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10 Chemistry Cooking Tricks From an Award-Winning Teacher (and Foodie)

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Before diving into the kitchen this Thanksgiving, it’s helpful to have some basic chemistry knowledge up your sleeve. Ever wondered what the fastest way to defrost a turkey is? Or how to make the perfect, lump-free gravy every time? Yesterday, the American Chemical Society's Sally Mitchell—an award-winning high school chemistry teacher and Albert Einstein fellow at the Department of Energy’s Office of Science in Washington D.C.—hosted a Reddit AMA to share some kitchen chemistry tips ahead of Thanksgiving. Outside of her own classroom, Mitchell teaches other chemistry teachers how to incorporate food chemistry into their lessons. Here are her 10 best chemistry-smart cooking hacks to help you concoct a fantastic feast this holiday.

1. THE SECRET TO PERFECT STUFFING IS STALE BREAD.

When is comes to stuffing, texture is key. According to Mitchell the secret to stuffing that’s neither overly dry or overly soggy is to make sure you’re starting out with stale bread: “The secret to a good stuffing is to make sure the bread is dried before adding the butter and water. If you used a cubed baguette, you need to dry out the bread over night by leaving it out exposed to the air or dry it slowly by placing the cubes in a warm oven until they are dried out before mixing in the other ingredients.”

2. AVOID OVER-SALTING BY PAYING ATTENTION TO FOOD TEMPERATURE.

All it takes is one dash of salt too many to push a dish into inedible territory. When seasoning your dishes this Thanksgiving, Mitchell says to be mindful of the temperatures of the food you’re preparing: “If you were to take a food that is hot such as soup and salt it to taste and then cool it down, it would taste too salty. So cold enhances salty and hot reduces the sensation of saltiness. Keep that in mind when you salt food for others.”

For home cooks who have already salted their food past the point of no return, Mitchell says there’s not much that can be done. This is especially true when it comes to baked goods, but she still attempts to find the silver lining in your over-salted cookie dough: "Too much salt in your cookies is hard to overcome, taste-wiseyou should try to shape them into objects with cookie cutters and use them for your decorations since the additional salt will help deter bacterial growth."

3. THE FASTEST WAY TO DEFROST A TURKEY IS TO GIVE IT A COLD BATH.

It’s best to plan ahead as far as possible when it comes to Thanksgiving dinner. But if you find yourself on Wednesday night with a fully-frozen turkey on your hands, Mitchell has some advice on how to get it thawing as quickly as possible: “Give it a bath. I would read the label on the wrapping and follow it. If you need to speed this up, a cold-water bath with running water in it defrosts the fastest. Moving water will defrost faster than standing water."

And if you still haven’t gotten around to picking up your turkey for Thanksgiving, Mitchell’s primary piece of advice is to buy it fresh and avoid the defrosting process all together.

4. WANT THIN COOKIES? CHOOSE BUTTER. WANT AIRY ONES? GO FOR SHORTENING.

When experimenting with cookie recipes, Mitchell says that there is a noticeable difference in cookies that use shortening versus cookies that use butter as their source of fat: “You can make them thin and crisp, soft and puffy, or somewhere in between … Butter will tend to make cookies spread out and shortening makes them puff more.”

5. THE RIGHT AMOUNT OF BUTTERFAT IS THE KEY TO WHIPPING CREAM.

Not all creams are created equal. It may be tempting to substitute heavy cream with light cream and half-and-half when that’s all you have on hand, but there are chemical differences in these ingredients that can have an impact on your final product. According to Mitchell, “The difference between all the different types of creams is the percentage of butterfat. Half and half contains 10 to 18 percent butterfat, light coffee cream contains 18 to 30 percent butterfat, light whipping cream contains 30 to 36 percent butterfat, and heavy cream contains at least 36 percent butterfat. To whip cream, it must contain at least 30 percent butterfat. The more the butterfat, the faster the cream will whip and the firmer it will be. (If you over whip your cream, it turns into butter and butter milk).” But if you’re just looking for a cream to use in your green bean casserole this year, Mitchell says whatever you have in your fridge will do.

6. PUT FLOUR IN COLD WATER FOR LUMP-FREE GRAVY.

Nothing ruins a plate of food faster than drowning it in unsavory, lumpy gravy. After years of putting up with awful gravy from her mother, Mitchell was inspired to teach herself how to make it the right way: “My inspiration to becoming a good cook was my mother, because she made the ‘worst’ gravy each year. I learned how to work with flour and thickening agents because of her gravy mistakes, and now I make perfect gravy every time. I recommend the roux…but you can always use the correct flour (gravy flour, you can buy this at the grocery store under several brand names) and always shake the flour in COLD water before adding to the hot drippings.”

7. KNOWING THE CHEMISTRY OF CARAMELIZATION = DELICIOUS DESSERTS. 

Different recipes call for different baking temperatures. For those of you who've ever wondered how the level of heat in your oven impacts the final taste of your dish, Mitchell breaks down the delicious chemistry: “Let me focus on caramelization of sucrose (common table sugar). At 170 degrees Celsius (340 degrees Fahrenheit) the sucrose molecule will start to break apart. As the process proceeds, hundreds of new and different compounds form giving sour and bitter flavors, and browning occurs. The sweetness goes down while the darker and more bitter the food gets. This is why sometimes I bake my cookies at a lower temperature to prevent caramelization and sometimes I bake them at a higher temperature. It depends on the final flavor I am trying to create.”

8. REHEAT LEFTOVER TURKEY RIGHT TO KILL BACTERIA.

Deciding when to toss out your Thanksgiving leftovers can quickly become a game of chance. Just because your turkey has been cooked all the way through doesn’t mean it can’t still harbor harmful bacteria after sitting in your fridge for too long. "Remember to always heat up food to at least 55 to 60 degrees Celsius (140 degrees Fahrenheit) to make sure bacteria that can cause foodborne illness is eliminated,” says Mitchell. “They (food safety.gov) recommend eating leftovers within 4 days if stored properly.”

9. BAKING SODA PAIRS WITH ACIDIC INGREDIENTS, WHILE BAKING POWDER BOOSTS LIFT.

Anyone who’s tried substituting baking powder for baking soda in a recipe knows there is indeed a difference between the two. Mitchell explains the chemical significance of both components in your baked goods: “Baking soda is used when ingredients are acidic. When a carbonate (baking soda is sodium hydrogen carbonate) mixes with an acid (vinegar, lemon juice, chocolate, brown sugar are just some examples of acidic foods) a chemical reaction takes place and carbon dioxide is released. This along with steam generated in the baking process will help leaven your brownies. But for an added lift, baking powder is also added. Baking powder usually contains an acid salt that neutralizes the baking soda found in the baking powder mixture and more carbon dioxide bubbles are released.”

10. YOU CAN PASTEURIZE AN EGG IN ITS SHELL WITHOUT ACTUALLY COOKING IT. 

The egg is a magical ingredient. They lend themselves to many different applications and cooking methods, and as Mitchell explains, “raw” eggs can even be made safe to eat through a nifty chemistry trick: “When you cook an egg, at specific temperatures for a specific amount of time, wonderful things can happen. Eggs can be pasteurized in their shells without really cooking them. Now you can have raw eggs, safe to use in recipes for mayo or Caesar salad dressing, without the worry of foodborne illness.” She also illustrates how slow-cooking an egg sous vide–style can result in the perfect boiled egg: “Eggs contain different kinds of proteins and each has its own setting point temperature. By controlling the temperature, you can set the proteins gently and cook them all the way through without the harsh temperatures you cannot control from directly cooking on the stove top.”

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How Long to Steep Your Tea, According to Science
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The tea in your cabinet likely has vague instructions about how long to steep the leaves. Bigelow, for instance, suggests two to four minutes for black tea, and one to three minutes for green tea. According to Lipton, you should "try singing the National Anthem" while waiting for black tea leaves to infuse.

But while it's true that tea brewed for 30 seconds is technically just as drinkable as a forgotten mug of tea that's been steeping for 30 minutes, drinkable shouldn't be your goal. Taste and—depending on the tea you're drinking—antioxidant and caffeine levels all depend on the amount of time the leaves are in contact with the water. So how early is too early to pluck out a tea bag, and how long can you leave it in before passing the point of no return?

THE SCIENCE OF STEEPING

To achieve the perfect timing, you first need to understand the chemical process at work when you pour hot water over tea leaves. Black, green, white, and oolong tea all come from the leaves and buds of the same plant, Camellia sinensis. (Herbal teas aren't considered "true teas" because they don't come from C. sinensis.) The teas are processed differently: Green and white tea leaves are heated to dry them, limiting the amount of oxidation they get, while black and oolong tea leaves are exposed to oxygen before they're dried, creating the chemical reactions that give the tea its distinct color and flavor. Damaging the tea leaves—by macerating them, rolling them gently, or something in between—helps expose the chemicals inside their cells to varying levels of oxygen.

Both green and black teas contain a lot of the same chemical compounds that contribute to their flavor profiles and nutritional content. When the leaves are submerged in hot water, these compounds leach into the liquid through a process called osmotic diffusion, which occurs when there's fluid on both sides of a selectively permeable membrane—in this case, the tea leaf. Compounds on the surface of the leaf and in the interior cells damaged by processing will diffuse into the surrounding liquid until the compounds in both the leaf and the water reach equilibrium. In other words, if given enough time to steep, the liquid in your mug will become just as concentrated with tea compounds as the liquid in your tea leaves, and the ratio will stay that way.

Osmotic diffusion doesn't happen all at once—different compounds enter the water at different rates based on their molecular weight. The light, volatile chemicals that contribute to tea's aroma and flavor profile dissolve the fastest, which is why the smell from a bag of tea leaves becomes more potent the moment you dunk it in water. The next group of compounds to infuse with the water includes the micronutrients flavanols and polyphenols, which are antioxidants, and caffeine. They're followed by heavier flavanols and polyphenols such as tannins, which are the compounds responsible for tea's bitter flavor. (They're also what make your mouth feel dry after drinking a glass of wine.) Tea also has amino acids like theanine, which can offset the sharpness of tannins.

Water temperature is another factor to take into consideration when steeping your tea. High water temperature creates more kinetic energy, which encourages the compounds to dissolve. "The heat helps you to extract the compounds out of the tea leaves," Shengmin Sang, a North Carolina A&T State University researcher who studies the chemistry of tea, tells Mental Floss. "If you put it into cold water or low-temperature water, the efficiency to extract these compounds out of the leaves will be much lower." But not all water is equal: Bigelow Tea recommends using water at a rolling boil for black tea, and barely boiling water for green tea.

LOOSE LEAF VS. TEA BAGS

Osmotic diffusion takes place whether you use loose leaves or tea bags, but there are some notable differences between the two. When given room to expand, loose tea leaves swell to their full capacity, creating more room for water to flow in and extract all those desirable compounds. Tea that comes prepackaged in a bag, on the other hand, only has so much room to grow, and the quality suffers as a result. This is why some tea companies have started selling tea in roomier, pyramid-shaped bags, though the size matters more than the shape.

But even before the tea touches the water, there's a difference in quality. Loose leaf tea usually consists of whole leaves, while most teabags are filled with broken pieces of tea leaves called dust or fannings, which have less-nuanced flavors and infuse fewer antioxidants than whole leaves, no matter how long you let them steep.

So if you have a choice, go with loose leaf. But if tea bags are all you have on hand, don't bother adjusting your brewing method: The difference in taste and antioxidants isn't something that can be fixed with a few extra minutes, and according to Sang, you should follow the same steeping times for both tea bags and loose leaf.

To calculate the perfect brew times for what's in your mug, first consider what you want most out of your drink.

IF YOU DRINK TEA TO BE HEALTHY

Suggested steeping time: 2 minutes, 30 seconds to 5 minutes

Tea leaves are packed with beneficial compounds. Research indicates that flavanols such as catechins and epicatechins, found in both green and black teas, help suppress inflammation and curb plaque build-up in arteries. Drinking tea may improve vascular reactivity, which dictates how well blood vessels adjust to stress. According an analysis of multiple tea-related studies published in the European Journal of Epidemiology in 2015, drinking three cups of tea a day reduces your risk of coronary heart disease by 27 percent, cardiac death by 26 percent, and total mortality by 24 percent. Polyphenolic antioxidants in tea may also protect against diabetes, depression, and liver disease.

Past research has shown that it takes 100 to 150 seconds to extract half the polyphenol content from green and black tea leaves. According to a study published in 2016 in the journal Beverages, you can get more polyphenols into your drink if you allow the leaves more time to steep. However, the returns may not be worth the extra effort: Most of the compounds the researchers measured after 10 minutes of steeping were extracted in the first 5 minutes.

Sang makes another argument for not waiting too long to drink your tea. Antioxidants are slightly unstable, which means they will eventually break down and lose their healthy properties after infusing with water. “After you extract the compounds from the tea bag, you can not keep the solution for too long,” he says. “Because these compounds are not stable, they will be oxidized. So if you brew it in the morning, then you drink it in the afternoon, that's not good.” This oxidation can occur even after the tea leaves are removed from the cup, so if your tea has been sitting out for a few hours, it's better to brew a new batch than to pop it in the microwave.

IF YOU DRINK TEA FOR THE CAFFEINE BOOST

Suggested steeping time: 3 to 5 minutes

Though less potent than its rival coffee, a properly brewed cup of tea packs a caffeine punch. According to a 2008 study published in the Journal of Analytical Toxicology [PDF], letting your tea brew for at least a few minutes has a big impact on the caffeine content. The study found that after brewing for one minute, a cup of regular Lipton black tea had 17 milligrams of caffeine per 6 ounces of water, 38 milligrams per 6 ounces after three minutes, and 47 milligrams per 6 ounces after five. (The nutritional information for Lipton black tea says a serving contains 55 milligrams of caffeine per 8 ounces, so it's pretty accurate.)

Some people may use those numbers as an excuse to steep their tea past the five-minute mark in an attempt to reach 100 percent dissolution. But a longer brewing time doesn't necessarily equal a stronger caffeine kick. Yes, more caffeine molecules will enter the tea, but so will other compounds like thearubigins. Caffeine works because it's perfectly shaped to bind to certain neuroreceptors in your brain, thus blocking the chemicals that tell you to feel tired. But caffeine is the right shape to bind to thearubigins as well, and if that happens first, less caffeine will get to those neuroreceptors. So if you're looking for a highly caffeinated cup of tea, you should remove the leaves after most of the caffeine has been extracted—after about three to five minutes—rather than waiting for every last milligram of caffeine to dissolve.

IF YOU DRINK TEA BECAUSE IT TASTES GOOD

Suggested steeping time: 1 to 3 minutes

There's nothing wrong with enjoying a cup of tea for taste alone. Flavor is the most subjective factor influenced by steeping times, but for the sake of simplicity, let's assume you prefer a pronounced tea taste that's not overshadowed by bitterness. To extract those more delicate flavors, you don't need to steep your tea leaves for very long at all. Some of the first volatile organic compounds to break down in tea are geraniol and phenylacetaldehyde, tied to a tea's floral aroma, and linalool and linalool oxide, which give tea its sweetness.

The other compounds we associate with tea's distinctive taste are tannins. They're the difference between an aromatic, fruity cup of tea and a bitter cup that needs to be diluted with milk before it's palatable. But tannins aren't all bad: Some people prefer their tea to have a bracing astringency. Because tannins are some of the last molecules to dissolve into tea, if you want to add some bitter complexity to your drink, steep your tea for a minute or two longer than you normally would. A good way to keep track of the strength of your tea is to look at the color: Like tannins, pigments are heavy compounds, so if you see your tea getting darker, that means it's getting stronger as well.

And what about herbal teas? Feel free to leave the leaves in as long as you like. Because herbal teas are high in aromatic compounds and low in tannins, drinkers can be more liberal with their steep times without worrying about getting that astringent taste. Some teas, like rooibos and chamomile, also contain antioxidants, which is another reason to take your time.

And if you're new to the world of tea and aren't sure what your preferences are, put a kettle on the stove and start experimenting.

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Hawaii's Kilauea Volcano Is Causing Another Explosive Problem: Laze
Mario Tama, Getty Images
Mario Tama, Getty Images

Rivers of molten rock aren't the only thing residents near Hawaii's Kilauea volcano have to worry about. Lava from recent volcanic activity has reached the Pacific Ocean and is generating toxic, glass-laced "laze," according to Honolulu-based KITV. Just what is this dangerous substance?

Molten lava has a temperature of about 2000°F, while the surrounding seawater in Hawaii is closer to 80°F. When this super-hot lava hits the colder ocean, the heat makes the water boil, creating powerful explosions of steam, scalding hot water, and projectile rock fragments known as tephra. These plumes are called lava haze, or laze.

Though it looks like regular steam, laze is much more dangerous. When the water and lava combine, and hot lava vaporizes seawater, a series of reactions causes the formation of toxic gas. Chloride from the sea salt mixes with hydrogen in the steam to create a dense, corrosive mixture of hydrochloric acid. The vapor forms clouds that then turn into acid rain.

Laze blows out of the ocean near a lava flow
USGS

That’s not the only danger. The lava cools down rapidly, forming volcanic glass—tiny shards of which explode into the air along with the gases.

Even the slightest encounter with a wisp of laze can be problematic. The hot, acidic mixture can irritate the skin, eyes, and respiratory system. It's particularly hazardous to those with breathing problems, like people with asthma.

In 2000, two people died in Hawaii Volcanoes National Park from inhaling laze coming from an active lava flow.

The problem spreads far beyond where the lava itself is flowing, pushing the problem downwind. Due to the amount of lava flowing into the ocean and the strength of the winds, laze currently being generated by the Kilauea eruptions could spread up to 15 miles away, a USGS geologist told Reuters.

[h/t Forbes]

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