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Old 04-22-2006, 09:29 AM
EricT EricT is offline
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Join Date: Jul 2005
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In case anyone is wondering why this "waxy maize starch" is digested quicker and has a higher glycemic index than, say, regular corn starch, or maltodextrin (which is pretty darn high) is is because it is high in AMYLOPECTIN. Starches are usually made up of Amylose and Amylocpection.

Here is part of an article by Dan Duchaine which provides a handy explanation:

You can see that white table sugar has a moderate GI of only 65. As you will learn, many starches have a much higher GI than sucrose. Unlike starch, which uses only the alpha-amylase-glucosidase enzyme, many sugars are cleaved by other enzyme, which are less efficient. Also, both galactose and fructose are not immediately converted into glucose but have an intermediate conversion (needing additional enzymes) to glycogen in the liver. Scientists have long assumed that the highest GI foods were the mono- and di- saccharides. This is not correct. The highest GI carbohydrates are the glucose oligomers, which are starch chains between three and ten glucose molecules long, 9 such as commercially available maltodextrins derived from cornstarch. This is an embarrassing admission — I was involved in the introduction of maltodextrins into the sports supplement market in 1981, heralding them as the newest "complex carbohydrates."

Factors that Affect the Glycemic Index

GRAIN PROCESSING: The less processed a grain is, the smaller the surface area. Finely ground wheat flours might make attractive-looking, soft breads, but they are digested very quickly and thus have a higher GI.

GELATINIZATION: Inside a grain, starch molecules are grouped into dense structures called granules. Gelatinization occurs when water and heat cause the granule to swell, exposing more surface area. With enough water and heat, some starch molecules will break off, which is what happens when you heat water and wheat flour to make gravy.

STARCH COMPOSITION: There are two basic starch structures: amylose and amylopectin. Amylose is simply a straight string of glucose molecules. It looks like this:

0—0—0—0—0—0—0

Amylose is broken down slowly from the ends, like it is being eaten by Pac Man in slow motion. Amylose is also called "resistant starch" because only about 40% can be digested. Most starches have some amount of amylose in them. Uncooked cornstarch has about 70% amylose. Some types of rice have 28%; others have only 2%. The higher the amylose content, the lower the GI. Unlike the mock carbohydrates in the old starch blockers (or the prescription drug acarbose), amylose is not easily fermented. Starch blockers dump fermentable starch into the colon, causing, in polite medical language, "meteorism" (which is projectile vomiting from the opposite end).

Amylopectin, the more complex starch, has a structure that looks like this:
0
1
0
1
0—0—0—0—0—0—0—0—0
1
0
1
0
Every four or so glucose molecules, the chain branches. In this structure, our Pac Man-like enzymes can chomp away at the end of every glucose chain. There is more exposed area for the enzymes to attack, so amylopectins generally are digested faster and therefore have higher GI's.

There is one instance when this isn't true. Some new maltodextrins (usually fragmented amylose) are reduced amylopectins. A straight-chain maltodextrin has a high GI, but a branched-chain maltodextrin has a lower GI, which is why I like to use them in diet meal-replacement powders.
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If you act sanctimonious I will just list out your logical fallacies until you get pissed off and spew blasphemous remarks.
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