Whether you’re a seasoned chef or a stovetop newbie, it’s always fun to try out new techniques in the kitchen—especially if those techniques can save you some time and money. Over the last few years, we’ve seen an influx of so-called “kitchen hacks,” which repurpose common household materials to help with cleaning, cooking, and everything in between.

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Unfortunately, some of those kitchen hacks don’t really work. To separate the true timesavers from the…uh, timewasters, we decided to look into the science. Below are kitchen hacks that didn’t come from, well, hacks.

1. Hate brown apples? Lemon juice is here to save the day.

As far as the internet is concerned, lemon juice is basically a scientific miracle elixir. It’s great for cleaning, ideal for cooking, and an ideal eyewash (we’re joking about that last one—don’t try it).

In this case, the science supports most of those uses. One of the cooler examples we found: Lemon juice can actually help to preserve certain foods.

The next time you’re slicing up some fruit for a snack or dessert plate, put a few drops of lemon juice and water on your apple slices to stop them from browning prematurely. This also works for avocados (keep that in mind the next time you’re making guacamole) and pears.

Why do some fruit change colors, anyway? It’s a pretty simple chemical reaction. Nationally recognized educator and chemist Sally Mitchell explains that, really, oxygen is to blame. Sure, we need to breathe the stuff to stay alive, but that doesn’t mean it’s all good.

“The browning of fruit is caused is considered an enzymatic browning,” Mitchell tells Urbo. “The fruit contains the phenolic compounds inside of storage vacuoles while the enzymes are floating in the cytoplasm of the cell. If the cell structure is damaged, then the phenolic compounds will react with the enzyme and oxygen and browning will occur.”

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We’ll try to simplify that explanation: When you cut into a fruit, you’re cutting through a bunch of cell walls, releasing compounds that react with enzymes and oxygen to cause browning. Onions make us cry for a similar reason (more on that in a moment).

The good news is that when you change the pH around an enzyme (with something acidic like lemon juice), you stop this reaction and prevent browning.

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Now, lemon juice isn’t your only option for keeping food fresh. Pretty much any juice with citric acid will prevent the enzymatic reaction, but keep in mind that whatever juice you use will also flavor your food. If you’re worried about the flavor profile, go for citric acid crystals or even a crushed-up vitamin C pill, which should work as well as fruit juice.

2. To keep your gravy nice and gooey, grab some powdery stuff.

If you find yourself stuck with a runny bechamel or mushroom gravy, there’s a fix.

Making a sauce from scratch can be tricky, thanks to the First Law of Saucitivity, which we just made up: Consistency is everything. Don’t worry if you can’t seem to get the balance down right away—it’s not that hard to kitchen hack your way to saucey greatness.

Flour and cornstarch are two main options for thickening a sauce. While both will work in almost any cooking situation, know the differences before you reach into the pantry. Your thickening agent will vary depending on your cooking process, timeframe, and the ideal consistency of the dish.

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That’s because flour is mostly made up of starch and protein, whereas cornstarch is 100 percent starch, Mitchell says.

“You need more flour than cornstarch to thicken the same sauce (about one and a half times more),” she explains. “Flour is more stable to prolonged cooking than cornstarch.”

Flour and cornstarch also congeal at different temperatures, Mitchell points out.

“Wheat flour will gelatinize at a lower temperature, while cornstarch starts to gelatinize at a slightly higher temperature,” she tells Urbo.

This means your sauce will thicken up at a simmer with flour, but you actually need to cook it for a while to get rid of the raw flour flavor. If you use cornstarch, you’ll need to get the sauce almost up to boiling before any of its thickening powers activate—but you only need cook the sauce for another minute or so. After that, the cornstarch will break down, and you’ll be back where you started.

A sauce thickened with flour will have an opaque color and look relatively full and rustic (in other words, it’ll look like gravy), whereas a sauce with a backbone of cornstarch will be more transparent and have a light sheen (think stir-fry sauce). It’s all up to you and who you’re cooking for.

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Regardless of which you choose to use, be sure to mix either the flour or cornstarch in a cup with water (warm water for flour and cold water for cornstarch) before throwing it into the pan to help reduce any clumping. No one wants a lumpy sauce, and that’s a scientific fact.

You’ll also need to stir them constantly, since starches and water create a non-Newtonian fluid—essentially, a fluid that becomes more solid when exposed to pressure. That’s why you need to be careful when adding pure starch to any dish; as you stir, it’ll thicken significantly.

3. Little tweaks can help make your dream cookie.

There is nowhere to hide during the baking process. Sure, you may be able to somewhat fake it when you’re making dinner, but as soon as you bust out the cookie or cake recipes, the kitchen will show you no mercy. That being said, with some time, effort, and, yes, scientific know-how, you can master the pastry realm.

One thing most people have trouble with is making the perfect cookie. And by perfect cookie, we mean their perfect cookie. Crunchy, soft, thick, thin—everyone has their own cookie preference. If you’re stuck in a loop of unsatisfying results, it’s time to change up some ingredients.

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“Fats provides the flavor, richness, and add moisture to the cookie,” says Mitchell. If you want a different result, you have to make some changes. The fat you choose plays a big role in how much a cookie spreads in the oven, as well as its final texture.

“Butter melts quickly in the oven, so cookies with butter spread out more,” Mitchell tells Urbo. “If you use cold butter, it won’t spread as much before the cookie is done.”

Another option is to skip the butter altogether and use shortening. Shortening doesn’t melt as quickly, which means your cookies won’t be as thin as the ones made with butter.

The type of sugar, flour, eggs, salt, and baking temperature also all affect the final outcome as well. Try whole wheat flour for a denser cookie, for instance. Pick brown sugar to boost the chewiness factor. Generally speaking, higher temperatures and shorter cooking times lead to soft, chewy cookies, while low temps and long oven intervals create the perfect crispy crunch.

4. A pinch of salt can save a bitter brew.

You don’t have to be a total coffee snob to learn how to brew the perfect cup of joe, but there is a secret that most people probably don’t know about. When it comes to taste, the type of beans matter, the roast matters, and yes, the brewing process matters, but salt is really your secret weapon.

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Yup, good ol’ salt can really help boost the flavor of your brew. Actually, what it does is help cut down on bitterness. Now, you can’t bring an over-roasted, over-steeped, stale bean cup completely back to life, but a pinch of salt can help minimize and balance some of the bitterness and acidity.

Our bodies and brains have a complicated relationship with the sensation of bitterness. This particular taste is perceived slightly differently in our brains compared to sweet, salty, or umami tastes. For whatever reason, salt can to an extent cover up a bitter flavor. Science hasn’t quite figured out why salt works in these situations, but hey, science can’t have all the answers, okay?

If you’d like to try this brewing method, Alton Brown suggests adding a quarter teaspoon to every six tablespoons of coffee grounds.

5. To avoid onion tears, keep it sharp, breezy, and cold (or hot).

Time for the finale. How, oh dear scientists, can we avoid waterworks when cutting onions? There are a few ways, it turns out.

First, let’s make sure we understand the process. The reason that you start to cry while cutting up an onion is a type of amino acid called sulfoxide. When you break down the cell walls of an onion, enzymes are released, creating sulfenic acids. At that point, another chemical reaction occurs, and the sulfenic acids create a gaseous chemical (syn-propanethial-S-oxide) that causes you to tear up.

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The most successful way to minimize these chemical reactions (and the tears that come with them) is by causing minimal damage to the onion’s cell walls. That might not sound like an option; after all, you’re slicing and dicing, right? Well, according to physicist Dave McCowan, PhD, in an article for The Takeout, making quick, clean cuts with a sharp knife will limit the amount of tear-inducing chemicals coming from your onions.

Beyond staying sharp and fast, it comes down to managing the conditions, both of the onion and your cutting space.

“There are several solutions to the problem of onion tears,” biopsychology researcher Thomas Scott told the Scientific American. “You can heat onions before chopping to denature the enzymes. You might also try ways to limit contact with the vapors: chop onions on a breezy porch, under a steady stream of water or mechanically in a closed container.”

Oh, and if none of these work, you can always get a pair of super-stylish onion goggles.