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Old 09-10-2010, 01:33 AM   #1
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Default Denaturing of amylose and amylopectin?

Does anyone have any information on if/at what temperature starch begins to denature? I've done searching on Google and can't seem to find too much that isn't related to the amylase enzyme, but if there's any chemists around, I'd love to know.

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Old 09-16-2010, 01:43 AM   #2
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I'm afraid there's a good reason you can't find an answer using google: your question doesn't make sense. "Denaturing" is, definitionally, a process which occurs to proteins. The things you've mentioned area all polysaccharides.

Maybe if you describe what you're wondering about, someone can help you with the terminology to use when googling.

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Old 09-16-2010, 07:03 PM   #3
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Denaturing was definitely not the right word. I think "thermal decomposition" would be a better term. I was wondering at what temperature the sugars breakdown. Do they isomerize into varying compounds at different temperatures?

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Old 09-16-2010, 07:20 PM   #4
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Most sugars don't do much until they hit ~400F and they caramelize, not breakdown.

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Old 09-16-2010, 07:35 PM   #5
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Quote:
Originally Posted by david_42 View Post
Most sugars don't do much until they hit ~400F and they caramelize, not breakdown.
"Carmelization" is the name we give to a slew of different thermally induced reactions of sugars, including some that might be considered "decompositions". Sugar inversion is also part of carmelization, and happens pretty easily in the 350F range. I'm not sure the author is actually interested in simple sugars, though -- he (or she) original specificed amylose and amylopectin, which are both long-chain polysaccharides (which wouldn't normally be called "sugars".) Maybe he[/she] can provide some clarity on this point?
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Old 09-16-2010, 09:07 PM   #6
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Are you perhaps referring to gelatinization temperature i.e. the temperature at which the starch granules burst releasing their contents to the solution? If so that depends on the makeup of the matrix i.e. on the grain. For example, rice has to be cooked at pretty high temperature before its starches are capable of attack by enzymes whereas barley malt is adequately gelatinized at above, saym 140 °F.

Or do you mean inversion in which a sucrose molecule is hydrolyzed into glucose or fructose?

Or perhaps Maillard reactions in which mellanoidins are formed from sugars and amino acids?

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Old 09-16-2010, 10:46 PM   #7
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How about:

Quote:
Chemical reactions for the samples started around 300 °C to generate ether and ethylene segments via thermal condensation and dehydration mechanisms. Heating at increased temperatures generated substituted phenol/benzene and furan structures with methylene or ether linkages between these aromatic rings. Varied thermal reactivity was observed for starch samples around 300 °C due to their difference in molecular weight, pH or structural modification. However, the reaction pathway was similar. Above 400 °C, the starch structure was destroyed and the product appeared structurally similar to thermally cross-linked/decomposed phenolic/furfuryl alcohol resins, thereafter, the thermal reaction of the systems followed a similar pathway as these resins. No significant difference of chemical structures was obtained for the four samples after heating above 350 °C and identical carbon structures were generated at 600 °C.
Thermal decomposition chemistry of starch studied by 13C high-resolution solid-state NMR spectroscopy

Xiaoqing Zhang, Jacob Golding and Iko Burgar
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