Starch, enzyme hydrolysis

Pacsu4 5 has suggested a structure for starch involving a small number of non-cyclic hemiacetal linkages, the number being presumably sufficient to account for the number of endgroups determined by the methylation method. Halsall, Hirst and Jones6 have commented on this structure, however, and have shown it to be incompatible with the results of periodate-oxidation studies. In addition, these authors pointed out that it would be difficult to explain enzymic hydrolysis and dextrin formation on the basis of such a structure. 

Products.—Considerable information concerning the mechanism of the enzymic hydrolysis of starch has been obtained from investigations of the action of purified maltase-free pancreatic amylase on a number of different substrates. The substrates studied were ordinary unfractionated but exhaustively defatted10 potato and com starches a branched chain substrate, waxy maize starch and amylose, the linear component of corn starch.41 69 eo f4 These investigations included comparisons not only of the rates of the hydrolysis of the different substrates but also of the products formed from them. 

Srichuwong, S., Isono, N., Mishima, T., Hisamatsu, M. (2005). Structure of linterized starch is related to X-ray diffraction pattern and susceptibility to acid and enzyme hydrolysis of starch granules. Int. J. Biol Macromol, 57,115-121. 

Potato starch usually contains 0.01-0.6% (w/w) phosphorus. Although phosphorus is present at very low levels, it has a significant effect on the physicochemical properties of starch. Phosphorus is in part responsible for the high swelling power, paste stability, and resistance to enzyme hydrolysis of potato starch. Potato starches contain significant amounts of monophosphate esters... 

The investigations carried out by Professor French and his students were based on sound experimental approaches and on intuitive theoretical considerations. The latter often resulted in new experiments for testing a hypothesis. On the basis of theoretical considerations, Professor French proposed a model for the structure of the amylopectin molecule, and the distribution of the linear chains in this molecule. This model was tested by utilizing enzymes that selectively cleave the linear chains, and the results substantiated the theoretical deductions. He proposed a theory on the nature and types of reactions occurring in the formation of the enzyme - starch complex during the hydrolysis of starch by amylases. In this theory, the idea of multiple attack per single encounter of enzyme with substrate was advanced. The theory has been supported by results from several types of experiments on the hydrolysis of starch with human salivary and porcine pancreatic amylases. The rates of formation of products, and the nature of the products of the action of amylase on starch, were determined at reaction conditions of unfavorable pH, elevated temperatures, and increased viscosity. The nature of the products was found to be dramatically affected by the conditions utilized for the enzymic hydrolysis, and could be accounted for by the theory of the multiple attack per single encounter of substrate and enzyme. 

Resistant starch escapes hydrolysis by starch-specific enzymes (see Commentary). Studies have shown that resistant starch, upon treatment with DMSO, becomes solubilized and, thus, hydrolyzable by amylase enzymes. 

Presence of native starch crystals. In plant materials, starch exists as semicrystalline, granular entities. Starch molecules, both amy-lose and amy lopectin, with their many intermo-lecular hydrogen bonds, give structure to the starch granule (Zobel, 1988). The crystalline regions formed by this intermolecular hydrogen bonding are somewhat resistant to enzyme hydrolysis and need to be broken prior to enzyme treatments. 

Glucose syrups. Glucose syrups are a group of industrial syrups manufactured from starch - usually corn starch (maize). The starch may be hydrolysed by either acid or enzymic hydrolysis or, more usually, a combination... 

Converted starches, also called thin-boiling starches, are produced by degradation of the starch chains into small segments. They can be cooked in water at higher concentrations than native starches. Low-viscosity starches are needed in applications where a high solid starch paste with a pumpable and workable viscosity is required. There are four classes of commercial converted starches dextrins (hydrolysis in solid-state) acid-modified starches (hydrolysis in a slurry) oxidized starches and enzymically depolymerized starches. 

This review has shown that most studies on barley starches have been focused on understanding the fine structures, particle size distribution, chemical composition, gelatinization properties and susceptibility towards enzyme hydrolysis. However, there is a dearth of information on the rheological and retrogradation characteristics of barley starches from different cultivars. Furthermore, the response of small and large barley starch granules towards physical and chemical modification needs investigation. Research in the above areas is underway in our laboratories. It is hoped that this study may improve the utilization of different types of barley starches for specific products within the food and paper industry. 

Hydrolysis of starch (enzyme versus acid catalysis)... 

Zittan, L., Enzymic hydrolysis of inulin an alternative way to fructose production, Starch/Starke, 33, 373-377, 1981. 

The general mode of action of detergent enzymes is quite similar. Detergent enzymes usually belong to the class of so-called hydrolases. These enzymes are able to split polymeric structures of stubborn soils such as proteins (e.g. blood, egg or starch) by hydrolysis and the fragments of the polymeric structures have to be subsequently detached by the surfactant system. 

The com industry makes widespread use of enzymes for carbohydrate conversion. The advent of enzyme technology in the corn industry in the 1960s dramatically changed the starch industry and allowed the development of new products. Today, enzyme hydrolysis of starch has largely replaced acid hydrolysis, which is used as an adjunct in starch conversion. Enzymes used to make corn syrups and HFCS include the following. 

S. Peat, J. R. Turvey, and J. M. Evans, The structure of floridean starch. Part II. Enzymic hydrolysis and other studies,./. Chem. Soc. (1959) 3341-3344. 

Fig. 28.—The variation of the iodine binding capacity of starch in the course of the enzymic hydrolysis of starch and the starch-iodine complex. (Reprinted with permission from J. Hollo and J. Szejtli, Brauwissenschaft, 13 (1960) 380-386.)...

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