DAVID POGUE: That delicious combination of stale bread, tasteless celery and tear-worthy onion: the stuffing!
First, you have to battle the onion.
BRIDGET LANCASTER: You know, the way you prepare onions has a huge impact on the end result. I want you to smell this onion.
DAVID POGUE: Um?
BRIDGET LANCASTER: You can't really smell anything, right?
DAVID POGUE: It doesn't have any smell.
BRIDGET LANCASTER: No.
DAVID POGUE: Have you done something to this onion?
BRIDGET LANCASTER: No, no, that's just a regular onion, but I'm going to show you something. So, if I just take this onion and cut it right in half, by taking the blade and slicing, I've started a chemical reaction. And now you can start to smell an aroma.
DAVID POGUE: Yes, I do.
BRIDGET LANCASTER: Yeah.
DAVID POGUE: It smells like onions.
BRIDGET LANCASTER: Onion.
DAVID POGUE: The more you cut an onion, the more of that chemical reaction happens and the stronger the taste.
Inside the cell of an onion there are enzymes. These are normally kept separate from the other molecules by a barrier. When your knife cuts the onion, these chemicals come together to form new molecules. Some make you cry; others create the strong onion flavor.
So you're actually changing the flavor of a vegetable according to the mechanical action of cutting it?
BRIDGET LANCASTER: That's right. The more you go at it and more you release those cell walls, the more flavor and the more pungent aroma is going to come out.
DAVID POGUE: One of the new molecules is propanethial-S-oxide, a volatile molecule that floats up and can trigger the tears.