Acid hydrolysis starch

Enzymes have played an important role in the determination of the structure of starch. Acid hydrolysis of starch provided some controversy about the possible presence of a-1 —> 3, P-1 4, and P-1 6 linkages in starch. This was appar-... 

Ordinary glucose is ct-glucopyranose monohydrate m.p. 80-85°C and [ajp 4-113-4 . In solution it gives a mixture with the form with [alo 4-52-5 . It is manufactured from starch by hydrolysis with mineral acids, purification and crystallization, and is widely used in the confectionery and other food industries. It is about 70% as sweet as sucrose. 

In industrial production of acid-modified starches, a 40% slurry of normal com starch or waxy maize starch is acidified with hydrochloric or sulfuric acid at 25—55°C. Reaction time is controlled by measuring loss of viscosity and may vary from 6 to 24 hs. For product reproducibiUty, it is necessary to strictly control the type of starch, its concentration, the type of acid and its concentration, the temperature, and time of reaction. Viscosity is plotted versus time, and when the desired amount of thinning is attained the mixture is neutralized with soda ash or dilute sodium hydroxide. The acid-modified starch is then filtered and dried. If the starch is washed with a nonaqueous solvent (89), gelling time is reduced, but such drying is seldom used. Acid treatment may be used in conjunction with preparation of starch ethers (90), cationic starches, or cross-linked starches. Acid treatment of 34 different rice starches has been reported (91), as well as acidic hydrolysis of wheat and com starches followed by hydroxypropylation for the purpose of preparing thin-hoiling and nongelling adhesives (92). 

In 1886, Brown11 discovered an organism which formed extremely tough membranes when cultivated m suitable nutrient solutions containing carbohydrates such as D-fructose, D-mannitol or D-glucose ethanol, sucrose or starch did not support membrane formation by this organism which Brown called Bacterium xylinum ) (Acetobacter xylinum). The membranes were readily soluble in cuprammonium hydroxide solution and yielded a dextrorotatory sugar upon acid hydrolysis. These properties and the results of combustion analysis led him to believe that the membrane was cellulose. 

Starch and fatty acids are the main food constituents of biomass. Sugar is derived from starch by hydrolysis or directly by extraction from sugar cane or beet. Fermentation converts sugars into alcohol that can be directly used as fuel, or in principle can be used as the raw material of a bioreftnery plant for further upgrading. Triglycerides, derived from oil seeds, are used to be converted into biodiesel through transesterification processes (Fig. 1.14). 

Wool and Cole (6) described a simulation model based on percolation theory for predicting accessibility of starch in LDPE to microbial attack and acid hydrolysis. This model predicted a percolation threshold at 30% (v/v) starch irrespective of component geometry, but the predicted values are not in accordance with results of enzymatic or microbial attack on these materials (Cole, M.A., unpublished data). Since a model that incorporates component geometry provides a better fit to experimental data than a geometry-independent model does, development of advanced models should be based on material geometry and composition, rather than on composition alone. 

Ccdculated from sulfur anadysis of grafted polymer isolated after removal of starch by acid hydrolysis. 

Eaithfull, N.T. (1990) Acid hydrolysis prior to automatic analysis for starch. Journal of the Science of Food and Agriculture 50, 419-421. 

Putaux, J. -L., Molina-Boisseau, S., Momaur, T., Dufresne, A. (2003). Platelet nanocrystals resulting from the disruption of waxy maize starch granules by acid hydrolysis. Biomacromol, 4,1198-1202. 

Tabata, S., Hizukuri, S. (1971). Studies on starch phosphate. Part 2. Isolation of glucose 3-phosphate and maltose phosphate by acid hydrolysis of potato starch. Starke, 23,267-272. 

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