Science World Blog How Do You Find a Nice Pear?
How Do You Find a Nice Pear?
Last Updated (Sunday, 13 November 2011 23:19) Written by Raymond Nakamura
Lately, my appreciation has been growing for a nice pear, one of the three thousand varieties of Pyrus communis. But sometimes they're either too hard or too mushy. I decided to see if a little science could improve my odds.
The Time is Unripe
The hardness issue comes from pears always being picked before they are ripe. This makes them easier to transport. But even if you have a pear tree in your backyard (with or without a partridge), if you wait until the pears look ripe, they will be mushy inside, because they ripen from the inside out when attached to the tree.
Put a Bag on It
To ripen pears properly, you're supposed to leave the pears in a paper bag or a fruit bowl at room temperature for a few days. They are ripe when they give in to a little to pressure near the stem.
We are Just Pawns
What we consider fruits are the swollen ovaries of a pollinated flower. Ripe fruit is a plant's way to get dumb animals like us to spread its seeds. Technically, in a pear, the true fruit is only the core with the small black seeds; the edible part is formed from the stalk, but let's not get that picky.
It's a Gas, Gas, Gas
In pears and other climacteric fruits, the key to ripening is a simple organic compound called ethylene. Grapes, strawberries, citrus and other non-climacteric fruits don't rely on ethylene as much and must stay attached to the plant to ripen.
In From the Cold
But back to pears. Environmental stresses, damage to the fruit, or more ethylene can trigger ethylene production and start ripening. Cold storage conditions commercial pears for ethylene production when you bring them home.
Change is Good
Ethylene sets off the production of various enzymes that make fruits delicious. Hydrolases break down chlorophyll, so the fruit loses its greenness and red and yellows take over, although many pear varieties stay green. Hydrolases also break down large organic molecules into smaller ones that float into our noses as fruity fragrances. Pectinase breaks down the pectin that glues cells together, so the fruit becomes softer. This is a big difference in ripe pears. Kinase breaks down acids, so the fruit becomes less tart. Amylase breaks down starch into sugars, so the fruit becomes sweet. Pears contain the highest amounts of levulose, the sweetest natural sugar. My mouth is watering just writing about this. Do you have a favourite pear variety?
More Info
I just read The Shallows about how the internet makes your head bounce around too much. So I'm putting some links at the end, if that helps.
Climacteric vs. Non-climacteric
A Pear Ripening Science Fair Project