore due to lack of moisture. Therefore if you incorporate dry ingredients to an overbeaten foam it will result in poor volume cakes.

Whereas if the eggs are beaten optimally say until medium peak to stiff but not dry there is still enough moisture for it to remain flexible where you can add other ingredients .

If you beat it only slightly like scrambled eggs the fat in the egg yolk will tend to inhibit the formation of a water in oil emulsion (rather the reverse it will form a oil in water emulsion that is not prone to aeration )lessening the formation of air bubbles . But if you insist in beating for a long time( specially in the presence of sugar such as in sponge cake recipes) the emulsion will gradually stabilze as the fat component of the egg protein will be emulsifyied by the lecithin component with the available water ( in egg)forming a lipoprotein- glycoprotein complex. The sugar due to dissolution in water will increase the viscosity allowing the protein to form a film which will enable it to form bubbles.

As the fat tends to have weakening effect on the bubble structure, you will see that the nature of the whole egg protein foam is not as stiff as the egg white protein foam( in meringue)

Overbeating will lead to gradual foam breakdown which will led the small bubbles to merge making larger bubbles which led to the reduction of air pressure but the increase of unit bubble volume. As the pressure is not that strong anymore the foam structure is weaker and it cannot support the expansion of the batter to optimum volume. Physically the increase in bubble diameter results in increase of specific gravity *(or thinning of the batter in cakes).

Reply to
chembake

..Opps...Erratta

It should be it will tend to inhibit the formation of oil in water emulsion but rather the reverse, water in oil emulsiom which is not conducive to foaming.. But when beaten more specially in the presence of sugar, the emulsion will gradually stabilize as more moisture is bound by the sugar making it viscous liquid that promote the protein to foam. Further The resulting emulsion will be more stable as the balance of water is kept in check by the sugar and destabilization of the foam is reduced. There is still the presence of the lipoprotein- glycoprotein solution complex in the egg, sugar, water combinatikon that helps in the stabilization.

Reply to
chembake

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