Cooking for Geeks: Real Science, Great Hacks, and Good Food

by Jeff Potter

  What’s the rationale prohibiting carbon knives in restaurants?

  They rust, and rust is iron oxide. It’s dirty, and where the blade has rusted, there are pits that will retain grease. The grease will breed bacteria. It’s usually controlled by city or state or county ordinance.

  Carbon steel versus stainless steel. Which is better?

  That was a classic question that I wondered about for 30 years. I finally had a seminar with a metallurgist from a French steel mill, and he developed a machine to test the sharpness of edges and the life of edges. The answer is that you can get a carbon steel edge about 5% sharper while a stainless steel edge will last about 5% longer. With stainless steel being tougher, it is harder to create the edge, so stainless steel often gets a bad reputation because people can’t sharpen it correctly. It is possible to get carbon steel 5% sharper, but you would never perceive that using a knife. You need the scientific apparatus to bring out that difference. The practical difference is it’s very easy to bring up an edge on carbon steel, so most people’s carbon steel knives are sharper because they’re easier to resharpen. A carbon steel knife responds very easily to a butcher’s steel; you have to work a little bit more with a stainless steel knife.

  I’m going to ask the question that’ll probably lead to the gates of Hell: how do I sharpen a knife correctly?

  There are lots of ways to do it. Probably the best general-purpose way and what I recommend to people is to use a diamond sharpening steel. The traditional serrated butcher’s steel is a ½″ or ⅝″ rod with ridges running longitudinally. Those are now being replaced by rods that are plated with diamond. The diamond rod brings up an edge very quickly, because it’s hard enough to remove metal, creating a new edge.

  An edge is actually a whole bunch of little burrs, sort of like hacksaw teeth that are standing up, perpendicular to the back of the blade. When you cut, those little burrs (here we call them feathers) roll over. The first thing that happens when you swipe with a butcher’s steel is you stand those feathers up, and you have a real good edge. After a time, they bend back and forth. They work-harden and break off, like breaking a wire by twisting it until it work-hardens and snaps. Then you have to create a new edge, new burrs, and the grit on a diamond steel is perfect for that. That’s what the long serrations do on your regular butcher’s steel, but it’s a lot easier to do with a diamond steel.

  When you run a knife edge along a steel, you stand up the burrs, and you start thinning down the edge. I can do it with the back of a porcelain plate, or I can rub a knife on a brick wall and bring up the edge, but a diamond steel is best.

  I’ve made a lot of trips to China, and they have very primitive kitchens as far as equipment, tools, and utensils go. They make do with the one basic knife. People call it a cleaver, but it’s not really a cleaver. It’s a slicer and a spatula and a scraper and everything else, but with that one knife, they stop and squat on the floor and bring the edge back on a brick that’s in the floor. They keep those knives very, very sharp. I learned in Chinese cooking how nicely things are sliced up counts as much as the taste, the presentation, and the freshness of ingredients. All of that can be ruined if you have cut raggedy chunks.

  I would recommend either a diamond butcher steel or a whet stone. But a whet stone takes more skill, more training to use. I would stay away from electric sharpeners.

  At some point the burrs snap off, and I presume that’s the point at which one needs to actually grind down the edge of the knife to form a new edge?

  With a diamond steel, you’re doing grinding at the same time you’re straightening up the edge. A traditional butcher’s steel isn’t hard enough to remove metal. The deal with using a butcher’s steel is your steel has to be harder than the metal of the blade you’re sharpening. Otherwise, you get nowhere, like using a common file to smooth or shape metal. Your file won’t cut the metal if the file isn’t harder than the metal it’s cutting. If you let your knife get very dull, bringing the edge back is a real bear. If you give it a few strokes on a butcher’s steel every other day, or once a week, or every time you go to put the knife in the drawer, then the knife is always ready.

  At what point is a knife effectively used up? [Buck shares with me the photo shown below.] I cannot believe how much the bottom knife has been sharpened away compared to the new knife on top. What’s the story with this actual knife?

  Whoever was resharpening that knife was very, very good. It came back to our customer service people for replacement from a mom-and-pop butcher shop. I train our sales force, and one of the questions they ask is how long is a knife useful. I show them this. That’s pushing the ridiculous. I would think that that knife had seen about five or six years of service.

  We usually find in a restaurant that a knife is good for six to nine months. With professional cutlery, and in particular with packing houses, they’ll need a wide blade for breaking down a side of beef. They need a large curved knife, which we call a cimeter steak knife. When it starts out life, it’s about 2 1/2″ wide, and when it gets down to about 1″ or 1 1/4″ wide, it’s no longer suitable for breaking down the big sides of beef. So then they use it for the smaller cuts, and call it a breaking knife. When they wear it down to about under an inch, they use it as a boning knife.

  So these knives actually go to a series of different lives? As they get smaller from sharpening, they get repurposed and reused?

  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.

  Knife Sharpening 101

  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 in
volves 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.

  Cutting boards

  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.

  Note

  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.

  Pots and pans

  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.

  Note

  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.

  Note

  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.