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  • If you've ever made gelatin for a picnic or party,

  • maybe you've been warned not to add certain fresh fruits, like kiwi or pineapple.

  • And for good reason. Add these foods to your gelatin, and it won't set.

  • It will remain a big, goopy mess.

  • The reason why is pretty straightforward, but if you understand it,

  • it can help you learn how to make better desserts,

  • and how to up your cooking game in general.

  • To understand why these fruits ruin gelatin, you need to know what this stuff is made of.

  • Once it sets, gelatin is basically a mesh of interconnected collagen molecules.

  • Collagen is a long, fibrous protein found in things like skin and bones.

  • Andyes, the collagen in gelatin does traditionally come from animals.

  • Manufacturers boil things like hides or bones until the proteins come out,

  • and then they turn them into a powder you can buy at the store for, like, a dollar.

  • When you dissolve the powder in hot liquid, the collagen separates into individual fibers.

  • Then, as the solution cools, those fibers start to bind to one another

  • and gradually form a mesh.

  • But if you add certain fruits as you're making your gelatin,

  • the last process will never happen.

  • It's because fresh kiwi, pineapple, and some other fruits

  • contain high concentrations of proteases, or proteolytic enzymes.

  • These are substances that digest proteins, basically, chopping them into tiny pieces.

  • If this stuff gets into your gelatin mix, it will cut up those strands of collagen

  • until they're too short to link together, so your dessert will come out looking like a soup.

  • If you know why this happens, though, it's easy to find some ways to work around it.

  • For one, if you cook the fruit, the heat will inactivate those enzymes,

  • so your gelatin will turn out just fine.

  • This is also why something like canned pineapple doesn't cause issues.

  • Alternatively, you could make your dessert with agar instead of gelatin.

  • Agar is made from certain types of red algae, and like gelatin,

  • it forms an interconnected meshwork of fibers.

  • But it's made of carbohydrates, not proteins, so proteases won't digest it.

  • Of course, while these fruity enzymes aren't great for gelatin, they do have their uses.

  • For one, they have some surprising industrial and medical benefits.

  • Like, they can be used to prep damaged areas for skin grafts if someone gets a severe burn.

  • The treatment breaks down and clears away dead and damaged tissue.

  • But maybe more importantly to you, you can also use juice or pulp

  • from protease-containing fruits in the kitchen to tenderize tough cuts of meat.

  • The enzymes break down stringy bundles of proteins, making the meat easier to chew.

  • So go ahead and save that fresh pineapple for your steak,

  • and stick to the canned stuff when it comes to gelatin. Everyone will thank you.

  • If you want to learn more science-inspired cooking hacks,

  • we've got an episode with seven more of them for you.


  • And as always, thank you for watching this episode of SciShow!

If you've ever made gelatin for a picnic or party,


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菠蘿和獼猴桃為什麼會破壞明膠? (Why Do Pineapple and Kiwi Ruin Gelatin?)

  • 21 1
    林宜悉 發佈於 2021 年 01 月 14 日