Name: 【TED-Ed】Are spotty fruits and vegetables safe to eat? - Elizabeth Brauer
Uploaded: 2016-09-25T23:32:13.000Z
Duration: 4 min 9 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

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.

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.

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.

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

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

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,

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

One toxin coronatine makes plants' stomata open up,

Coronatine also activates pathways leading to chlorophyll degradation,

As the bacteria continue to feed and multiply,

That explains spots, but what about mushy blemishes?

Those are usually caused when the fruit is attacked by microbes

If the plant is wounded during transport,

necrotic fungi can infiltrate  through the wound,

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,

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,

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.

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.