MadSci Network: Chemistry

Re: Why does pudding work? Explain the chemical reaction occurring.

Date: Mon Feb 7 21:55:38 2000
Posted By: Michael Weibel, Battelle Chemist
Area of science: Chemistry
ID: 948939483.Ch

Hi Elaine.
Cooked puddings utilize starches to thicken them.  A typical cooking 
starch you might recognize is Corn Starch, which is a common ingredient in 
cooked puddings.  When you use this starch, you generally dissolve it in 
water (it's not very soluble (dissolvable), is it?  If you've ever tried 
to dissolve it by itself in water, you notice a crunchy/slippery non-
dissolved but slightly moistened sludge on the bottom of the container) to 
help distribute it in whatever you're cooking (prevents lumps).  You may 
have noticed that corn starch doesn't appear to work until what you're 
cooking gets pretty hot.  What's happening is that the molecules of starch 
are like long strings and become tangled.  It taked heat from them to 
really get moving around so that they tangle well (the hotter, the faster 
they move).  When they become tangled, they "tie up" water in their 
tangled structure.  This makes a phase called a "colloidal gel", not so 
different from the hair gels you may have seen.  You can imagine this at a 
molecular level as being like a box full of slinkies and marbles.  If you 
shake up the box really hard, all the Slinkies will become tangled (the 
starches) and many of the marbles (water molecules) will become tied up in 
the tangled mess.

Sometimes, gelatin is used as a thickener (Jello, for example).  Gelatin 
used to be an animal product (remember the to the glue 
factory?  They made gelatin there as well...ground up bones as I recall), 
but now may be a synthetically produced product.  It operates in a similar 
way, tying up water in a gel.

I hope that I have answered your question.  Please feel free to contact me 
if you have further questions.  (

Best Regards,

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