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  • In 2010, $30 billion worth of fruits and vegetables

  • were wasted by American retailers and shoppers

  • in part because of cosmetic problems and perceived spoilage.

  • That's a poor use of about 30% of the produce on the market,

  • not to mention the water and energy required to grow and transport it,

  • and the landfill space getting used up by rotting fruit.

  • So what are those cosmetic problems?

  • You've probably passed over a spotty apple in the grocery store,

  • or accidentally sunk your thumb into a mushy patch on a tomato.

  • These blemishes can doom produce to the trash can.

  • But what are they anyway,

  • and are they actually bad for you?

  • Those spots are evidence of an epic battle between plants and microbes.

  • Like humans, plants coexist with billions of fungi and bacteria.

  • Some of these microbes are beneficial to the plant,

  • suppressing disease and helping it extract nutrients.

  • Others are pathogens, attacking the produce,

  • still alive as it sits in a store display or your refrigerator

  • and siphoning off molecules they can use themselves.

  • The good news is they're almost never bad for you.

  • These fungi and bacteria have spent millions of years

  • developing strategies to overcome a plant's immune system.

  • But healthy human immune systems are different enough

  • that those strategies just don't work on us.

  • So in a plant, what does this process look like?

  • Microbes can reach plants in a number of ways,

  • like getting splashed onto it during watering or fertilization.

  • Under the right conditions,

  • the microbes grow into large enough colonies

  • to attack the waxy outer layer of fruit or leaves.

  • Their target: the delicious sugars and nutrients inside.

  • This type of pathogen often makes spots like this.

  • A clump of bacteria drains the nutrients and color from the fruit's cells

  • making that yellow halo.

  • It then moves outward,

  • leaving a black spot of dead cells in its wake.

  • Each spot, which could contain hundreds of thousands of microbes

  • is actually caused by a combination of microbial attack

  • and the host defending itself.

  • For example, this is the bacterial pathogen Pseudomonas syringae.

  • Once on a tomato, it enters the fruit and leaves,

  • multiplies in the space between the cells,

  • and produces toxins and proteins

  • that allow it to disrupt the plant's immune response.

  • One toxin coronatine makes plants' stomata open up,

  • allowing bacteria to enter more freely.

  • Coronatine also activates pathways leading to chlorophyll degradation,

  • which you can see as yellow spots.

  • As the bacteria continue to feed and multiply,

  • they start to kill off the plant cells.

  • That explains spots, but what about mushy blemishes?

  • Those are usually caused when the fruit is attacked by microbes

  • after it's detached from the plant.

  • If the plant is wounded during transport,

  • necrotic fungi can infiltrate through the wound,

  • kill the cells,

  • absorb their nutrients,

  • and leave your food looking mushy or brown.

  • Those spots in particular can taste pretty bad.

  • You're eating dead and decomposing tissue, after all.

  • But you can usually salvage the rest of the fruit.

  • The non-mushy spots, like the ones you typically see on apples or tomatoes,

  • are just on the surface and don't usually affect flavor.

  • Of course, microbes that do make us sick, like E. coli and salmonella,

  • can hitch a ride on vegetables, too.

  • But because they're not plant pathogens, they don't typically cause spots.

  • They just hang out invisibly on the surface.

  • So it's washing fruit and veggies, not avoiding the spotty ones,

  • that will help you avoid getting sick.

  • So the next time you're at the grocery store,

  • don't be afraid to pick up funky-looking fruit.

  • Some stores will even give you a discount.

  • Wash them well and store them properly,

  • as some produce like apples and cabbages will keep in the fridge for weeks.

  • The spotty ones may not be eye candy, but they're safe and just as delicious.

In 2010, $30 billion worth of fruits and vegetables

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TED-ED】スポット的な果物や野菜は食べても安全?- エリザベス・ブラウアー (【TED-Ed】Are spotty fruits and vegetables safe to eat? - Elizabeth Brauer)

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    VoiceTube に公開 2021 年 01 月 14 日
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