Thursday, January 8, 2009

Eureka! Applesauce!

So I have never successfully made applesauce. Back when Evelyn was a toddler I took a stab at it. We had some very hard, sour apples and I thought, hey, I could make applesauce with these. I don't have a recipe, but really, how hard could it be?

I peeled and chopped them up, tossed them into the pot, covered them with water and, since they were so sour, I threw in some sugar. I turned on the burner and waited for them to turn into mush.

And waited.

And waited.

And they never did. They never lost their shape.

I decided applesauce was created by weird alchemy beyond my powers and gave up.

Years later Clementine went to a friend's homeschool program where she made and learned to love applesauce. And she would have been happy to slurp the whole giant jar of homemade applesauce my friend Jennifer sent us. So I thought we'd revisit this culinary nemesis.

Clementine happened to get a book called The Inquisitive Cook for Christmas. The subtitle is "Discover How a Pinch of Curiosity Can Improve Your Cooking". I had a pinch of curiosity about applesauce, so on a chance, I opened up the index and to my delight found applesauce listed.

I flipped to the page, to find: "Have you ever wondered why you were taught to add the sugar to the applesauce after the apples have cooked?"

No, I had never wondered, because somehow I grew up without this vital and potentially life-changing piece of information.

All the jars of applesauce that might have been flashed before me.

And here is the reason you add the sugar after: If there is sugar in the apple cells, and none in the water, the water rushes into the cells to dilute the sugar, and pop! go the cells. This, I am told, is called stewing.

If there is just as much or more sugar outside as inside the water doesn't move into the cells and doesn't pop them. And the apples don't turn to mush. They are preserved in syrup. This, I am told, is called poaching.

So, a little wiser, we started making applesauce.

I love my peeler-corer. It peels, cores and slices an apple in 30 seconds flat.

Clementine finished up the chopping, taking pains not to let any raw apple touch her.

Greta had no such issues.

We put all the apples in a pot, covered them with water, and began waiting with bated breath.

Which got old fast. So we read on in the book about why apples brown. It turns out that iron-containing polyphenols combine with oxygen to form melanins (brown pigments).

So this sounds too complicated but some polyphenols are known to us by other names: tannins (found in tea, red wine and redwood bark) and flavonoids which are touted as antioxidants and are found in coffee, tea, chocolate, citrus.

So anyway, these iron-containing polyphenols combine with oxygen in the air. An enzyme called polyphenol oxidase speeds up this reaction. I didn't realize this was an enzyme catalyzed reaction. Many of you may not know this but Biochemistry makes me weak in the knees. I love it that much. So now I am extra excited about browned apples.

Look, I wrote a little equation:

Polyphenols with Iron + Oxygen ---polyphenol oxidase---> Brown Apple Slices

So we brainstormed about how to stop the browning. Eventually the girls came up with 3 strategies, and several tactics for each, some practical, some not:

Get rid of the iron:

  • Evelyn jokingly proposed a very strong magnet
  • She also proposed genetically modifying the apples to not contain iron (nutritionally questionable!)
Get rid of the oxygen:
  • Clementine suggested putting it in a vaccuum and Evelyn suggested putting it in a jar with lit candle to burn up the oxygen.
  • Covering it with water

Get rid of the enzyme polyphenol oxidase:
  • Slow its action by refrigeration
  • Clem suggested we genetically modify the apple to not produce polyphenol oxidase. Believe it or not this is being done.
  • Mess up the enzyme so it doesn't work anymore: by cooking. The fancy word for this is denaturing the enzyme. A link to a protein folding game called FoldIt landed in my inbox and I am planning on taking a look with the kids. Not only do you learn about protein folding, but you also help scientists figure out the native state of proteins.
  • Make the enzyme bind with something else: lemon juice (this one we also read about in the book, or rather, we knew this works, but didn't know why).

So we cut slices and submerged one, refrigerated one, put one in a jar with a candle, put lime juice on one, we counted our apple sauce as cooking a sample, and we had a control.

The lime juice prevented browning best. Cooking prevented browning, but really changed the appearance. The samples that were refrigerated, submerged and in the jar with the candle, showed some browning, but not as much as the control.

I got volunteered to taste all the samples. No one else was willing. The control was not only browned but a bit mushy. The submerged sample was mushy and tasteless. The sample in the jar had taken on the lavender flavor of the candle, and was a bit mushy. The refrigerated sample was a bit rubbery and fridgy tasting (note to self: clean out fridge). The lime sample stayed crisp and had a pleasant citrusy taste. It tasted best. The cooked apples were mushy in a good way.

And that is why there was no lack of volunteers to eat the applesauce.


Anonymous said...

what a cool project? Can we come over and have some?

And btw, Maggie is a big fan of raw apples but will NEVER touch a cooked one....

AM said...

Wow, that's really interesting!

As a related aside, tannin-containing drinks inhibit the absorption of iron from non-heme (plant) sources. So don't drink tea with your cream of wheat.

patricia said...

I love how you turned a simple cooking project into an opportunity to make scientific hypotheses. Who knew apples could lead to such sophisticated wondering?

Christine said...

I have to agree with Patricia, love the science in this piece........just like the show on foodnetwork... I think is called GOOD EATS

oh btw, BTE = big time engineer.....He doesn't want his name on the interweb :P

Hope to see you soon.....10 mins remember!