Starch amylopectin from

In a current rheological study [296], the galactoxyloglucan from Hymenia courbaril was mixed with starch containing 66% amylose and with waxy corn starch (amylopectin). The gel mixtures showed, under static rheological conditions, an increase in paste viscosity compared to those of the polysaccharides alone. Dynamic rheometry indicated that the interactions resulted in increased thermal stability of the gel formed in comparison to that of the starch alone. 

Table I shows the results of periodate oxidation and methylation applied to amylopectins from various sources. If the percentage of amylose in a whole starch is known, the length of unit chain of the amylopectin component can be calculated from the results of periodate oxidation of the whole starch (see Table II). The length of unit chain appears to depend on the botanical species, but not the variety, from which the starch wras isolated. In the case of tapioca and corn amylopectins, sub-fractionation of these by precipitation with methanol, followed by periodate oxidation, showed the sub-fractions had the same degree of branching as the original amylopectins.71 The action of periodate on whole starches and amylopectins is now so well established and accurate, that it may well completely supersede the methylation technique for pure starches, in view of its many advantages.

Starch source Amylose, % Average (a) by metky-lation length of t b) by Periodate oxidation tnit chain (c) calc, for amylopectin from (6) References... 

The variation between the starch from different plants is considerable. The percentage of amylose varies from 27% in maize starch through 22% in potato starch to 17% in tapioca starch. The waxy maizes are unusual in that they are almost pure amylopectin. This is extremely convenient because it avoids the need to separate amylopectin from amylose chemically. 

Yusuph, M., Tester, R. F., Ansell, R., Snape, C. E. (2003). Composition and properties of starches extracted from tubers of different potato varieties grown under the same environmental conditions. Food Chem., 82,283-289. Zhu, Q., Bertoft, E. (1996). Composition and structural analysis of alpha-dextrins from potato amylopectin. Carbohydr. Res., 288, 155-174. 

Fredriksson, H., Bjork, L, Andersson, R., Liljeberg, H., Silverio, J., Eliasson, A. -C., Aman, P. (2000). Studies on a-amylase degradation of retrograded starch gels from waxy maize and high-amylopectin potato. Carbohydrate Polymers, 43, 81-87. 

Table 10.7 Molecular pi 104,111,210 commerce roperties of amylopectins from wheat and other starches of ...

Shibanuma et al.232 examined the molecular structures of starch isolated from three Japanese wheat varieties, one Australian standard white wheat and one US western white wheat. The data presented in Tables 10.9 and 10.10 again indicate that the properties and structural features of amylose and amylopectin are dependent on the starch source. The molecular sizes of amylose and amylopectin were larger in the US wheat compared to the corresponding starch fractions from the Australian and Japanese wheat starches. Among the five wheats, the two preferred for salt noodles in Japan, the Japanese variety Chihoku and the Australian standard white, contained a higher proportion of branched amylose and a lower number of chains per amylose... 

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