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November 2007

How to Separate Egg Whites and Yolks

What is the best way to separate eggs into the whites and yolks?

--Janet

There are three ways to separate whites from yolks.  The first way is using a commercially available egg separator.  These devices have a cup supported by rigid spokes in the middle of a ring.  You crack the egg and let the contents drop into the center of the separator.  If you do it right, the yolk will stay unbroken in the cup while the whites flow through the open spaces into a bowl underneath.

The next way is to crack open the egg and gently pour the yolk back and forth between the two halves of the shell.  As you do this, tip the shell halves somewhat so that the white is allowed to flow over the edge and into the bowl below.

 

The third technique is to start with very clean hands and simply crack the egg and empty the contents into the cupped fingers of one hand which is held over a bowl.  The whites are allowed to flow between your fingers into the bowl.

To crack an egg, gently but firmly rap the mid-point of the egg, between the pointed and blunt ends, against the rim of a bowl.  With practice you will learn just how hard to hit the egg so that the shell is opened a bit and cracked a bit of the way around its equator.  Now, hold the egg bu the shell either side of the crack and gently pull and bend it away from the crack so that the shell splits.  Try not to dig your thumbs into the crack for leverage, as this may push bits of shell into the egg white or break the yolk.  With some practice, you can even learn to split the cracked shell open with one hand, which is useful for the third method, above.

There is a current pretense in cooking nowadays to tell people they should crack the egg on the counter top, as this supposedly reduces the chance of bits of shell getting into the food.  Since I have never had a big problem using the method described above, I fail to see why the counter method would work better.  In either case you are cracking the shell so the risk of fragments will always be there.  With fresh eggs, where the membrane under the shell is still adhering firmly to it, bits of shell are held by the membrane and don't usually end up in the food.  Still, it is good to give one final check before using the egg whites or yolks and remove any pieces of shell that might have slipped by.

If you are planning to beat the egg whites, it is a good idea to break your eggs one at a time, using three bowls: a small one to catch the white as each egg is broken; a second one that the whites are put into one at a time; and a third for the yolks.  After each egg is separated, make sure that the yolk remained intact.  If it broke, inspect the white to make sure there is no yolk in it.  If there is, you can frequently dab the yolk out with the corner of a paper towel, provided there isn't too much.  Otherwise, discard the white, wipe out the catch bowl and crack another egg in its place.  Even the tiniest bit of yolk can cause problems in beating egg whites.

Finally, the proverbial question of what to do with the chalaza, that white rubbery material that is attached to the yolk.  The chalaza is like a twisted elastic band that holds the yolk roughly in the center of the egg.  Generally, you can leave it attached to the yolks.  If they are being used to make a custard or other smooth sauce, a final straining will remove any lumps of chalaza from the mixture.


If you have food or cooking questions, send them to Questions@KitchenSavvy.com
Due to the volume of questions received, not all can be answered.
© Lost Hobbit Enterprises 2004 onward





Due to the volume of questions received, not all can be answered, nor can we guarantee we will answer questions immediately
© Lost Hobbit Enterprises 2004 onward


Expiry Date on Baking Powder

I notice my baking powder had 2/04 dated on bottom of the can. I assume this is the expiration date. I'm in the middle of mixing ingredients for cake. How could I substitute with baking soda or is it safe to still use it?  Thanks in advance.

--Dianne

 

The expiry date on baking powder is there because it loses some of its strength over time.  While the bicarbonate of soda (baking soda) component of baking powder is fairly stable, the acidic ingredient may be less so, and may break down over time especially if exposed to heat or humidity.  Because of this, the strength of your baking powder decreases over time.  Also, slowly over time, the chemicals in baking powder combine.  Humidity from the air causes them to react in the same way they do when mixed in a batter.  For this reason, most commercial baking powder has a shelf life of around a year.

According to Cook's Illustrated, you can test the strength of your baking powder by mixing a half teaspoon into a cup of tap water.  It should fizz vigorously.  This will only work with fast-acting or double-acting baking powder, however.  Slow-acting baking powder reacts poorly at room temperature (see Baking Soda vs. Baking Powder for the differences).

Since the expiry date on your package is over a decade old, the chances are that the baking powder will be extremely weak.  You can mix a substitute for baking powder, if you have baking soda and cream of tarter on hand.  If a recipe calls for 1 teaspoon of baking powder, that can be replaced by ¼ teaspoon of baking soda and ½ teaspoon of cream of tartar.  Some cooks also add  ¼ teaspoon of cornstarch to make up the same volume, although that isn't strictly necessary.


If you have food or cooking questions, send them to Questions@KitchenSavvy.com
Due to the volume of questions received, not all can be answered.
© Lost Hobbit Enterprises 2004 onward





Due to the volume of questions received, not all can be answered, nor can we guarantee we will answer questions immediately
© Lost Hobbit Enterprises 2004 onward


You've Got to Know When to Fold 'em

I was planning to make a Pumpkin Mousse for Thanksgiving.  My recipe says to fold the whipped cream into the pumpkin mixture.  What does it mean to 'fold' something, and when do you use this technique?

--Laurel

In cooking, folding is a mixing technique that is used to gently combine ingredients where a more aggressive method would cause one of the ingredients to lose volume.  Commonly, the ingredient that is of concern is either whipped cream or beaten egg whites. The lighter ingredient, in this case the whipped cream, is put into a bowl already containing the heavier one, the pumpkin mixture.

 

To fold them together, cut down through the center of the ingredients with the edge of a spatula until it touches the bottom of the bowl, near to you.  Then turn your wrist until the spatula is parallel to the bottom of the bowl.  Lift, continuing to turn the spatula so that the ingredients on the bottom are brought gently up and folded over top of the mixture.  In total, the blade of the spatula will make three quarters of a rotation.  If you are right handed, usually you will rotate the spatula clockwise while sweeping it in a right to left, again clockwise, direction.  After each fold, use the other hand to turn the bowl one quarter turn and repeat until the ingredients are evenly mixed, using as few folds as possible.

The gentle motion of folding will blend the ingredients without beating air out of the mixture, as would happen with, for instance, a whisk.

Some instructions will say to make a figure eight pattern while moving the spatula into the bowl before each fold.  This isn't really necessary.  With a little practice, folding ingredients will become quite easy.


If you have food or cooking questions, send them to Questions@KitchenSavvy.com
Due to the volume of questions received, not all can be answered.
© Lost Hobbit Enterprises 2004 onward





Due to the volume of questions received, not all can be answered, nor can we guarantee we will answer questions immediately
© Lost Hobbit Enterprises 2004 onward


Care of Copper Pots

I have what I believe to be a copper pot.  At least it has copper on the outside.  I've cooked pasta in it many times and it works great.

However, once I kept the leftover pasta in the pot and put it in the fridge.  A day or two later when I took the pasta and pot out of the fridge, the pasta was discolored…I think it was green.  But the pasta smelled fine, and certainly gave no indication that it was spoiled.

Is this some sort of a chemical reaction?  Is it dangerous?  Is there something I can do to prevent this?

--Daniel

 

Copper pots that are not just for show are copper on the outside, but lined with another metal on the inside.  The reason for this is that copper itself is toxic.  According to McGee, the issue isn't necessarily the amount of copper taken into the diet as the fact that the human body has a limited capacity to excrete copper so that if the intake is higher than what can be eliminated, copper will build up in the the body.   Copper toxicity causes nausea, vomiting, abdominal pain, metallic taste, and diarrhea. Ingestion of large doses may cause stomach and intestine ulceration, jaundice, and kidney and liver damage.  Copper is also needed by the body in small amounts for enzyme production.  The USDA dietary guidelines for copper are a Recommended Daily Allowance (RDA) of 900 micrograms and a maximum daily upper limit of 10 milligrams.

The pot you have is more than likely copper lined with tin.  Stainless steel is also sometimes used to line copper pots, though less commonly.  Don't confuse this, though, with stainless steel pots that have a copper coating on the outside.  Tin is most commonly used to line copper, although it is prone to wear, has a low melting point and shouldn't be used with acidic foods.

The fact that leftover pasta cooked in the pot has turned green suggests that the tin lining on your pot is scratched or worn through, and that some of the copper is leeching into the cooking water.  As the pasta sat afterward, the copper reacted with chemicals in the food, most likely sulfur compounds, causing the characteristic green tint.

If you have tin lined copper pots, they should be inspected frequently for scratches or areas of wear that will allow the food being cooked, or the cooking liquid, to come into direct contact with the underlying copper.  If the lining looks worn or deeply scratched, check with kitchen supply stores or on the Internet for re-tinning services.

Metal utensils should never be used in copper pots lined with tin, as the tin scratches easily.  Only use plastic or wooden utensils.  Avoid overheating copper pots or placing them empty on the stovetop to preheat, as this can cause the tin lining to melt.  Wash by hand using a mild dish detergent, never an abrasive cleaner or scouring pad, as these can wear down the lining, too.  To clean the outside, use a commercial copper cleaner following instructions, or a soft cloth dipped in a paste made with vinegar and table salt.  As mentioned earlier, don't use tin lined copper pots to cook acidic foods such as tomato based sauces.  And, as you might have guessed, don't use copper pots or bowls, lined or unlined, to store food.

Copper pots or pans that are not lined with tin or stainless steel are for decorative use only and should not be used for cooking.  The one exception is that some cooks prefer to whisk egg whites in a copper bowl as it helps produce firmer peaks.  The small amount of copper that enters food through this application is not sufficient to be considered a concern.

As for the safety of the pasta you cooked, it is hard to say.  A small amount of copper is useful in the diet, but how much is in the pasta is anyone's guess, as is the amount that might have already entered your body through other foods cooked in this pan.  The first rule of safety in the kitchen is "When in doubt, throw it out!"  That's what I would do with the pasta in this case.


If you have food or cooking questions, send them to Questions@KitchenSavvy.com
Due to the volume of questions received, not all can be answered.
© Lost Hobbit Enterprises 2004 onward





Due to the volume of questions received, not all can be answered, nor can we guarantee we will answer questions immediately
© Lost Hobbit Enterprises 2004 onward