All-amylopectin potato

Although cationic com, tapioca, wheat and potato starches are the most common commercial products, preparations, properties and performance of cationic oat31 and pea32 starches have been reported. Improved retention performance via the use of a blend of cationic cereal (wheat, com) starch and cationic potato starch has been reported.33 Products for papermaking using all-amylopectin potato starch have been proposed.34-39... 

The past two decades have also seen a considerable enlargement and maturation of the cassava (tapioca) starch industry that is reflected in another larger chapter, which also compares the characteristics of tapioca/cassava starch with those of other starches. The chapter on potato starch has also been considerably updated, especially from a processing standpoint. The latter chapter contains a discussion of all-amylopectin potato starch. 

Tapioca and maize amylopectins have been sub-fractionated by fractional precipitation from aqueous solution with increasing amounts of methanol,64 71 and potato amylopectin by preferential precipitation on electrodialysis of the iodine complex.72 When these three amylopectins were subjected to chromatography, and eluted with a neutral buffer, all were found to consist of several sub-fractions.70... 

Maltose (3-amylases are primarily found in plants and have been isolated from sweet potatoes,27 soybeans,28 barley29 and wheat.30 Maltose (3-amylases are also elaborated by bacteria, e.g. by Bacillus polymyxa,31 B. megaterium,32 B. cereus33 and Pseudomonas sp. BQ6.34 These (3-amylases all produce (3-maltose and a high molecular weight (3-limit dextrin. The limit dextrins result when the enzyme reaches an a-(l—>-6) branch linkage, which it cannot pass. Approximately half of an amylopectin molecule is converted to (3-maltose the remaining half is the (3-limit dextrin. 

Amyloses of five commercially important starches (wheat, corn, rice, tapioca and potato) were purified by fractional crystallization of their amylose-alcohol complexes and shown to be free of amylopectin.111,205 All five amyloses showed comparable iodine affinity, blue value and max of their polyiodide complexes (Table 10.5), which is consistent with their being (1 —4)-linked a-glucans with an average DPn of —500 or above.206 The average size of amylose molecules in cereal starches is smaller than... 

Most amylases have only a slight action on the phosphate groups. As mentioned before, the 3-dextrin from potato starch contains all the phosphorus of the starch. This is in accordance with the fact that the phosphorus is concentrated in the amylopectin. A /3-dextrin from arrow-root starch had a phosphorus content of 0.051 % while the starch itself had 0.019%. Since the /3-dextrin corresponds to 40% of the starch, it is evident that here also all the phosphorus is left in the /3-dextrin. 

Staudinger and Husemann determined the osmotic pressure of solutions of a potato starch acetate which had been fractionated into four parts by precipitation of its chloroform solution with ether. The molecular weights of the fractions ranged from 45,000 to 275,000. All of the fractions were soluble in chloroform, but fractions of low molecular weight were also soluble in acetone. For various concentrations of solute in either chloroform or acetone, the osmotic pressure did not increase in direct proportion to the solute concentration, but the deviation from van t Hoff s law was the smallest in the case of the acetone solutions. Osmotic pressure measurements on amylose and amylopectin tri-acetates dissolved in tetrachloroethane have been made by Meyer and co-workers, who have deduced molecular weights for these substances of approximately 78,000 and 300,000, respectively (see above discussion of the purity of these fractions). 

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