Amylopectin fractionation

Specific optical rotation values, [a], for starch pastes range from 180 to 220° (5), but for pure amylose and amylopectin fractions [a] is 200°. The stmcture of amylose has been estabUshed by use of x-ray diffraction and infrared spectroscopy (23). The latter analysis shows that the proposed stmcture (23) is consistent with the proposed ground-state conformation of the monomer D-glucopyranosyl units. Intramolecular bonding in amylose has also been investigated with nuclear magnetic resonance (nmr) spectroscopy (24). 

Starch [9005-84-9] M (162.1)n. Defatted by Soxhlet extraction with Et20 or 95% EtOH. For fractionation of starch into "amylose" and "amylopectin" fractions, see Lansky et al. [J Am Chem Soc 71 4066 1949]. 

Even among nonlinear polymers, many of the materials of interest are composed of a preponderance of bifunctional units with only a minority of polyfunctional units. This applies to vulcanized rubber where no more than about 1 or 2 percent of the isoprene units are cross-linked. It also applies to the amylopectin fraction of starch which consists of chains composed of an average of about 20 glucose units, these chains being connected to one another by trifunctional units to yield an irregular branched array to wool consisting of poly-... 

Especially in the US and European markets, amylases have been added to detergents along with proteases since 1973 to capitalize on the activity of the amylases toward starch-containing soils. From different amylases available, only a-amylases are used for detergents. They are able to catalyze the hydrolysis of the amylose and amylopectin fractions of starch, i.e., cleavage of the a-l,4-glycosidic bonds of the starch chain [15]. This facilitates the removal of starch-based stains by the detergent. 

The differences in the overlap concentrations are instructively demonstrated by Fig. 31 for amylopectin fractions [144], which are representatives for hyper-branched structures. 

Fig. 31. Molar mass dependencies of four differently defined overlap concentrations c (ml/g) for amylopectin fractions in O.Smol/lNaOH [144]. Reprinted with permission from [144]. Copyright [1996] American Society...

Table 5. Values of the parameters and in Eq. (91) for linear and cross-linked polyester chains and for various fractions of amylopectin fractions obtained by a controlled acid hydrolysis [177]...

Yun, S.H. and Matheson, N.K. 1990. Structural changes during development in the amylose and amylopectin fraction separated by precipitation with concanavalin A of starches from maize genotypes. Carbohyd. Res. 270 85-101. 

Starch from ae su kernels in a dent background consists of 51-60% amylose, as determined by the blue value procedure (Table 3.6), with the amylose percentage increasing with increasing kernel age.57 Yeh et al.,90 in contrast, reported that ae su reduced amylose concentration from 65% for su to 28% for ae su, based on SEC separation of starch polysaccharides isolated from kernels in a sweet com background. Three fractions were obtained (Table 3.7). The first two were loosely-branched, similar to the amylopectin fractions in ae. Amylose from the third peak fraction was similar in iodine staining to that from normal however, some short chain length amylose as... 

Parameter Amylose fraction Amylopectin fraction Intermediate fraction... 

Starch is considered to be a neutral molecule, but potato starch has a low degree of phosphation and is thereby endowed with weak polyelec-trolytic character. Starch phosphate esters reside principally in the amylopectin fraction. 

Pullulanase—Converts the amylopectin fraction of starch into linear segments. 

The properties displayed by a starch triacetate, or by other starch esters are dependent upon the type and molecular weight of the starch or starch fraction used for the esterification. The properties may also be influenced by trace constituents or impurities such as compounds of nitrogen and phosphorus which are often observed in starch esters. While the nature of the nitrogenous constituent is not known, it has been demonstrated that much of the phosphorus of potato starch exists as a natural phosphoric ester of the amylopectin fraction. It is not surprising, therefore, that the phosphorus of potato starch is carried through an esterification and may influence the properties of the starch ester. The exact modifying effects of these components on the properties of starch esters, however, are still to be explained. 

Meyer and coworkers have investigated the viscosities of amylose and amylopectin fractions obtained by hot water extraction. Such fractions probably are not pure (see page 261). They have shown that the reduced viscosity, of their corn amylose triacetate in chloroform or in tetrachloroethane varies as a linear function of the concentration, C, whereas the reduced viscosity of corn amylopectin triacetate does not. Amylose triacetate exhibits a considerably higher viscosity than amylopectin triacetate of equal molecular weight. This is probably E. O. Kraemer, Ind, Eng. Chem., 40, 1200 (1038). 

From the mother liquor, the dissolved amylopeclin is recovered by precipitation with ethanol. Combine the precipitate with the sediment obtained by the first centrifugation, to obtain the total amylopectin fraction. 

Apparently, there is no influence of oxygen during the preparation of the fractions in the chloral hydrate procedure, as judged from the values of intrinsic viscosity of the experiments given in Table III. Furthermore, it may be noted that the amylopectin fractions obtained by this method are insoluble in hot water (as well as in cold 1.0 AT potassium hydroxide solution). ... 

From the supernatant liquor, the amylopectin fraction was precipitated by adding sufficient magnesium sulfate to afford a total concentration of salt of 13.0% by wt. Allowing the precipitated amylopectin to remain in contact with the salt solution for 14 hours proved to be sufficient to make it perfectly insoluble in cold water. The amylopectin was then obtained in the dry state by the same technique used for the amylose precipitate. Po-tentiometric titration with iodine at 25.0° and measurement of the intrinsic viscosity at 25.00° were applied in order to characterize both fractions. 

Concentration of magnesium sulfate, % by wt. A mylose fraction Amylopectin fraction Frac- tionation effi- ciency, %... 

The presence of relatively high concentrations of alcohol in the fractionating media has the additional advantage that defatting of the com starch, prior to its fractionation, is unnecessary. It is clear that this process lends itself to continuous operation in a closed cycle, as the aqueous alcohol can, after removal of the amylopectin fraction, be used for dissolving and processing fresh portions of starch. 

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