Cooking for Geeks: Real Science, Great Hacks, and Good Food (11 page)
Read Cooking for Geeks: Real Science, Great Hacks, and Good Food Online
Authors: Jeff Potter
Tags: #COOKING / Methods / General
They get narrower, and they get shorter. People find different applications for them. The poultry industry still does that. What I’m talking about is mostly pre-WWII. After WWII, people started coming to us and saying, “Hey, can’t you make this shape from scratch?” So we started to create the same shape as the worn-out knife. You wouldn’t have to wear out a giant cimeter; you could just buy a breaking knife off the shelf. A lot of our traditional knife shapes have evolved from large blades that were worn down and used for different applications, and then we started making a blade with that shape.
What advice would you give somebody new to the kitchen?
If I were being a smartass, I would tell you don’t run with a knife. Keep your knives out of the dishwasher. Wipe them clean with a damp rag. When you put them in the dishwasher, they bang together and you nick up your edges. If you do put them in the dishwasher, make sure you pull them right out of the basket and dry them off. Keep up with your sharpening; don’t let your knife get dull. Maintain the edge every time you use it or every other time you use it. Give it one or two strokes on a steel and sharpening will never be a chore, and you will always have a sharp knife.
Keeping your knives sharp is the kitchen equivalent of backing up your files: it’s something you should do more often than you think. A sharper knife is safer and easier to use:
- Sharp knives require less pressure for making cuts so there’s less force involved — meaning you’re less likely to slip and cut yourself.
- Sharp knives cut cleaner; there is less “tear” through whatever you’re cutting.
- Sharp knives keep your arm from getting tired because you don’t have to muscle through things. Of course, you’d probably need to be slicing and dicing for many hours to notice.
Keeping your knives in good working order involves both keeping the blade “true” (in alignment) and grinding down the blade to reshape the edge if the trued shape is lost. To keep your knives true, use a sharpening steel (those steel rods ubiquitous in celebrity chef photos) as part of your cleanup and wash routine at the end of a cooking session. By running the knife against the sharpening steel, you push any portion of the edge that is out of alignment (“burrs”) back into alignment. (
Never
try to true a serrated knife, such as a bread knife — the sharpening steel won’t fit against the serrated edge.) Look for a diamond-coated sharpening steel; the diamond coating is harder than the steel, so it can not only realign the burrs but also create a new edge, keeping the knife truly sharp and actually removing the need to reshape the edge.
More serious sharpening involves grinding down the blade to form a new edge and can be done against any hard surface: a sharpening stone, a grinding wheel, even a brick! (See the interview with Buck Raper on the preceding pages for details.) If it comes to that, I find it easier to have my knives professionally sharpened. Grinding down the edge isn’t a great thing, though, because creating the new edge removes material. Knives used in restaurants can be “sharpened through” in under a year — that is, sharpened down to a point where the new edge on the knife becomes too thick to hold a sharp edge for long.
Most cutting boards are made of either hardwoods, such as maple or walnut, or plastics like nylon or polyethylene. Regardless of which type you get, look for ones that are at least 12” × 18” / 30 cm × 45 cm. Bigger is better, as long as the board fits in your sink or dishwasher. If you choose a plastic board, consider snagging both a rigid one, which can serve double duty as a serving board, and a thin, flexible one, which can be used as a makeshift funnel (e.g., chop veggies, pick up board, and curl it while sliding the food into your pan).
You can use the wrapping paper that some meats come in as an impromptu disposable cutting board if you are just cutting something like a sausage to sauté. One less dish to wash!
Always use two different cutting boards when working with meats: one for raw meats and a second for cooked items. I use a plastic cutting board for raw meats and a wooden one for after cooking because I find the difference in material to be an easy visual reminder. I then toss the plastic cutting board into the dishwasher for cleanup. Since I have more than two boards, I use the plastic one exclusively for raw meats.
Plastic cutting boards have the advantage of being sterilized when washed in a dishwasher because the heated water kills common bacteria. (Don’t put your wooden cutting board in the dishwasher, though: the hot water will damage the board.) Note that washing a cutting board in the sink with hot water and soap is
not
sufficient to remove absolutely all traces of bacteria like
E. coli
. Whether wood or plastic is “safer” depends on your habits. Some studies have shown that wood is better than plastic at preventing cross-contamination, possibly due to chemical properties of wood, which suggests that wooden cutting boards are more forgiving to lapses in sanitization. If you don’t have a dishwasher, current research suggests that a wooden cutting board is the way to go.
Researchers at UC Davis found that disease-related bacteria such as
E. coli
survived for a longer period of time on plastic cutting boards than wooden ones, and that treating wooden cutting boards with mineral oil did not materially affect the die-off rate. Additional research found that home chefs using plastic cutting boards are twice as likely to contract salmonellosis than those using wooden cutting boards, even when cleaning the board after contact with raw meat.
Here are a few additional tips:
- Place a bar towel or slip mat under your cutting board to prevent it from moving while you’re working.
- Some cutting boards have a groove around the edge to prevent liquids from running over the edge. This is handy when you’re working with wet items, but it makes transferring dry items, such as diced potato, more difficult. Keep this in mind when choosing which board — or which side of a board — to use.
- You can clean wooden cutting boards by wiping them down with white vinegar (the acidity kills most common bacteria). If your board smells (e.g., of garlic or fish), you can use lemon juice and salt to neutralize the odors.
- Prep vegetables and fruits before starting to work on raw meats. This further reduces the chances of bacterial cross-contamination.
Which pot or pan is ideal to use for cooking an item, and how the materials in that pot will affect the cooking process, is a topic that could easily be expanded to fill an entire chapter and yet still leave questions unanswered. When it comes to the metals used in making pans, there are two key variables: how quickly the metal dissipates heat and how much heat the metal can retain (see
Metals, Pans, and Hot Spots
). For new cooks, the biggest issues are avoiding hot spots and being careful not to overheat the pan. Avoid hot spots by using pans with materials that conduct heat well (and avoid those really cheap thin pans). Also, don’t just automatically crank the heat up to high. Hotter doesn’t mean faster! And if you do find yourself with a pan full of ingredients that are starting to burn, dump the food into a bowl to halt the burning. Even off the burner, the pan will still be hot enough to continue cooking and burning its contents.
All that being said, don’t obsess over the “perfect” pan for a job. Looking at cladded pans (two types of metals sandwiched together) and can’t decide between copper and aluminum? If they’re properly made (in terms of the thickness of the metal and the construction), there won’t be a huge difference. Same thing when it comes to size and shape.
Sure, to a professional it matters: cooking 10 pounds of onions in a narrower pot will yield more consistent results than cooking them in a wide, shallow pan (the narrower pot will retain water better, which assists in the cooking). But as a home chef, you’ll typically achieve similar results in both cases, as long as you use common sense about the amount of heat you’re using and keep a watchful eye on the pan.
As with knives, let your preferences and cooking style guide your selection of pots and pans, and be willing to experiment and replace items to suit your needs. Avoid purchasing a set of pots and pans, because sets often come with extra items that aren’t quite ideal and end up wasting space and money. Instead, select each pot or pan individually and purchase only the ones that best suit your needs. Browse your local restaurant supply store or search for commercial products online. Commercial frying pans are cheap multitaskers. If you’re going to splurge on a pot or pan, spring for an enameled cast iron pan (Le Creuset is the leading maker), a good skillet, or a sauté pan.
A skillet is technically the same thing as a frying pan, but I think of frying pans as being the cheap-but-good commercial aluminum ones and skillets as being stainless steel. A sauté pan is like a skillet, but the inside corners are square instead of rounded up.
When using pots and pans, follow these tips. Unless you’re heating a pan to sauté something, don’t absentmindedly leave it empty while it’s heating on the burner. Overheating a pan, especially the nonstick type, will ruin the pan’s finish and possibly warp it. Cast iron is the exception, but you still risk destroying the seasoned finish. Also, if you’re anything like me, when you throw a dinner party the dishes often wait until the next morning. Don’t leave pots and pans soaking in water overnight. In some cases, the water can get “under” nonstick finishes and blister it. In the case of cast iron, the pans will rust.
Frying pans.
A frying pan is a shallow, wide pan with slightly sloped edges. Look for frying pans that have a smooth cooking surface and are as large as your stovetop will comfortably accommodate. If you get one that’s too large, the burners on your stove will heat the center but not the outer region, which will lead to uneven cooking.
Nonstick frying pans are useful for sautéing fish and for breakfast items such as eggs, pancakes, or crepes. Using a nonstick pan for eggs or fish also allows you to reduce the amount of butter or oil needed during cooking.
Since nonstick coatings prevent the formation of fond (the bits of food that brown in the bottom of the pan and provide much of the flavor in sauces), you might also want to purchase a stainless steel frying or sauté pan.
How do they get Teflon (polytetrafluoroethylene, PTFE) to stick to the pan if it doesn’t stick to anything?
By using a chemical that can actually stick to both PTFE and the pan, called an
adhesion promoter
in chem-speak. Perfluorooctanoic acid (PFOA) is the adhesion promoter of choice. Unfortunately, it’s rather toxic, but according to the manufacturers it’s not present in the finished products. PTFE itself melts at 620°F / 327°C. Most stoves can get pans up above that temperature, which is why nonstick pans shouldn’t be used for searing or under the broiler. DuPont says nonstick pans coated with PTFE are fine up to 500°F / 260°C and that the material won’t begin to “significantly decompose” until 660°F / 349°C. Still, don’t try it: polymer fume fever isn’t fun.
I personally use nonstick frying pans as a default for day-to-day cooking because they’re easier to clean and well suited to the type of food I eat. My stainless steel frying pan gets used for those times when I am cooking “for real” (not to knock my morning scrambled eggs) and want to deglaze the pan to capture the fond. But you might cook different foods than I do, in which case your default pan might end up being stainless steel or cast iron.
I recommend that you have at least three frying pans on hand: one for searing items such as fish, a second for sautéing vegetables, and a third for those times when you want to reduce a sauce or sweat onions at a lower temperature. I prefer Vollrath’s Lincoln Wear-Ever Ceramiguard 10” frying pans (EZ4010): they’re cheap, they get the job done, and the silicone handles are oven-safe. If you’re lucky enough to have a larger stovetop with burners rated for higher BTUs, snag a 12” / 30 cm frying pan in lieu of a third 10” / 24 cm pan. And, if you’re often cooking for one, a smaller 8” / 20 cm frying pan is a useful size for quick dishes like scrambled eggs.
You don’t need to completely wash nonstick frying pans every time you use them, unless there’s particulate food left behind. Wipe the pan down with a paper towel, leaving a thin layer of oil behind.
I find it useful to have multiple frying pans so that I can cook different components of a dish separately. Onions (left pan), for example, are often “sweated” at a lower temperature, to keep them from caramelizing, while sausage (right pan) needs to be cooked hot enough to trigger the Maillard reactions that give seared meats an intensely rich flavor.
Saucepans.
A saucepan, roughly as wide as it is tall and with straight sides, holds two to three quarts of liquid and is used in cooking liquid foods such as sauces, small batches of soups, and hot drinks like hot chocolate. Look for a pan that has a thick base, as this will help dissipate the heat and avoid hot spots that could burn your food. Keep in mind that many of the liquids cooked in a saucepan tend to be things that can burn, so it’s worth spending a bit more to purchase a pan that conducts heat better. I picked up my favorite saucepan as an “odd lot” piece from a department store set. (Be sure to snag the lid as well!) You might prefer a
saucier
pan, one that has rounded corners that are easier to get into with a whisk or a spoon.
Stockpots.
A stockpot holds two or more gallons of liquid and is used in blanching vegetables, cooking pasta, and making soups. Since most applications for a stockpot involve a large amount of water, burning foods is not as much of a concern as it is with a saucepan — unless you can figure out how to burn water! The stockpot I use is one of the $20 cheap stainless steel commercial varieties. Make sure to pick up a lid as well, because commercial sellers tend to sell them separately.
Cast iron pans.
You should have a good cast iron pan in your pot and pan collection. Cast iron pans are heavy, and their larger mass allows for better retention of heat. Cast iron pans can also be heated to higher temperatures than nonstick and stainless steel pans, making them ideal for searing foods such as meat. They’re also handy for baking items such as cornbread or deep-dish pizza. Just remember to avoid cooking highly acidic items such as tomatoes in them, because the iron will react with acidic items.
As with frying pans, when washing cast iron, don’t use soap. Instead, rinse the pan and wipe the inside to dislodge any stuck-on food, and then place the pan back on the stove. If the food is really stuck, throw in a few tablespoons of course salt and a spoonful or two of vinegar or lemon juice, and “sand” it off with a paper towel. Once your pan is clean, wipe it down with a little heat-stable oil such as canola or sunflower oil (but not extra virgin olive oil) and place on a burner set for low heat for a minute or so to thoroughly dry it out. And never let it sit in water for hours on end, because the water will ruin the finish. If you
do
end up with rust spots, don’t fear. You can use a metal scrubbing brush to scrape away the rust, and then reseason the pan with a coating of oil.
What’s the deal with pans made of different metals or with various combinations sandwiched together? It has to do with the differences in thermal conductivity (how quickly heat energy moves through a material) and heat capacity (how much energy it takes to heat a material, which is the same as how much energy it’ll give off when cooling).
Let’s start with the thermal conductivity of common metals in pans, along with a few other materials for reference.
Pans made from materials with a lower thermal conductivity take longer to heat, because the thermal energy applied from the burner takes longer to transfer up and outward. In physics-speak, this is called
low thermal response time
. In cooking, pans with low thermal conductivity (cast iron, stainless steel) are “sluggish” in response to changes in heat. Pop them on the burner, and nothing seems to happen for a while. Likewise, if you get them too hot and pull them off the burner, food in them will continue to cook for a while.
Given two pans of identical diameter, one cast iron and one aluminum, the aluminum pan will conduct the heat throughout the pan faster. Here’s a picture of this, using thermal fax paper (hey, not all of us can afford a thermal imaging camera!). Since thermal fax paper turns dark where heated, dark = hot and white = cold.
Cast iron pan on a gas burner = slower heat transfer.
Aluminum iron pan on a gas burner = faster heat transfer.
If you’re keen to try this yourself, grab a roll of thermal fax paper, heat your pan on the burner for 30 to 60 seconds, turn off the heat, and then place a square sheet of paper on top of the pan and coat it with a few cups of cold rock/kosher salt to help press the paper against the surface of the pan.
Notice that the gas burner has a wide radius and the gas jets are directed outward. Result? The
center
of the pan actually ends up being colder. The cast iron pan shows this well because the heat does not conduct through the material as quickly as it does with the aluminum pan, leading to a cold spot.
Specific heat is important, too.
Specific heat
is the thermal energy (measured in
joules
) needed to change a unit mass of material by a unit of temperature, and it differs between materials. That is, it’ll take a different amount of energy to raise a
kilogram of cast iron 1°C versus a kilogram of aluminum, because of how the materials are structured at the atomic level. How do common metals in pans compare in terms of specific heat?
Cast iron has a lower specific heat than aluminum. It takes roughly twice as much energy (897 J/kg*K versus 450 J/kg*K) to heat the same amount of aluminum up to the same temperature, and because energy doesn’t just disappear (first law of thermodynamics), this means that a kilogram of aluminum will actually give off
more
heat than a kilogram of cast iron as it cools (e.g., when you drop that big steak onto the pan’s surface).
It’s not just the thermal conductivity or specific heat of the metal that matters, though; the mass of the pan is critical. I always sear my steak in my cast iron pan. It weighs 7.7 lbs / 3.5 kg, as opposed to 3.3 lbs / 1.5 kg in the case of my aluminum pan, so it has more heat energy to give off. When searing, pick a pan that has the highest value of
specific heat * mass
, so that once it’s hot, it won’t drop in temperature as much when you add the food.
There are a few other factors you should consider when picking a pan. Cast iron and aluminum react with acids, so pans made of those materials shouldn’t be used for simmering tomatoes or other acidic items. Nonstick pans shouldn’t be heated above 500°F / 260°C. And then there are cases where the pan isn’t the primary source of heat for cooking: when boiling or steaming, the water provides the heat transfer, so the material used in making the pan isn’t important. Likewise, if you’re using an ultra-high-BTU burner (like the 60,000-BTU burners used in wok cooking), the pan isn’t a heat sink so heat capacity isn’t important.
What’s the deal with
cladded
metals? You know, pans with copper or aluminum cores, encased in stainless steel or some other metal? (
Clad
= to encase with a covering.) These types of pans are a solution to two goals: avoiding hot spots by evening out heat quickly (by using aluminum or copper), and using a nonreactive surface (typically stainless steel, although nonstick coatings also work) so that the food doesn’t chemically react with the pan.
Finally, if you’re buying a pan and can’t decide between two otherwise identical choices, go for the one that has oven-safe handles. Avoid wood, and make sure the handles aren’t so big that they prevent popping the pan in the oven.