KitchenSavvy

Pop-up Turkey Thermometer

This past Christmas we bought a turkey with one of those plastic pop-up thermometer thingies in it.  It got me to wondering:  How do these things work, are they reliable, and can they be reused?

--George

Although some people refer to them as timers, they are actually thermometers, as you note, since they indicate the temperature of the meat and not how long it has been cooking.  If you look inside one of them, you will see the pop-up plunger, usually red plastic, inside the housing.  The end of the plunger is held in place by a small glob of metal that is made to melt at a temperature very close to 165°F (74°C) plus or minus one or two degrees F (a half to one degree C).  Once the metal blob has melted, a spring inside the device lifts the plunger up to indicate that the turkey is cooked.

While the temperature at which they will pop can be determined quite accurately, they have two shortcomings.  First, they are fixed in length so they only penetrate a fixed distance into the meat.  Since the breast of a turkey isn't always the same thickness, the sensor end of the pop-up may not be placed far enough in on a larger turkey, or may be too close to bone on a small one.

Also, they only measure the temperature at one spot on the bird.  If it has cooked unevenly, or if it was frozen and thawed unevenly, the pop-up may give a wrong reading.  As note in Roast Turkey Temperature, the meat of a turkey turns out best when cooked to 165°F (74°C) for the breast and between 175°F (80°C) and 180°F (82°C) for the thigh and drumstick.

For these reasons, it is recommended that you check the temperature in several places using an instant read thermometer to be sure that everything is cooked right.

As far as reusing them, while some people suggest that this can be done, it may be difficult to assure that the end of the plunger is properly fixed back into the metal so that it won't release too early.  Since they come with the turkey, or can be purchased new for about a dollar each, the question is whether your health, and that of your family or friends, is worth the risk.

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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

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.

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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

Blending Hot Liquids

Why is it that when you blend hot liquids they blow the lid off the blender if you aren't holding it in place?

--Dave

Actually, the science of this is pretty straight forward.  As you know, when you heat a gas, it expands.  So, you put hot liquid into the the jar of the blender and put the lid on.  At this point you have a near boiling liquid with some near room temperature air between it and the top of the jar.  When you start the blender, the air is pulled down through the liquid into the blades where it is broken into millions of tiny bubbles.  At the same time, all of that air gets heated up and expands to about a quarter again the volume it had before^*.  Because some of it is incorporated into the liquid, the effect of the expanding air is to push the liquid upwards.   Both the now hot air above the liquid plus the expanding liquid force the lid off the container.

In order to be safe, it is recommended when you blend hot liquids that you never fill the jar more than half full, that you put the lid on and then cover it with a dry towel and hold it down by hand.  Also, use as slow a speed as possible.

^* If you are interested in a more scientific explanation, the basic equation that describes the relationship between pressure, volume and temperature of a gas is PV=nRT, where:

P is the pressure of the gas;
V is the volume it occupies
n is the amount of the gas there is;
R is a scientific constant; and
T is the temperature of the gas in degrees Kelvin.

Kelvin is a temperature scale that has the same scale as Celsius, except that 0°K is the absolutely lowest temperature that anything can possibly reach.  0°K is the same as -459.67°F or -273.15°C.  What the formula says is that if you double the temperature, either the volume will double, the pressure will double (if the gas is tightly contained), or some combination of the two will occur.

So, the air in the blender jar is at room temperature, which is about 293°K.  You turn on the blender, and all of a sudden it is heated to around 373°K.  Assuming that the pressure tries to stay the same, which it will do if possible since the container has a lid that can be blown off, the gas expands by 373/293 = 1.273 times.

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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

Brewing Coffee

There are so many appliances available nowadays to make coffee.  What is the best way to brew coffee in order to get the best flavor?

--Sylvia

If you like a smooth well flavored coffee without a lot of bitterness, then you want to use water that is just off the boil, somewhere around 200°F (93°C), give or take about 5°F (3°C).  Much cooler and the flavors aren't extracted from the coffee; much warmer and too much tannin and other compounds are extracted, making the coffee harsh.

Drip coffee machines typically heat the water from the reservoir in a pipe built into the heating pad under the pot.  Steam from the heated water pushes it up a tube and into the basket containing the coffee grounds.  Depending on the make and design, some of these may work well, but with others the water may be far too hot.

The traditional coffee perk, which pushes water up a central stem where it flows over into the basket holding the grounds, has two major faults.  First, because of the closed design the water is far too hot when it comes into contact with the grounds, especially toward the end of the brew cycle.  Second, because the water is recirculated, the already brewed coffee is returned to the boiling point repeatedly making the final product more bitter.

My personal favorite for making coffee is the French Press.  Ground coffee is placed into the container of the press and water that has been boiled and then allowed to cool slightly is poured over the grounds.  The mixture is stirred to make sure the coffee is fully in contact with the water, and then the cover is put on.  Built into the cover is a plunger.  After the coffee has sat for two to four minutes, the plunger is slowly pressed down, forcing the grounds to the bottom and extracting the brewed coffee which is poured immediately.  The result is a very smooth and flavorful cup of coffee.

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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

Difference Between Dry and Liquid Measuring Cups

Hi.  Is there any difference between dry and liquid measuring cups?  Do they measure the same amount, and if so, why do I need both?  I had heard once that there is a difference between the volume of dry and liquid measures.

--Bob

The volume measured by dry and liquid measuring cups typically used in the kitchen is the same.   To be clear, I am using the word "cup" here to mean the container and not necessarily the unit of measure, so the same holds true for measuring a half cup, or quarter cup, using the appropriate sized measure.

The reason for having two sets is because dry ingredients are easiest handled using a "scoop and level" technique where the cup is overfilled and then a knife or other straight edge is scraped across the top to level the amount to the right measure.  This only works if the measuring cup is filled to the brim.  If you try to measure a cup of, say, sugar using a liquid measuring cup you can't scoop and level, and it is harder to get an accurate measure by using the line.  Dry ingredients don't want to make a  nice straight line across their top and if you try to get them to, they settle in the cup causing error, so the cup used for liquid measures is not accurate for dry ingredients.

Conversely, it is difficult to measure  liquid if you need to fill the measuring cup to the very brim, and even if you succeed, you either make a mess or have difficulty getting the entire amount transported to the next step, so dry measuring cups are not easy to work with for liquid ingredients. 

In the U.S., the quantity measured by dry and liquid measured less than a pint are the same.  After that, there is a difference.  A U.S. pint used for liquid measures is 473 milliliters, where as a dry measure pint is 551 milliliters, which means it is 16.5% larger.  A U.S. dry measure quart is 16.4% bigger than its liquid counterpart, at 1101 milliliters vs. 946.

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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

Meat Dries Out in Slow Cooker

I've just started using a slow cooker, and have had pretty mediocre results in keeping my meat moist vs. conventional cooking. For example, the chicken always seems overdone and dry.  Even my beef stew has been on the dry side, with my latest one almost inedible (not tough--just dry) after 7.5 hours on Low. My question is:  Am I simply overcooking it (i.e. the slow cooker might be hotter than the recipes call for)?  Should I start adjusting my times down, and if so, by how much?  Or is it meant to be stewed longer?  Should I add more liquid?  The vegetables seem perfect, though.

I've actually used several different models of slow cooker (some borrowed, some bought and returned), and they all seem to dry the meat.

-- Ramona

This may come as a surprise, but what is likely happening is that you are overcooking the meat.  We tend to think that if you stew meat, the longer it cooks, the more tender and juicy it gets.  In fact, this works only up to a point.

As proteins heat up, they loosen their internal bonds, begin to uncoil and bond with neighboring protein molecules.   See Custards and Sauces for a description of how proteins change with temperature.

However, at somewhere around 170°F (76°C), depending on the meat used and the other ingredients present, the protein network begins to break apart again and and the individual molecules tighten back up.  As that happens, the muscle fibers in the meat shrink, their cell walls break open and the water that was trapped within the muscle fiber starts to leak out. The result is that the texture of the meat becomes dry even though it was cooked in liquid.  The same thing can happen in a pot roast or even with meat dishes cooked on the stovetop.

If you're like many people who start supper in the slow cooker before you leave for work in the morning then you are taking part in a balancing act.  You are trying to cook the food at a sufficiently high temperature so that it gets out of the danger zone for bacterial growth fairly quickly.  That temperature range is between 40°F and 140°F (4°C to 60°C).  On the other hand, you don't want to overcook the meat to the point of being too dry. This isn't an easy balance to achieve.

Just to clarify here, based on the comment below from Catt, 140°F (60°C) is the top end of the danger zone through which you want the heat to rise quickly.  In order to kill salmonella and other pathogens, you need to cook until the center of the meat is at least 165°F (74°C).  While protein starts to tighten around 170°F (76°C), it doesn't become unpleasantly dry until around 185°F (85°C), so between 165°F and 185°F (74°C and 85°C) is the target range, if you are measuring.  I would shoot for around 175°F (79°C).

I would try cutting the meat into somewhat larger chunks, perhaps up to about 2 inches (5 cm) to a side, and cooking for a shorter period of time.  Once the cooker gets up to temperature, try cooking the food for about 5 hours longer.  That should give you a total cooking time of about 6 hours.  If the meat is still coming out dry, reduce the time by another half hour or so.  For safety, though, always be sure that the meat is cooked completely.

If you want to see more recommendations on using a slow cooker check out the posting Browning Meat for Slow Cooker.

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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

Browning Meat for Slow Cooker

Please help settle a family debate.  Is it necessary to brown meat that is being cooked in a slow cooker?

-- Sandra, Bobbi and Bruce

With the exception of ground meats, it is not absolutely necessary to brown the meat before cooking it in a slow cooker or Crock Pot, although it is recommended as part of the flavor development of the dish.  When meat is browned, the sugars and proteins on the surface undergo a change called the Maillard reaction, after the French physician Louis Camille Maillard (pronounced "My yard") who discovered the reaction.  This reaction creates the rich nutty flavor associated with gravies, roasted meats, baked beans, and other foods.

If you don't brown the meat, particularly in beef dishes, then the final dish ends up tasting rather thin and without depth.  In slow cooker recipes using  chicken and pork, where the flavors are not usually so complex, browning is not as common.  Still, the dishes may benefit from browning the meat.

Because ground meats are more prone to growth of e-coli and other bacteria, I would recommend always browning them.

The USDA Food Safety and Inspection Service recommends these practices for using slow cookers:

• Begin with a clean cooker, clean utensils and a clean work area.
• Wash hands before and during food preparation.
• Keep perishable foods refrigerated until preparation time.
• If you cut up meat and vegetables in advance, store them separately in the refrigerator.
• Always defrost meat or poultry before putting it into a slow cooker.
• Choose to make foods with a high moisture content such as chili, soup, stew or spaghetti sauce.
• Cut food into chunks or small pieces to ensure thorough cooking. Do not use the slow cooker for large pieces like a roast or whole chicken because the food will cook so slowly it could remain in the bacterial "Danger Zone," between 40 °F and 140 °F (4 °C to 60 °C), too long.
• Fill cooker no less than half full and no more than two-thirds full.
• Vegetables cook slower than meat and poultry in a slow cooker so if using them, put vegetables in first, at the bottom and around sides of the utensil. Then add meat and cover the food with liquid such as broth, water or barbecue sauce.
• Keep the lid in place, removing only to stir the food or check for doneness.
• If possible, turn the cooker on the highest setting for the first hour of cooking time and then use setting called for in your recipe. However, it's safe to cook foods on low the entire time -- if you're leaving for work, for example, and preparation time is limited.
• Once it is done, food will stay safe as long as the cooker is operating.
• If you are not at home during the entire slow-cooking process and the power goes out, throw away the food even if it looks done. If you are at home, finish cooking the ingredients immediately by some other means: on a gas stove, on the outdoor grill or at a house where the power is on. If the food was completely cooked before the power went out, and you were home at the time so you know when it happened, the food should remain safe up to two hours in the cooker with the power off.

I would add that if you are cutting up meat and vegetables ahead of time, cut all of the vegetables first and package them up to refrigerate before starting to cut up the meat, to avoid cross contamination.

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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

In a Jam

This summer we canned mango jam.  Now, about two months later, we noticed that all the jars have discolored fruit at the top.  We followed instructions for the recipe and filled the jars 1/4 inch from the top and placed them in a water bath canner for a full ten minutes.  The fruit has settled a bit and now there seems to be more space between the lid.

I have read that discoloration is probably due to either not filling the jar to the desired level or not processing long enough.  We did both of these according to the instructions.  What could have happened and should we throw all of our jam out?  We wanted to give some away as gifts but they do not look nice anymore.   We will keep some of them if it is still safe to eat.

-- Kiyo

I checked with Jarden Home Brands, marketers of Ball and Kerr brand home canning products, regarding this question.  Here is what they advised:

"Food darkening in the top of a jar can be caused by the food not being processed long enough to destroy enzymes.  Another cause can be that too much air was left in the jar due to the headspace.  Air left in jars permits oxidation.  Since the consumer stated there was some settling of the jam, this seems to be the likely cause.

The consumer did not mention if the jars had good vacuum seals.  Leaving too much air inside the jar may lead to a low vacuum seal or no seal at all.  If the seal has broken on these jars, the contents should be discarded.

Products that darken at the top of a jar is not necessarily a sign of spoilage.  Unfortunately, we have not tested a mango jam recipe.  We are unable to say a recipe is safe if we have not tested it."

Testing Your Metal

Q: I'd heard that metallic things like knives or blades will reduce the content of enzyme in fruits or vegetables.  Is that true?

-- Philip M.

I have not heard of any evidence to support this.  In fact, the usual belief is quite the opposite, that cutting fruits or vegetables with a steel knife will cause them to turn brown.  A common claim is that cutting leafy vegetables, like lettuce, will make them turn brown quicker than if you tear them by hand.  Explanations are that the knife reacts with the food to turn it brown, or that cutting damages the cells of the leaf, or that it causes more bruising.

Proponents of ceramic knives say that their knives don't react with foods the same way that steel knives do.

Blind Baking

Q: What does the term "blind baking" refer to?

When making pastries, tarts, flans, quiches or other items with a crust, it is sometimes necessary to bake the shell before the filling is put in.  This helps prevent the filling from making the crust soggy or keeping it from cooking completely.  It also allows you to cook the crust at a higher temperature in order to have it turn out light and flaky and then cook the filling at a lower temperature so that it doesn't overcook.  This is particularly useful for custard pies (see "Custards and Sauces").