For fractionation of starch

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]. 

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. 

Starch can also be modified by fermentation as used in the Rodenburg process. In this case the raw material is a potato waste slurry originating from the food industry. The slurry mainly consists of starch, the rest being proteins, fats and oils, inorganic components and cellulose. The slurry is held in storage silos for about two weeks to allow for stabilisation and partial fermentation. The most important fermentation process that occurs is the conversion of a small fraction of starch to lactic acid by mans of the lactic acid bacteria that are naturally present in the feedstock. The product is subsequently dried to a final water content of 10% and then extruded. 

Starch complexation with thymol was proposed for the fractionation of starch,704 but the procedure is not as efficient as that with 1-butanol. Fractionation with thymol followed by the use of 1-butanol is used to produce high-purity components. Complexation with naphthols revealed that 1-naphthol forms complexes with starch more readily than does its 2-isomer.673 1-Naphthol complexes in two modes, as suggested by the Scatch-ard plot, and the binding is rather weak.717 Complexes between a formalde-hyde-hydroquinone polymer and starch have also been detected.718... 

While specifically developed for fractionating com starch with Pentasol, the following procedure is applicable to any starch and to any of the precipitants indicated above ... 

Starch acetates are the most easUy prepared of the starch esters. They have served frequently for the characterization of starch fractions, for investigations of starch structure and as intermediates - in the preparation of methylated starch. Although most acetylation work has been done on white potato starch, considerable attention has been given to the acetylation of other starches such as those from com, - - - waxy com, wheat, - - - canna, rice, " horse chestnut and banana. ... 

The fractionation of starch has been the subject of many publications in the past as well as in the present. The literature of the last twenty years, especially, shows a rapid accumulation of articles on starch research this can be accounted for by at least three major influences. These are, first, K. H. Meyer s fundamental discovery that most native starches consist, to the extent of about 20 %, of an essentially linear polysaccharide, which he called amylose. Second, T. J. Schoch s equally important demonstration of the ability of amylose to form water-insoluble, complex compounds with minor proportions of higher alcohols. Third, the fast-growing interest which Industry takes in useful polymers. In view of the great successes of cellulose chemistry, amylose chemistry could at least be very promising. 

There can be little doubt that, during most preparative, fractionation methods, a certain amount of degradation is inadvertently introduced. As a result, the intrinsic viscosities of both fractions of starch will be found to be lower than the corresponding values for their native state. In order to make a comparison possible, some method of fractionation has to be developed which gives no degradation whatsoever. In this respect, the techniques outlined in this Section might all have a fair chance of success. Restricting attention to potato starch as a substrate, and furthermore to the intrinsic viscosity of its amylose fraction as measured in 1.0 AT potassium... 

From Fig. 3, it may be seen that lowering of the temperature to 60-70 will cause separation of amylopectin. In general, this phase separation takes the same route as that for the amylose (except for the peculiar, morphological phenomena of the latter). As crystallization is much slower for the branched fraction of starch, the critical temperature of phase separation is sufficiently high to permit the existence of a coherent, liquid phase for short periods of time. The fact that freshly obtained amylopectin precipitate is soluble in cold water, whereas, after several hours, it is completely insoluble in cold water can only be interpreted as being the result of crystallization. In accordance with this conclusion, it is to be noted that this phenomenon is perfectly reversible. 

Whereas all of the methods proposed for large-scale fractionation of starch that have been discussed depend directly on the ability of amylose to form itLsoluble complexes with polar organic compounds. Cantor and Wimmer s process is based on a totally different principle. If a molecularly disperse solution of starch contains a sufficient amount of calcium chloride and caustic alkali is added, a rapid and quantitative precipitation of the starch occurs, because of the formation of complexes (of calcium hydroxide with the starch polysaccharides) which are insoluble in an aqueous, saturated solution of calcium hydroxide. The same phenomenon is observed with the hydroxides of barium and strontium. 

Apart from differences in their solubility, which, in a sense, might be regarded as secondary differences, the fractions obtained by the several industrial methods also show primary differences with regard to their iodine values and intrinsic viscosities. In Table IX, the (smoothed) averaged values of these fundamental properties have been listed for fractionation of potato starch according to the several industrial methods discussed. 

Although, for obvious reasons, fractional precipitation from salt solutions is by far the most economical of the methods discus.sed for the industrial fractionation of starch, such processes as that of Cantor and WimmeH might possibly become of interest for the production of reactive intermediates of each starch fraction. Several types of chemical derivatives of both starch components can be synthesized by way of the calcium hydroxide complexes. 

A product made from renewable raw materials has also been active in this application. Oxidation of the amy-lopectin fraction of starch with periodic acid cleaves some vicinal diol structures to dialdehydes which can be oxidized further to dicarboxylic acids.273 For good activity... 

Retrogradation rate strongly depends on water content (Figure 6.27b), and the relation is similar to that with temperature. According to Eq. (6.14), the supersaturation will be greater for a higher volume fraction of starch. On the other hand, at very low water content the mobility of the polymer chains will be very small, which will reduce the rate at which crystallites are formed. For 20% water at room temperature the mobility is effectively zero and no retrogradation occurs. 

Since starch is a polymeric glucoside composed of a-1,4- and a-1,6-linked glucopyranosidic units, it was of interest to examine the thermal properties of the linear polymeric fraction of starch, namely, that of amylose. The DTA curves for various amylose fractions, prepared from the same starches, have been reported. Examination of the three fractions reveals three distinct features the endothermic peaks with A7 in of about 150 and 225°C, and a shoulder peak with a A7 in of 3l5°C. There were pronounced exothermic peaks in the 490-51O C temperature range. 

First described in the literature in 1814, the blue reaction of iodine with starch is the best-known example of a polymerization process induced by supramolecular stabilization. Structural studies indicate that amylose (the linear fraction of starch) forms a helix with six glucose residues per turn to include guest iodine molecules. Inside this helix, iodine molecules form a polymeric chain with a periodicity of 3.1 A, which is much shorter than the nonbonded distance between iodine atoms (4.3 A) but greater than the single I-I bond distance (2.7 A). The amylose-iodine reaction is widely used in analytical chemistry and was utilized for the solubilization and purification of carbon nanotubes. 

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