Starch crystallization

Zobel, H. F. (1988b). Starch crystal transformations and their industrial importance. Starch/... 

Presence of native starch crystals. In plant materials, starch exists as semicrystalline, granular entities. Starch molecules, both amy-lose and amy lopectin, with their many intermo-lecular hydrogen bonds, give structure to the starch granule (Zobel, 1988). The crystalline regions formed by this intermolecular hydrogen bonding are somewhat resistant to enzyme hydrolysis and need to be broken prior to enzyme treatments. 

The structure of A-type starch crystals was derived through the joint use of electron diffraction of single crystals, x-ray powder patterns decomposed into individual peaks, x-ray fiber diffraction data and extensive molecular modeling32 (Figure 5.5). The density calculated for the crystalline region (d = 1.48) is reasonably close to the observed density, and indicates that there are 12 glucosyl units and 4 water molecules in the unit cell. Intra- and inter-molecular energy calculations showed that... 

Conditions required to generate A- and B-type crystal conformations are reasonably well-understood. Under cool, wet conditions (such as in a potato tuber), B-type starch crystals form, while in warmer, drier conditions (e.g. in a cereal grain), the A allomorph is preferred. Chain length also affects the selection of crystal form, chains of DP <10 do not crystallize, chains with a DP from 10 to 12 tend to form A-type crystals, and chains with a DP >12 tend to yield the B form.37,38 This is likely the result of differences in loss of entropy on crystallization experienced by chains of different lengths.39 An irreversible transition from B-type starch to A-type starch can be accomplished under conditions of low humidity and high temperature. This so-called... 

The interaction of lecithin with starch can also have great functional significance in food systems. Not surprisingly, the structure of the lecithins involved determines their reactivity and hence functionality. Hydrolyzed lecithins have been shown to complex with starch, retarding starch crystallization, and thus slowing staling in yeast-raised baked goods (98, 99). 

The n-alkyl portion of emulsifiers such as glycerol monostearate form a complex with helical regions of starch, a phenomenon that is thought to be responsible for the ability of GMS to retard starch crystallization in bread crumb, slowing the process of staling. Several workers have measured the stoichiometry of complex formation by using various methods. Some of these studies are mentioned later in connection with the discussion on bread staling here three typical reports are summarized. 

Crochet, P. et al., Starch crystal solubihty and starch granule gelatinisation, Carbohydr. Res., 340, 107, 2005. 

Chem. Descrip. Sorbitan laurate CAS 133 39-2 EINECS/ELINCS 215-663-3 Uses Emulsifier lubricant coupling agent softener antistat dispersant emollient water-disp. emulsifier for oils and fats emulsifier in aeams and lotions intermediate may be used to retard starch crystallization in jellies lubricant antistat process aid in PVC resin mfg. food-contact coatings defoamer in fooctonlact paper/paperboard emulsifier in mfg. of... 

Zobel H.F., Starch crystal transformation and their industrial importance, Starch/Stdrke, 40, 1988, 1-7. 

Evidence of starch chemical modification was confirmed by FTIR spectroscopy and X-ray diffraction methods. Compared to starch crystals [68-70], which can be destroyed by using high processing temperature value, CStM is not gelatinized during the processing of the composite film, therefore organic acid modified corn starch can be conveniently used as a filler for plasticized corn starch polymer matrix. 

As observed previously, starch has been largely utilized in blends and nanocomposites with a variety of reinforcements. Less known is the ability to use starch nanocrystals (StNs) as reinforcement in polymer matrices. StNs with dimensions of a few nanometers are formed from acid hydrolysis of starch granules. These starch crystals are mainly formed of crystalline amylose, as acid hydrolysis removes the amorphous domains comprised mostly of amylopectin [172, 173]. Such StN-reinforced nanocomposites were prepared with poly(fS-hydroxyoctanoate) (PHO)... 

Another class of carboxylic acid-derived surfactant is the sodium or calcium salts of fatty acid esters. Commercial examples include metal salts of stearic acid esterified with a dimer of lactic acid (sodium stearoyl lactylate) or maleic anhydride (sodium stearoyl fumarate), which are used as emulsifiers in bread making and in bread preservation due to their properties of preventing starch crystallization and dispersing fats [12, 13]. 

Uses Food emulsifier emulsion stabilizer and film-former in caramels retards starch crystallization in starch jellies inhibits oil separation in peanut butter in dehydrated potatoes antistatfor PP, PS useful in food pkg. 

Uses Food emulsifier inhibits aeration, aids emulsion stability in icings retards starch crystallization in starch jellies provides dryness and overrun in ice cream Reguiatory FDA 21CFR 184.1505... 

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