Dextrinization of starch

Instant soup Dextrinization of starch granules Viseosity... 

As shown by the present authors, atmospheric oxygen does not affect DTA, DTG, and TG curves to such an extent that oxidation can be accepted as an important process in the range up to 300°. The dextrinization of starch does not change the points of thermal effects, that is, an endothermic effect, with its maximum at —80° (loss of humidity), a very small endothermic effect between 200 and 222°, which ceases at the stage of fully soluble... 

A different chemistry must be involved in the formation of pyrodextrins, that is, the dextrinization of starch in the presence of catalysts. TTie methylation analysis of various pyrodextrins " indicated this well (see Tables... 

Sucrase-isomaltase complex An enzyme complex comprised of two enzyme units. Both units have high a-l,4-glucosidase activity and will hydrolyze maltose and maltotriose to glucose. The sucrase unit will also hydrolyze sucrose to fructose and glucose, whereas the isomaltase unit will hydrolyze a-1,6 bonds found in isomaltose and the limit dextrins of starch. 

Figure 6.8 Hydrolysis and repolymeiization during dextrination of starch. (From Jarowenko, N., Harjdbook of...

Quantitatively, the breakdown of starch to dextrin [9004-53-9] and maltose [69-79 ] is by far the most important. It takes place according to the following equations. 

Note. The cyclic oligosaccharides arising from enzymic transglycosylation of starch have been referred to as Schardinger dextrins. These names (and those of the cyclohexaamylose type) are not recommended, but the abbreviation CD is tolerated. 

The hydrolysis of starch by salivary and pancreatic amylases catalyze random hydrolysis of a(l—>4) glycoside bonds, yielding dextrins, then a mixmre of glucose, maltose, and isomaltose (from the branch points in amylopectin). 

Cellulose is a high molecular weight polymer of D-glucose with fi( 1 -4)-glycosidic bonds, found in plant fibres it is the major component of most plant tissues. Starch is another common polysaccharide, containing two polymers of glucose, amylose and amylopectin. It was used in some paint preparations and in the production of paper. Acid treatment of starch produces dextrins, which are used as adhesives and additives in water colour paintings. 

A second method that is frequently used to measure the dextrinogenic activity of alpha amylases is based upon the hydrolysis of starch to dextrins of low molecular weight which give a red or a colorless solution with iodine. 

Upon extensive hydrolysis of starch by either of these enzymes, only small differences were observed in the concentrations of the products or in the average degrees of polymerization of the dextrins. These comparisons were made for equivalent stages of hydrolyses and are not necessarily related to the rates of the hydrolysis of starch by these two amylases. 

Studies of the rate of the hydrolysis of dextrins isolated from a reaction mixture after the extensive hydrolysis of starch by maltase-free malted barley alpha amylase, led Myrback11 to conclude that the flattening of the reaction curves with this amylase is not due to equilibrium between the amylase and the products of the hydrolysis. As indicated above, similar conclusions have been reached for pancreatic amylase and for the amylase of Aspergillus oryzae.41,7a... 

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