To the naked eye under the room lights, I wasn't able to see the difference between the plain-water and lemon-water samples at all. For comparison's sake, note the white table surface underneath, which is a uniform shade of white, but in the photos appears darker at left as well. Fifteen minutes later, and differences are already becoming more apparent—the light source at the right alone isn't responsible for the yellowing of the untreated apples on the top row at left. At 30 minutes, we have more significant browning of the plain apple slices.
The plain-water sample in the bag at far left is maintaining its color better, but not as well as the citric acid samples in the two rightmost bags. The lemon-water sample second from left is not very different from the plain-water one, and definitely more yellow than the citric acid—treated samples.
Note also the slight pink tint in the citric acid solutions, from pigment being leached out of the apple skins. Jumping ahead to one hour after the first photo, the differences become more stark.
The plain-water and lemon-water slices are holding up better than the air-exposed pieces of plain apple, but they don't look great. If you ate a slice of any of the water-soaked samples at this point, you'd notice that the apples had become waterlogged and slightly mushy. Take a look at the above photo. That's an image of the same samples after three hours and 15 minutes. At this point, the lemon-water sample second from left in the bottom row has browned more than the plain-water sample; this lines up with scientific studies I've read, which have reported increased browning when the apple is exposed to lower concentrations of ascorbic acid.
Meanwhile, the citric acid samples look practically bleached, while the skins have taken on a neon quality as even more pigments have been drawn out. At this point, all the samples were near inedible. The citric acid ones, of course, were inedible from the start unless you like the idea of Sour Patch Kid—style apple slices. The plain- and lemon-water apples, meanwhile, had reached an undesirable level of browning, and both were waterlogged and unpleasant to eat.
The lemon water also subtly altered the apple flavor with a distinct citrusy quality. I later did a series of tests with much lower concentrations of citric acid one teaspoon per quart of water , which I found more palatable, but they didn't work nearly as well at preventing browning.
I wasn't able to find a concentration of citric acid that prevented browning well enough while also not tasting overly acidic. I also did a test of simply rubbing a cut lemon all over the cut surface of an apple. You can see a photo of that below in the salt section, but I'll sum the results up now: Skip it, since it adds a heavy lemon flavor to the apple and only marginally reduces browning.
My take on this: Soaking apples and pears is a method that works fine if you use plain water, but only for a very short time—I'd say less than 30 minutes, and ideally less than Any longer, and your fruit will brown while the texture suffers.
Lemon water, meanwhile, actually speeds up browning while changing the apple's flavor, so avoid it. Check out the time-lapse GIF below to see the apples brown over time like Gertrude's poem, it goes round as around as an apple Sodium chloride, or common table salt, is another chemical that can interfere with oxidation. For my test, I soaked apple and pear slices for 10 minutes in a salt solution made from half a teaspoon of Diamond Crystal kosher salt dissolved in one cup of cold water.
I then drained them and let them stand for two hours alongside samples of untreated cut apple. In the photo above, the saltwater-soaked apple is on the bottom right, with two untreated apple samples to the left. The top row contains my lemon-rubbed apple, at right, and its untreated control at left. As you can see, the saltwater apple resisted browning the best; even after two hours, when this photo was taken, it was still a respectable white color.
The salt flavor is very mild on the surface of the apple—one taster didn't even notice it—but it's there. The good news is that a quick rinse under cold running water completely washes away any traces of salt, leaving you with a fresh-tasting and -looking apple, well after it's originally cut. Why is that? There is something in apples called PPO polyphenol oxidase , which is an enzyme.
Enzymes are things that do all the work to make sure cells can live their life. Once you cut into an apple you are opening up some of the cells inside it. The PPO enzyme reacts to the oxygen in the air and starts to turn the apple brown. This enzyme is common in plants, and is also the reason that potatoes, pears, and bananas turn brown once they are cut and exposed to the air too. These apple crumble dippers are quick to make and they are really good for you.
Make sure your grown-up supervises you so you know how to grind them up until they are powder. Mix in all the other ingredients apart from the butter. Melt the butter in the microwave. Your grown-up can cut the apples into 1cm thick slices while you are doing this. Dip an apple slice into the melted butter, and shake off any drips. Put it into your powdery mix, and move it around until coated. Pop it on the wire rack.
Continue to do this until all the mix or apples are used up. Try dipping them in:. The moment a knife slices through apple—spilling the contents of apple cells along the surface of the cut, and allowing everything to mix—a reaction begins.
In particular, an enzyme known as polyphenol oxidase that had been held in check is loosed. Almost immediately, it begins altering polyphenols, a group of health-promoting chemicals with antioxidant activity that naturally occur in apples and other produce. It is believed that this reaction, called enzymatic browning, is a form of plant defense against pests and pathogens, says Hartel.
Some of the chemicals created via this reaction have been shown to help ward off invading organisms.
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