Amylose solubilization

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

Kim OK, Je JT, Baldwin JW, Kooi S, Pehrsson PE, Buckley LJ (2003) Solubilization of singlewall carbon nanotubes by supramolecular encapsulation of helical amylose. J. Am. Chem. Soc. 125 4426 f427. 

The two major macromolecular components of starch are amylose and amylopec-tin (Figure 5.2). They can be identified only after separation following solubilization... 

Starches with high amylose content, such as corn starch (28% amylose) retrograde more than starches with lower amylose content, such as potato starch (20% amylose). Redispersion of retrograded starch is energy-intensive due to extensive bonding. Temperatures of 115° to 120°C are required to solubilize amylose gels or crystals. Amylopectin gels can be redispersed at temperatures above 55°C. 

It should be noted that the different structures of amylose and amylopectin confer distinctive properties to these polysaccharides (Table II). The linear nature of amylose is responsible for its ability to form complexes with fatty acids, low-molecular-weight alcohols, and iodine these complexes are called clathrates or helical inclusion compounds. This property is the basis for the separation of amylose from amylopectin when starch is solubilized with alkali or with dimethylsulfoxide, amylose can be precipitated by adding 1-butanol and amylopectin remains in solution. 

At pH values close to 7.0 the cowpea protein solubilized and formed the continuous phase in which raw starch granules were dispersed. On heating, the granules absorbed water and as they swelled they exuded some amylose into the continuous matrix prior to the protein denaturation. The higher transition temperature of the protein compared to that of starch created the environment for the leaching of amylose into the solution of the protein (Muhrbeck and Eliasson, 1991). The coexistence of the protein and the amylose in the continuous phase may be responsible for the distinct kinetic pattern in the observed development of G in the cowpea protein-starch blends. For such a system, the protein/starch ratio (R) would reflect the protein/ amylose ratio in the continuous matrix and may be considered to be an important parameter for assessing G of the mixture gels. 

As discussed above, linear alkyl chains such as the fatty acid moiety of monoglycerides can form a complex with helical segments of the solubilized starch molecules. The recrystallization of amylose is apparently little affected by complexation with mono glycerides. Differential scanning calorimetry (DSC) studies of day-old bread crumb show that all the amylose seems to be present in a crystalline state. Complex formation with monoglyceride by the short side chains of amylopectin, however, markedly slow the rate of retrogradation. The half-life for reformation of amylopectin crystals (measured by DSC) is increased twofold to threefold when... 

Amylose Amylopectin Granules Crystallinity Hydrogen bonding Hydrophobic bonding Isolation Fractionation Gelatinization Solubilization... 

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