Water irreversible structural transitions, heating

In starch, disruption of the ordered granular structure when heated in a solvent (usually water) is called destructuration or gelatinization. The temperature at which this occurs increases as the amount of solvent is decreased and is seen as an endothermic peak during the first scan in DSC. Destructuration is an irreversible transition and, after cooling, an amorphous entanglement of amylose and amylopectin is formed. 

Fig. 3. Differential scanning calorimetry scans of biomembrane transitions, all obtained with 50% ethylene glycol/water as solvent. (A) A. laidlawii membranes from cells grown in tryptose medium at 37 C (B) lysodeikticus membranes from cells grown in brain heart infusion at 37 C (C) JE. coli K12W945 whole cells grown in minimal salts with glucose at 20 C (D) the same cells as in (C), but scanned after thermal protein (E) rat liver microsomes (F) rat liver In all cases a lower temperature reversible lipid transition is followed by a higher temperature irreversible protein peak. The protein denaturation peaks are featureless in (A), (E), and (F), but show fine structure in (B), (C), and (D). Unlike other organisms, coli after heating shows two lipid transitions and residual reversible protein denaturation, as seen in (D).

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