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  • [ intro ]

  • Everyone knows the sadness of biting into a fresh piece of fruit

  • only to find the inside is dry and mealy.

  • It happens to lots of produce:

  • peaches, watermelons, tomatoes, you name it.

  • Some of the worst offenders are apples,

  • like those shiny Red Delicious

  • that are beautiful on the outside

  • and all grainy when you take a bite.

  • But these fruits aren't /inherently/ terrible.

  • They can start off yummy, and /become/ grainy.

  • And a lot of the problem has to do with the way they're stored.

  • When ripe apples are stored at cool temperatures,

  • like inside your fridge,

  • the cells making up the flesh of the fruit

  • unstick from one another.

  • But the tough outer walls of these cells stay strong,

  • so when you take a bite,

  • they don't break apart and release any juice.

  • So instead of a burst of flavor,

  • you just get that mealy texture.

  • That gets worse as the apple dries out.

  • Without moisture, the cells shrivel

  • and biting into those shriveled cells

  • is like trying to pop a deflated balloon.

  • The cells are less likely to burst and release their flavor.

  • And the more mature an apple is,

  • the more it dries out.

  • Plus, the cold air inside a refrigerator speeds up the drying process,

  • since it holds less moisture than warmer air.

  • So research suggests that if you want to save an apple for a few weeks,

  • your best bet is to pop it in the fridge right away,

  • before it becomes /too/ mature.

  • But the same rule doesn't apply to all potentially-mealy fruits.

  • Soft fruits, like peaches and nectarines,

  • can become mealy if you refrigerate them /too soon/.

  • That's because their mealy texture

  • is tied to the breakdown of a substance called pectin.

  • Pectin is a carbohydrate in cell walls that fruit generates as it ripens.

  • It strengthens cell walls

  • and makes them stick together.

  • But pectin can dissolve in water.

  • And over time, as it dissolves,

  • the cell walls lose their strength.

  • In some fruits, pectin doesn't /just/ dissolve, either

  • it also gets broken into pieces by enzymes.

  • And that's a good thing.

  • Under normal conditions,

  • the cell walls weaken through these processes,

  • and the fruit becomes nice and soft.

  • When you bite into it,

  • the cell walls burst and release their juice.

  • Like a proper fruit.

  • But as soon as you stick these fruits in the fridge,

  • that natural process starts to veer off track.

  • In general, low temperatures slow down chemical reactions,

  • so if you keep fruit cold,

  • its pectin molecules break down less.

  • And /that/ means the cell walls hold up when you bite into them,

  • so whole cells break apart, rather than bursting.

  • And you get a sad, mealy mouthful.

  • But not all fruits will come out of the fridge equally pathetic.

  • Different kinds have different compounds

  • attached to the pectin molecule,

  • so they often ripen differently.

  • And as a result, they /also/ react differently to refrigeration.

  • Still, as a general rule,

  • fruits that continue to soften after they're harvested

  • like peaches, nectarines, cantaloupe, and tomatoes

  • should only be refrigerated /after/ they're fully ripened

  • if you want to avoid that gross, grainy texture.

  • Unfortunately,

  • you can't always know what happened to your fruit before it got to the store.

  • And from the outside,

  • it's impossible to tell which fruit already has a mealy texture.

  • But you can make sure it's not your fault that it becomes mealy by storing it at the

  • right time.

  • Thanks for watching this episode of SciShow!

  • If you liked this episode

  • and you want to learn about another reason we end up with disappointing fruit,

  • you might be interested in this video about why apples turn brown.

  • You can watch that one next!

  • [ outro ]

[ intro ]

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B1 中級

是什麼讓水果變味? (What Makes Fruit Mealy?)

  • 4 1
    林宜悉 發佈於 2021 年 01 月 14 日
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