|MadSci Network: Chemistry|
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 line...off 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. (firstname.lastname@example.org) Best Regards, Mike
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