Starch disruption

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. 

There are five prime factors that determine the properties of starches 1. starch is a polymer of glucose (dextrose) 2. the starch polymer is of two types linear and branched 3 the linear polymeric molecules can associate with each other giving insolubility in water 4. the polymeric molecules are organized and packed into granules which are insoluble in water and 5 disruption of the granule structure is required to render the starch polymer dispersible in water. The modification of starch takes into account these factors. 

Just about any soluble powder that is not disruptive to the body can be used, such as baking soda, pow-dered sugar, powdered milk, starch, etc. 

In the 1940s, researchers identified that when starch is heated in water there were three distinct stages in the granule disruption process. During the first phase, water is slowly and reversibly absorbed by granules. 

Putaux, J. -L., Molina-Boisseau, S., Momaur, T., Dufresne, A. (2003). Platelet nanocrystals resulting from the disruption of waxy maize starch granules by acid hydrolysis. Biomacromol, 4,1198-1202. 

When starch is heated in excess water, the crystalline structure is disrupted (due to breakage of hydrogen bonds) and water molecules become linked by hydrogen bonding to the exposed hydroxyl groups of amylose and amylopectin. This causes an increase in granule swelling... 

Starch gelatinization is the disruption of molecular orderliness within the starch granule. It results in granular swelling, crystallite melting, loss of birefringence, viscosity development, and solubilization. 

DSC studies have shown that modification alters thermal transition temperatures and the overall enthalpy (AHgei) associated with gelatinization (Tables 10.13 and 10.14). Upon hydroxypropylation, the reactive groups introduced into the starch chains are capable of disrupting the inter-and intra-molecular hydrogen bonds, leading to an increase in accessibility by water that lowers... 

The crystallinity of starch granules is disrupted during derivatization (Saroja et al., 2000), and this leads to a greater degree of separation between the outer branches of adjacent amylopectin... 

In a comparison of RDS, SDS, and RS formation in cooked-cooled potatoes that were intact, coarsely minced, pasted or finely dry-milled the extent of tissue disruption appeared to have little influence on the formation of SDS and RS after cooking (Mishra et al., 2008). The formation of SDS and RS is likely to be more a manifestation of the structure of the starch molecules involved without any constraints imposed by the starch-containing tissue. 

Lipids in starchy foods may occur in the free as well as bound forms. The latter being either in the form of amylose inclusion complexes or linked via ionic or hydrogen bonding to the hydroxyl groups of the starch components. Free lipids are easily extractable at ambient temperatures, while use of nonalcoholic solvents for a prolonged period or disruption of the granular structure by acid hydrolysis (see Basic Protocol 4) may be required for the efficient extraction of bound lipids. While acid hydrolysis allows the release and quantitation of lipids, the procedure leads to destruction of the starch components therefore, the alcohol extraction system involving propanol and water would be most desirable in these cases. This system removes both nonpolar and polar lipids from samples. 

Fig. 38.—Disruption of potato starch in an electrolyzer (50°C) under acidic (—) and alkaline (- -) conditions (from Ref. 322).

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