Acidic hydrolysis of starch

Glucose syrups, also known as com syrups in the United States, are defined by the European Commission (EC) as a refined, concentrated aqueous solution of D(+)-glucose, maltose and other polymers of D-glucose obtained by the controlled partial hydrolysis of starch (Howling, 1984). Glucose syrups were fust manufactured industrially in the nineteenth century by acid hydrolysis of starch. Hydrochloric acid was normally used, because sulphuric acid caused haze in syrups due to insoluble sulphates. The source of starch can vary in the United States corn is widely used, whereas in other parts of the world wheat, potato and cassava starch are also employed. Acid hydrolysis of starch is still used today. The method is non-specific, but if conditions are tightly controlled, it is possible to make products with a reasonably consistent carbohydrate profile. 

The electrolysis of glucose syrup from the acidic hydrolysis of starch yields pure D-glucose. Symp is placed in a chamber with a lead cathode surrounded by diaphragm.321 Starch was similarly electrolyzed, with an energy consumption of 0.05-0.1 kWh/kg of starch. The degradation of starch in alkali is less selective and faster than in acidic medium, as shown in Fig. 38. 

A great advantage that enzymic-catalysis systems have over acid-catalysis methods lies in the much wider range of compositions attainable, as may be seen in the ternary-composition diagram17 depicted in Fig. 4. It illustrates the compositions attainable by (a) the acid hydrolysis of starch and (b) the use of beta-amylase and glucoamylase, or (c) combinations of them. 

Acid hydrolysis of starch is conducted with hydrochloric acid or sulfuric acid, mainly in a continuous process, yielding syrups with 20 to 68 DE. The process consists of the acidification of a starch slurry with hydrochloric acid to a pH of about 1.8 to 1.9, and pumping the suspension into a converter (autoclave) where live steam is gradually admitted to a pressure of 30 to 45 psi. Converted liquids are neutralized with sodium carbonate to a pH of 5 to 7. Proteins, lipids, and colloidal matter are separated as sludge. Pigments are eliminated with activated carbon and minerals with ion exchangers. The raw juice, thus obtained, is evaporated under a vacuum (falling-film evaporator) up to a solids content of 70 to 85 percent. 

Early work on the hydrolysis of starch was reviewed by Rolfe and Defren, who made the first, systematic investigation (following the report by Kirchoffi in 1811 that acid hydrolysis of starch yields a sugarlike sub-... 

Preparation. D-Glucose (often called dextrose commercially, because of its dextrorotation) is manufactured on a large scale by acid hydrolysis of starch, usually potato starch in Europe and com starch in the United States.96... 

G. R. Dean, Acid hydrolysis of starch to D-glucose, Methods Carbohydr. Chem., 4 (1964) 249-250 R. V. MacAllister, Nutritive sweeteners made from starch, Adv. Carbohydr. Chem. Biochem., 36 (1979) 15-56. 

L. Kunlan, X. Lixin, L. Jun, P. Jun, C. Guoying, and X. Zuwei, Salt-assisted acid hydrolysis of starch to D-glucose under microwave irradiation, Carbohydr. Res., 331 (2001) 9-12. 

Mandels et al. (22) found that glucose manufactured commercially by acid hydrolysis of starch contained sophorose as an impurity which is a powerful inducer of cellulase in Trichoderma viride. In the studies... 

The pure oligosaccharides were obtained by preparative liquid chromatography from partially hydrolyzed polymers. Mixture of maltodextrins is a commercial sample obtained by partial enzymic and acid hydrolysis of starch (Roquette, France) Mixture of isomaltodextrins is prepared by partial acid hydrolysis of dextran. Cyclodextrins are commercial samples from Aldrich. 

Such reversion-type reactions are observed, e. g., in the acidic hydrolysis of starch. 

As observed previously, starch has been largely utilized in blends and nanocomposites with a variety of reinforcements. Less known is the ability to use starch nanocrystals (StNs) as reinforcement in polymer matrices. StNs with dimensions of a few nanometers are formed from acid hydrolysis of starch granules. These starch crystals are mainly formed of crystalline amylose, as acid hydrolysis removes the amorphous domains comprised mostly of amylopectin [172, 173]. Such StN-reinforced nanocomposites were prepared with poly(fS-hydroxyoctanoate) (PHO)... 

The acid hydrolysis of starch granules from potato, waxy maize, and amylo-maize-7 was studied in different ratios of mixtures of two of the four alcohols, from 100/0 to 0/100% in 10% (v/v) intervals [53]. Again, a series of soluble limit dextrins was obtained in 48-72 hr of reaction. The average d.p. of the limit dextrins decreased as the content of the higher alcohol was increased. Plots of the d.p. of the limit dextrins vs. the ratio of each alcohol mixture produced curves that resembled titration curves, with different plateau regions in which the d.p. of the limit dextrins changed very slowly or not at all. These plateau regions were characteristic and dependent on the types of alcohols, the volume ratios of the two alcohols in the mixture, and the type of starch. It was proposed that the formation of... 

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-... 

Degradation of starches with malt diastatic enzymes (which contain a-and )S-amylase) depolymerize starch to give soluble starch . "Thin-boiling starches are produced by mild acid hydrolysis of starch. D-Glucose is produced commercially by the total acidic hydrolysis of starch. 

G. is formed as one of the reversion products during the acid - hydrolysis of starch. It is found enriched in the mother liquor - hydrol of dextrose crystallization, together with - isomaltose, - panose and other oligosaccharides. G. cannot be split by a-glucosidases (- amylases) it develops a strong bitter taste. It lowers the crystallization yield of dextrose in starch hydrolysates after acid hydrolysis. 

I. is a-D-glucopyranosyl-l,4-D-glucopyranosyl-1,6-a-D-glucopyranose, which is formed as a component in - branched oligosaccharide syrups by action of transglucosidase (ot-glucosidase) on - maltose. It may also be found as a reversion product of the acid hydrolysis of starch, which is enriched in the mother liquor of glucose crystallization (->hydrol). 

It is obtained from almost complete acid hydrolysis of starch (- hydrolysis, glucosidic linkages), followed by desludging, decoloring, concentration and solidification. The latter is performed either by bulk crystallization and shredding or by spray crystallization. 

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