7 Facts You Didn't Know About Eggs

By America's Test Kitchen | Yahoo Food – Fri, 27 Mar, 2015

As an ingredient, eggs are indispensable in the kitchen. They can bind, thicken, emulsify, clarify, and even leaven. They are also incredibly versatile on their own and can be prepared in a number of different ways: fried, scrambled, poached, hard-cooked, baked, shirred, and made into omelettes and frittatas. Read on for some deep egg knowledge we’ve gleaned in the Test Kitchen.

1. Some recipes for scrambled eggs call for water or milk. Does this do anything for the eggs?

When eggs are scrambled, the mechanism that transforms the liquidy beaten eggs into a fluffy mound on the plate is protein coagulation—the process by which, when exposed to heat, proteins unfold and then tangle up with one another and set, forming a latticed gel. The more tender the scrambled eggs, the more loosely the proteins have coagulated. Adding water to scrambled eggs dilutes the proteins a little, thereby raising the temperature at which they coagulate and making it harder to overcook the scramble. Water also increases the amount of steam, which puffs up the eggs, producing fluffy scrambled eggs. As for milk, it contains water but also fat, which coats the protein molecules so that they can’t bind with one another as tightly. The key to scrambled eggs that are both fluffy and tender is a balance of water and fat.

We scrambled eggs with water, milk, half-and-half, and heavy cream and found that half-and-half provided the best balance of fat and water when we used our favorite scrambled egg formula: two additional yolks for every eight eggs to boost richness. When we simply scrambled whole eggs without the benefit of the extra fat from the yolk, some tasters preferred the eggs made with heavy cream.

The bottom line: Scrambled eggs benefit from added liquid, preferably a liquid with fat; use 1 tablespoon of liquid for every two eggs. For fluffy and tender scrambled eggs for four, use eight eggs, two yolks, and ¼ cup of half-and-half.

2. Is it true that freshly laid eggs have different baking properties than older supermarket eggs?

Because egg whites thin with age, some bakers theorize that the weakened proteins of eggs even a few weeks old can stretch more than those from just-laid eggs, leading to cakes that rise higher and have a softer, more tender texture than cakes made with the freshest eggs.

To test this theory, we made our Fluffy Yellow Layer Cake with 7-week-old supermarket eggs (we determined their age by the date on the carton) and eggs from a Vermont farm laid a few days before. Any differences we found were slight. The cake made with store-bought eggs dissolved a little more quickly on the tongue, and the cake made with the farm-fresh eggs was a little more “toothsome.” But only a few tasters actually detected these variations in texture. Did one cake rise higher than the other? No.

The bottom line: Don’t pass up farm-fresh eggs in hopes of baking a better cake—age doesn’t matter. Besides, you’re probably just as likely to scramble or fry your eggs, dishes where freshness truly matters.

3. Is there really a difference between the different grades of eggs?

The USDA labels eggs either AA, A, or B according to their shell appearance and the quality of the egg inside. A misshapen or thin shell typically merits the lowest B grade, and such eggs are usually used commercially. To distinguish AA from A, graders use a method called candling: Each egg is held up to a bright light in a dark room to check the interior quality. Grade AA eggs have whites that are so thick that the firm yolk is hard to see; grade AA eggs are rare (and more expensive) in supermarkets. Grade A eggs have slightly looser whites and softer yolks; this grade accounts for most of the eggs sold in supermarkets across the country. Both are acceptable in any application.

4. How are eggs pasteurized? Can they be substituted for normal unpasteurized eggs?

In rare cases, eating raw egg (in cookie dough, homemade mayonnaise, etc.) can result in the bacterial infection salmonella, but pasteurized eggs promise a safer alternative. Whole, in-the-shell eggs are pasteurized by going through a succession of heated water baths (warm enough to kill bacteria, but not so warm as to cook the eggs) before being chilled and waxed so that the porous shells cannot be re-contaminated.

To see how pasteurized eggs stacked up to the unpasteurized variety, we made Caesar dressing with both pasteurized and unpasteurized raw yolks, and meringues from the whites of each. We didn’t notice any differences in the two dressings, but that was not the case with the meringues. We immediately noticed that the pasteurized whites were much looser and more watery than their unpasteurized counterparts. What’s more, the pasteurized whites took more than twice as long to whip into a stiff and glossy meringue. Once whipped, both meringues had a similar texture and flavor. Curious how the two varieties compared when cooked, we fried, scrambled, and baked each type of egg in a cake and found no differences in flavor or texture. Pasteurized eggs are a suitable substitute for regular eggs, but pasteurized egg whites will take more than twice as long to whip.

5. Do brighter yolks mean fresher eggs?

No. The yellow color of egg yolks comes from plant pigments called xanthophylls that the hen gets from her food. The color of an egg yolk depends on what the hen eats; alfalfa and corn feeds provide more of the yellow pigment than barley or wheat feeds do. Some egg producers add marigold petals or other additives to chicken feed to deepen yolk color, so deep golden yolks may not be reliable indicators of the diet of the layer. There is one visual cue, however, that clearly indicates the freshness of cracked eggs: their posture. Cracked fresh eggs stand up straighter and spread less than do older eggs.

The color of the yolk has nothing to do with freshness and everything to do with the hen’s diet. Fresh eggs, however, have taller yolks and tighter whites than older eggs.

6. Most recipes call for adding eggs one at a time to creamed butter and sugar. Would adding the eggs all at once really make a difference?

Looking into our archives, we noticed that almost all of our cake and cookie recipes that call for more than one egg either add them one at a time or premix the eggs and then add them in a steady stream. We wondered why this extra effort is involved and whether it is necessary. First, we made a batch of our Chocolate Chip Oatmeal Cookies. When the two eggs in the recipe were added one at a time, it took about 30 seconds to incorporate each into the creamed butter and sugar, compared with slightly over two minutes when both were added at once. While the difference in time might not seem significant, the difference in the finished cookies was. Eggs added one at a time led to cookies that were thick and chewy; eggs added all at once produced cookies that spread, became unevenly shaped, and were not as chewy. We encountered similar differences with our Chocolate Sour Cream Bundt Cake and Classic Pound Cake. In both recipes, when the eggs were added together, it took longer to incorporate them and the cakes turned out denser and slightly rubbery.

The fact is, like oil and vinegar, eggs and butter don’t mix naturally. It’s a matter of chemistry: Butter is at least 80 percent fat, while eggs contain large amounts of water. So any time you add more than a single egg to creamed butter, it’s best to do it slowly to give the mixture time to thicken and emulsify.

7. Omega-3 fatty acids are said to reduce blood pressure and the risk of coronary disease as well as relieve stress and depression—but how do the omega-3 eggs taste?

Here’s the latest from the henhouse: eggs with a high level of omega-3 fatty acids. This unsaturated fat, also found in fish oil, is said to reduce blood pressure and the risk of coronary disease as well as relieve stress and depression. That’s all well and good, but how do the eggs taste? We set up a blind tasting of eggs containing levels of omega-3 from around 50 mg per egg (the standard amount in ordinary supermarket eggs) up to 310 mg per egg. Our finding: The more omega-3’s, the richer the egg flavor and the deeper the yolk color. Why? Commercially raised chickens usually peck on corn and soy, while chickens on the omega-3-enriched diet have supplements of greens, flax seed, and algae, which also add flavor, complexity, and color.

When shopping for a good egg, buyer beware: Brands may claim a high level of omega-3’s, but the fine print sometimes reveals that the number refers to the level present in two eggs, not one. Look for brands that guarantee at least 200 mg per egg.

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