The STEM in Kitchen Appliances

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We just returned from a visit to Le Cordon Bleu School in Cambridge, Massachusetts, where our older son is considering getting a culinary arts certificate after his high school graduation in (gasp!) June. We took a tour of their many kitchens, and I was impressed by the size of the mixers in the baking kitchen. Upon return, our microwave mysteriously quit working and my husband and I had a conversation about how appliances just aren’t built like they used to be. Happily, I discovered after some investigating that the unit had become unplugged from the socket in the back of the cabinet under which it is mounted. One problem solved!

All this recent exposure to the workings of kitchen appliances did make me think that there was a column in there somewhere. Modern kitchen appliances are powerful while being resource efficient, but all kitchen appliances have long histories. Many began with simple machines. The industrial-size stand mixers that they have at Le Cordon Bleu, for instance, are based on levers and wheels. (Gears are wheels with teeth.)

Power, efficiency, and energy

Early kitchen appliances were much more identifiable with their simple machine roots. My personal favorite kitchen tool is still the manual egg beater. This device, patented in 1894, was intended by its inventor to be a mixing machine for many different applications, not just eggs. The double sided drive wheel is powered by the motion of the handle and smaller gears transmit the power to the two beaters. One of the earliest kitchen appliances was the roasting jack, which was a mechanism based on the wheel for turning meat on a spit. Spits were originally turned by hand and are thought to date back thousands of years. The manual butter churn was based on a lever or a wheel. Each of these once-common kitchen fixtures has since been supplanted by a more efficient machine. When I was a child, our next-door neighbor had an old washing machine in which the agitator was powered by electricity but once the clothes were clean and rinsed the water was squeezed out by hand-cranked wringers. This method seems labor intensive by today’s standards but was a huge improvement over a tub and washboard.

The potential of electrical kitchen appliances to reduce labor was seen as early as 1917, as published in the National Electric Light Association Bulletin. At that time the author was mainly concerned with how the refrigerator would free up the ice man for military service, but other implications were becoming known as well. Labor-saving kitchen devices freed up significant amounts of time for women, allowing them the freedom to work outside the home. Early electrical kitchen appliances may have started a social revolution as early as the 1920s. Widespread adoption of electrical kitchen appliances had an undoubted influence on the women’s liberation movement

Today’s kitchen appliances save more than just labor. Modern dishwashers are designed to be energy efficient while using significantly less water than hand washing. Most new dishwashers use less than 5 gallons of water per load. This saves energy in a couple of ways, because in addition to using less electricity to power the machine, less energy is required to heat the water.

Physics and technology

Microwave ovens make an interesting physics lesson. You may have heard the story of how microwaves were discovered by accident, when Percy Spencer, an engineer was working with the high-powered vacuum tubes that produced radio waves used in radar. He noticed that a peanut cluster candy bar in his pocket began to melt. This led Spencer to discover the existence of microwaves, which have shorter wavelengths than radio waves. Both radio waves and microwaves are forms of electromagnetic energy. These kinds of energy both have significantly longer wavelengths than the electromagnetic energy you’re most familiar with, which is light. Microwave ovens are set to emit energy at a specific wavelength, which excites water molecules in food, so that the molecules vibrate and produce heat. This heat is what cooks or reheats the food. The metal walls of the oven reflect the microwaves, ensuring that no waves escape to cause harm to hungry people.

A new technology that is making its way into kitchens is induction cooking, in which heat is generated by strong electric fields. These kinds of stovetops are safer and more efficient than their conventional ancestors. The catch to induction cooking, though, is that you can only use pans made of ferromagnetic metals on them. Other types of pan will not heat up because their electrons cannot be excited. In a lovely example of old meeting new, the precise temperature control afforded by these appliances allows even novice cooks to follow some of the recipes in Julia Child’s iconic Mastering the Art of French Cooking with something like confidence. (Words to the wise—if you attempt to use one of those recipes, read it all the way through before you begin. Maybe twice. Julia Child was precise.)

Connected kitchens

The Internet of Things is beginning to make inroads in the kitchen, as well. Options for “smart” appliances that are wi-fi enabled and controllable by an app include refrigerators, stoves. dishwashers and crockpots. (Our crockpot, in which tonight’s dinner has been cooking as I write, is not so fortunate.) I am looking forward to the day when I can put ingredients in the crockpot or oven the night before, knowing they will stay refrigerated until the appointed time, and then will be cooked to perfection by the time everyone at arrives home. All of this will be arranged with a few touches on a smartphone screen. This day may not be as far off as you think—there is already a marketed oven that refrigerates food until it is time to cook.

Produced by the National Science Teachers Association (NSTA), science writer Becky Stewart contributes monthly to the Science and STEM Classroom e-newsletter, a forum for ideas and resources that middle and high school teachers need to support science, technology, engineering, and math curricula. If you enjoy these blog posts, follow Becky Stewart on Twitter (@ramenbecky).

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