The Science and Engineering of Happy Cooking

A little microbiology, and no psychology

When Warren Buffet was asked what the secret to a happy marriage is, he said “low expectation”. Note that we are not talking about the secret to be good, because there is no secret to good cooking: It’s hard work, connections, and luck. It not only takes years of study and practice but also what Bjarne Stroustrup said a good C++ programmer should possess: good taste.

Fortunately you don’t have to be good to be happy. There are many good reasons to cook even if you have no intention of becoming a professional chef. Cooking at home helps you eat healthy. It saves money. It’s a good exercise. It brings family and friends together, etc. They are all true. I will just mention two reasons that are the most compelling to me:

1. If you are serious about sticking to a diet plan, cooking your own meal is the best way to do it (Or get a chef to do it for you. If you look carefully, you will see in the end credits of Avengers: Endgame a personal chef for Robert Downey Jr.).
2. How often does a corporate man get the chance to have complete artistic, technical, and operational control over a non-trivial project? The president probably never gets to do it. Tim Cook probably can do it once every two years.

The prerequisite for happy cooking: safety

A Canadian friend of mine once joked that the hockey rink is a perfect place to have a fight: you already have knives and sticks. The kitchen is a perfect place to have an accident: Fire, sharp tools, high voltages, and countless pathogens are present in the kitchen. The first secrete to happy cooking is: be safe.

There are two aspects to safety in the kitchen: physical safety for the cook and food safety. Being organized is the starting point for both types of safety. Instead of giving you advice on how to be organized (you can find plenty elsewhere), I offer two observations when you know you are not organized:

1. You turn more than 180 degrees when you look for something.
2. You find yourself opening the fridge door or the spice drawer with greasy hands all the time.

And a couple of counterintuitive observations that you are organized:

1. You are running out of bowls/saucers.
2. You seem to have a lot of space in your pantry.

Food Safety

Food pathogens are biological agents in food that make you sick, either directly or indirectly (through the toxin they release). Common food pathogens include parasites, bacteria, and viruses.

The first line of defense against food pathogens is to buy from reliable sources. Some pathogens can not be eliminated at home. For instance, if the beef is already contaminated, cooking steak well done will not reduce the risk of mad cow disease. I am not one to vouch for bureaucracy. But like it or not, meat production and distribution are heavily regulated in the United States. For instance, USDA requires an inspector present for any slaughterhouse to operate. If you buy from the normal regulated channels, meat should be safe to eat. For example, it’s now extremely rare to find parasites in meat. But as Reagan said, the 9 most terrifying words in the English language are “I am from the government and I am here to help”. Just google “Creekstone farms BSE rapid testing”.

The second line of defense is to wash your hands. They touch everywhere in the kitchen, and outside the kitchen. Surgeons wash their hands carefully before they enter the operations room, and so do professional chefs before they start prepping. Here are some tips for washing your hands:

1. Wash long enough. It takes time for the soap to do its job. Apple watch now has a feature that automatically tracks how long you wash your hands. Turn it on.
2. A lot of people remember washing between fingers but overlook washing their thumbs thoroughly.
3. It’s best to get a brush to wash under your fingernails.

This story in Modernist Cuisine shows how hard it is to wash hands well: navy doctors swabbed some UV powder around the rectums of sailors without telling them. The next day traces of UV powder were found all over the ship under UV light.

Keeping your hands clean is an essential part of the third line of defense: minimizing cross-contamination. It’s a common misconception that raw meat is the only source of food-borne pathogens. Vegetables deserve the same level of scrutiny. What defense does a spinach field has against a sick wild boar defecating in it? That was exactly how the 2006 E Coli outbreak got started. Incidentally, an important benefit of being organized is reduced risks of cross-contamination.

Side towels are a great convenience, but they can also be a medium for cross-contamination. Be mindful of what is on your hands when you wipe them. I keep a small bottle of bleach in my kitchen and regularly disinfect my side towel with diluted bleach.

In reality, unless you treat your food like biohazard waste, it’s very hard to completely eliminate cross-contamination. This brings us to our last line of dense: cooking with heat.

A common food-borne pathogen is bacteria. Most bacteria rely on binary fission (splitting in two) for propagation. Therefore, the number of bacteria grows exponentially. However, it takes time for a bacteria cell to mature enough to split. Researchers in the field of predictive microbiology are working hard to understand how different environmental factors, including temperature, pH value, water activity, and the existence of other organisms, affect the timing of microbial reproduction.

The thermal death time curve of bacteria has been well understood for some time. All else being equal, the life and death of bacteria are regulated by temperature. At a really low temperature (under freezing), bacteria either die or stop reproducing. Above around 5⁰C, as temperature rises, the bacteria reproduction rate also increases. They grow the fastest at around 40⁰C. After that the growth rate decreases. Above 55⁰C bacterial start dying. The temperature range between 5⁰C and 55⁰C is considered the danger zone for food safety.

A common misconception is that bacteria are killed, and only killed under high temperatures. Remember temperature is the average measure of a random process. When a bacterial cell will die under a certain temperature is also an exercise in probability. When bacteria start dying, if the temperature rises, more bacteria die in a given time; if the temperature is held steady, more bacteria die as time passes.

Figure 1: Thermal death curve

As shown in Figure 1, there are two ways to get to the same reduction of bacterial population: higher temperature, shorter time or lower temperature, longer time. In other words, just because your food has reached a “safe” temperature, it doesn’t mean it’s safe to eat right away.

In food sanitation, the reduction in bacteria is often indicated with the D number. 1D means a reduction by a factor of 10. 2D reduction means only 1/100 is left. According to data published by Vijay Juneja, a research scientist at USDA, these are the temperature and time to achieve 6.5D reduction in Salmonella for chicken breast meat:

2 minutes 36seconds at 63⁰C

20 minutes 56 seconds at 60⁰C

29 minutes 32 seconds at 58⁰C

1 hour 15 minutes at 55⁰C

The good news here is you don’t need to overcook chicken to render it safe to eat. For my taste chicken breast cooked to 63⁰C is too dry. I would rather cook it for 30 minutes at 58⁰C.

Bacteria mostly live on the surface of the meat. The inside of the meat should be clean. However, if you puncture the meat, say, with a meat thermometer, you run the danger of contaminating the inside with bacteria on the surface. If you want to monitor the internal temperature of a piece of steak, you should do it after you have seared the surface of the steak. That’s also why you should crack eggs on a flat surface instead of on the edge of a bowl so that you don’t let shell fragments contaminate the inside of the egg. Burgers made with ground beef should always be cooked to a higher temperature than a piece of intact steak.

Lastly a disclaimer: I am not a microbiologist. I offer no guarantee about the correctness of the information presented here. I can not be responsible for anything that might happen if you follow the advice here.

Physical Safety

In general, you should be safe if you are organized and move calmly and with purpose. One fear of new cooks is cutting themselves. You can find many videos online that show the proper techniques for handling knives. At a high level, using knives safely is not that different from driving safely:

1. Go slow. There is no award for being fast.
2. Focus and watch where you are going. 90% of the time an accident with knives happens because you are not paying attention to the knife when you cut.

The other 10% of accident happens because the knife is not sharp enough. It’s counterinutitive to new cooks that a sharper knife is safer. Think about it this way: if you hand is not in the potential path of the knife’s movement, you can not cut yoursself. When you have a dull knife and you have to force it, you increase the danger of losing control of where the knife is going. You don’t need fancy tools to sharpen a knife, a 1000 grit whetstone is all you need. At first, it might seem like you can’t get it right no matter what you do, but be patient and practice. It’s like the golf swing. Not everyone can become Tiger, but anyone can develop a natural, comfortable swing if they stick to it and pay attention. Here are some tips to help you practice:

1. To find the right angle to sharpen, you don’t need a protractor or tricks like stacking 2 coins. Every model of knife is different. A universal angle doesn’t exist. Just lay the knife flat on the whetstone, and slowly lift the spine. You can feel the grind line. Follow the angle of the existing bevel to grind. See figure 2 for illustration. Some Japanese knives have a concave side. I wouldn’t try to sharpen those myself.
2. The direction of sharpening is the direction where you don’t cut into the whetstone, as in figure 3
3. As you sharpen the blade, a curved lip on the side will form as in figure 4. That’s a sign you are doing it right. You can safely feel the burr with your finger. It should be obvious.

Figure 2: Finding the grind line

Figure 3: Direction of sharpening

Figure 4: The burr

As in every other aspect of cooking, safety requires attention to detail. Here are two examples to help you start paying attention:

1. As you put a sharp knife down between cutting, make sure the blade faces outward, if your hands will continue to work inside the area of the cutting board.
2. Accidentally knocking things over in the kitchen is not only annoying but also dangerous. Watch where the handle of your pan is. Make sure it’s not in the path of your movement.

Figure 5: Safe pan handle position

There is an old Chinese saying: “A virtuous man does not stand near a collapsing wall” （君子不立危墙之下）. True professionals take precautions and eliminate risks.

Equipment

We are not going to talk about pots and pans and knife sets. Every cuisine style has its own unique set of essential tools. A French chef does not use a wok. A Chinese chef does not use a Dutch Oven. Sushi chefs not only use special knifes, but also special cutting boards. It’s almost certain you will end up with tools you rarely use whatever list of “essential kitchen tools” you follow.

However, two essential pieces of equipment that are universally useful are rarely mentioned in those lists: the thermometer and the scale.

A large part of cooking is temperature control. No measurement, no control. There are four different types of thermometer for home use: the mechanical thermometer, the mercury thermometer, the digital thermistors, and the infrared thermometer. The mechanical thermometer with an analog dial has the least accuracy. I don’t recommend it unless you want a couple of cheap oven thermometers, where the accuracy requirement is not that high anyway. The mercury thermometer is more accurate, but a little inconvenient to use. I recommend every cook have at least one digital thermistor and one infrared thermometer. The infrared thermometer is extremely useful when you can not or do not want to touch the ingredient, like when tempering chocolate.

A scale is an important tool for following recipes and diet plans. It’s critical to measure carefully for baking and, depending on who you ask, espresso. I recommend you get two scales. One is the normal kitchen scale that can weigh up to 1 kilogram. Unfortunately, most of these scales for home use don’t have enough accuracy to measure 1 gram increment. I won’t rely on them if you need to measure 2 grams of yeast. You should also get what is known as a jewelry scale. A cheap one can measure down to 0.1 gram. The drawback is they don’t have a lot of range.

A piece of important information you should get with the jewelry scale is how much a pinch of salt weighs. It’s much more convenient to have a rough idea than to measure the salt out every time. For me, a two-finger pinch weighs between 0.2 grams to 0.4 grams. A three-finger pinch weighs between 0.7 grams to 1 gram. And a four-finger pinch weighs between 1.5 grams to 1.8 grams. The results are surprisingly consistent.

Now that you have a simple way to know the amount of salt you put in the dish, how much should you add? My experience is different people have vastly different levels of sensitivity to salt. The salt concentration in human saliva is about 0.5%. In theory, if the salt concentration level is 0.5% in the food, you should not be able to taste it. If it’s less, the food will taste off. So that’s the level I will start with.

Techniques

You will not become a good cook by reading about techniques:-) A home cook can find many great recipes, cooking classes, and demonstration videos online. But I do have a few lessons learned to share:

1. Try not to cook hungry. Timing is important in cooking. If you rush things, you will not get it right.
2. When you watch a cooking video, don’t just look at the ingredient list and the end result. Pay attention to what it looks like at every intermediate step.
3. If you are going to follow a recipe, follow the recipe. At least once. Every recipe tries to achieve a certain flavor. If you don’t follow it, you will never know what it really tastes like. Don’t skip the bay leaf, or replace the Nicoise olives with Kalamata olives. And don’t change the portions. There is such a thing as too many sausages in the Gumbo!
4. Be patient. If it’s the first time you make a dish, budget twice the time you think you need. You will get faster with practice.
5. A few tricks that almost always improve any home-cooked dish: 1)more salt. 2)more butter. 3)smaller portion size. 4)Cook all ingredients separately and mix them together at the end.

My expectation for my own cooking is to cook decent food that helps me stick to a healthy diet, bring family and friends together, and have fun. Leave the making of spectacular food to 3 Michelin star restaurants. Those 400 dollar dinners are a very good deal, seriously.

How not to lie to yourself

Any cook who strives to make continuous improvements will want to find ways to get objective feedback on their experiments. An A/B blind test is not informative because when people are looking for differences, they make up all kinds of sensations in their minds. The right way to do it is to set up a triangle taste test.

In the triangle test, you give the tester 3 blind samples of food at the same time. One is different than the other two. If possible, all three samples should look the same. If you have more than one taster, the order the samples are presented should be randomized. The first step is for the taster to find which sample is different than the other two. The second step is to identify which one the taster prefers. Obviously, if the taster can not pick out the correct odd sample in the first step, the result of the second step doesn't mean anything.

Try it. This kind of test not only gives you feedback on the food but also teaches you about your tasting capabilities.

Ideas for a better kitchen scale

I have two main uses for the kitchen scale: 1) weigh food to track my progress in following the diet, 2) weigh ingredients to follow a recipe (the simplest of which is the morning coffee: bean and water). In both cases, the user’s goals can not be accomplished by a single measurement. It needs the accumulation of a series of measurements.

To support that, the scale needs to be able to do at least three things:

1. It should be capable of being informed of the intended measurements.
2. It should know what is being measured. It prompts the user for the next measurement to be made. Because it knows the whole sequence, it’s not fazed when the user changes the order, will notify the user when all measurements are done, and remind the user when they forget to weigh something.
3. It should automatically record all the data and present them to the user.

No. I am not advocating putting a screen on the kitchen scale. We have too many screens in our homes already. As long as the scale can connect to the house wifi, It should be controllable from an App.

But this setup has two problems in my opinion: a simple one and a difficult one. The simple one is that I shouldn’t have to reach for my smartphone if I just want to weigh something. The scale should still support all the basic functionality users expect from an old fashion kitchen scale on its own.

The difficult problem is this: a lot of diets fail not because people don’ want to weigh their food, but because the record-keeping becomes too much. In my opinion, the one feature that really adds value to the scale is keeping a record without my doing anything.

Now I don’t think the kitchen scale should be equipped with computing power that can potentially mine Ethereum. The captured images should be wirelessly sent to the app for processing.

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