Wednesday, December 01, 2004

Water Activity


The question was posed last night over Taco’s by our resident funny man.

Why does bread go stale, but biscuits go soggy?

It’s an important point and one that I’m sure we’ve all pondered. Water activity, my bloggy friends, water activity. Now, I’m not talking frolicking around in your string bikini (although I’m pretty sure after Friday night’s encounter, many of you would be willing to don said bikini, and I ain’t jus’ talkin’ ‘bout da ladies). I’m talking about equilibrium.

Chemistry is all about being equal and sharing what you’ve got to be something bigger and better. I think we can all learn a little something from this. Don’t you?

Let’s take water for example. If Mr Hydrogen and his twin brother, let’s call him… Mr Hydrogen weren’t willing to share their single electron with Ms. Oxygen (nice – two men, but weird because they’re twins) we wouldn’t have water and we’d be up the non-existent creek.

“But,” I hear you thinking, “I wouldn’t consider having soggy biscuits and stale bread ‘working for the greater good’!” No. And it’s a good point. However, I didn’t say that Chemistry is always working for us (think petrol, atom bombs, cyanide), it’s just working for Chemistry.

So your bread is sitting there in the air where the relative humidity is at… hmmm… 65% (that’s average).

Your bread has an aw (water activity) of 0.95. (aw (water) = 1.0)

The biscuit has an aw of 0.3.

If you compare the two you’d have to admit the bread is fairly moist.
*nodding*
Even compared to the relative humidity of the room (which is measured on a different scale, I know, but it’s helping my point… I think)
*mutterings of agreement*.
Great.
And so then you’d say that the biscuit on the other end of scale in having a low aw
*uh huh – get to the point*.
OK. Yeah.
Thus, if everything is trying to be equal with their surroundings the water is going to osmotically move out of the bread and into area with there is a lower concentration of water (the air).
And the biscuit is going to drawn moisture from the air into, as the air has a higher concentration of water than the biscuit.

If you don’t believe me, I don’t really care. I know I’m smart. But you can experiment yourself. Put a slice of bread and a biscuit (both fresh) into a sealed air tight container and leave for a good couple of days. The biscuit and the bread should end up having a similar texture… apart from the obvious – one’s a biscuit and one’s a slice of bread.

9 Comments:

Blogger Lee Lee said...

So this is what food technologist muse over by the water cooler, eh? I’ve always wondered.

12:04 pm  
Blogger Sherriff said...

I was trying to think of some genius, witty remark..but I just couldn't. Dough!

2:45 pm  
Blogger sugar and spice said...

oh, sheriff.

you and your half-baked comments.

thanks for the (presumed) compliment, i really kneaded a pick-me-up.

3:48 pm  
Blogger Lee Lee said...

One more pun out of your two and I’ll give you a right baking!

4:19 pm  
Blogger knifey said...

there is no way i could leave a biscuit or a piece of bread two days without eating them.

no way in hell.

4:40 pm  
Anonymous Anonymous said...

Enough crustiness you two, he was just trying to get a rise. Stop loafing around and milling about, say sorry with a nice bunch of flours. It's the yeast you can do.

(sorry.)

6:31 pm  
Blogger sugar and spice said...

i bow down before you anon

8:25 am  
Blogger Lee Lee said...

Ha ha ha! Anonymous poster whom has stolen the crown of Dad Joke puns from Sheriff, reveal thy self at once! Your ass whipping quips berate his attempts at humouring us!

8:38 am  
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