Hydrolysis of carbohydrate

The inversion of sucrose can be effected in the presence of strongly ion-exchange 

The reaction is first order with respect to sucrose concentration for temperatures between 323 and 348 K. The rate is strongly influenced by intraparticle diffusion, with no indication that the external mass transfer is significant. 

The hydrolysis of lactose in a continuous fixed-bed column reactor containing strongly acidic resins was reported by Chem and Zall. The reaction was first order and the activation energy was 154 kj mol . At 368 K, 99% of the lactose in the whey was hydrolyzed within 3 h of residence time when the substrate was acidified with concentrated nitric acid to a final acid concentration of 0.6 mole 1 .  

Hydrolysis of disaccharides — cellobiose, maltose and lactose — was investigated over A, X, and Y type zeolites. The conversion profiles of the hydrolysis of cellobiose over NaX are shown in Fig. 4.19. The reaction was carried out at 373 K and initial reactant concentration of 1.0 wt%, and a catalyst loading of 0.1 gcm . Total conversion is based on the amount of cellobiose consumed by the reaction. A very large fraction of the reaction occurs within the first 0.5 h and the entire reaction terminates after 1 h. The pH profile of the reaction broth is also shown in Fig. 4.19. Upon addition 

The time courses of hydrolysis of maltose over NaX and of lactose over NaA at 358 K are shown in Figs. 4.20 and 4.21, respectively. 

One of the most common hydrolysis reactions is that required to convert polysaccharides into monosaccharides prior to the determination of total carbohydrates in food and environmental samples. The use of highly acid media (e.g. 12 M sulphuric acid) and elevated temperatures ( 100°C) for 20 min produced partial oxidation of carbohydrates [80]. Using room temperature to avoid oxidation resulted in incomplete hydrolysis [81], and so did lowering the concentration of sulphuric acid to 0.5 M while keeping the temperature at 100°C for 8 h [82-84]. One of the most accurate ways of determining total carbohydrates is by using 1 M HCI at 100°C for 20 h [85,86]. 

Existing studies on the US-assisted hydrolysis of carbohydrates have failed to clarify the behaviour of chemical systems upon US irradiation [87]. Thus, Dubois et al. used a US bath at a frequency of 35 kHz — further details were not reported — as, in their opinion, a probe increases the temperature of the irradiated system significantly. They found very acid conditions (12 M sulphuric acid) to cause total degradation of carbohydrates — the sonicated solution did not exhibit any absorption at 485 nm after the addition of phenol for the development of the Dubois method [88]. They concluded that promoting hydrolysis in an acid medium — it is unclear whether they assayed different acid concentrations — is not feasible and performed the ultrasonicated hydrolysis step in pure water for 3 h, after which they added the acid to develop the derivatizing reaction. Further research on this topic is clearly required in order to clarify such an uncommon behaviour. 

The above examples clearly show that the experience on hydrolysis largely acquired in dealing with organic compounds for non-analytical purposes [1-7] has been underexploited in the analytical field. 

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Cellobiose was prepared first by Skraup and Konig by the saponification of the octaacetate with alcoholic potassium hydroxide, and the method was improved by Pringsheim and Merkatz.3 Aqueous barium hydroxide also has been employed for the purpose, and methyl alcoholic ammonia has been used extensively for the hydrolysis of carbohydrate acetates. The method of catalytic hydrolysis with a small quantity of sodium methylate was introduced by Zemplen,i who considered the action to be due to the addition of the reagent to the ester-carbonyl groups of the sugar acetate and the decomposition of the addition compound by reaction with alcohol. The present procedure, reported by Zemplen, Gerecs, and Hadacsy, is a considerable improvement over the original method (see Note 2). 

The absorption efficiency of the different carotenoids is variable. For example, (3-cryptoxanthin has been reported to have higher absorption efficiency than a-cryptoxanthin in rats (Breithaupt and others 2007). Carotenoids must be liberated from the food before they can be absorbed by intestinal cells (Faulks and Southon 2005). Mechanical disruption of the food by mastication, ingestion, and mixing leads to carotenoid liberation (Guyton and Hall 2001). The enzymatic and acid-mediated hydrolysis of carbohydrates, lipids, and proteins (chemical breaking of the food) also contributes to carotenoids liberation from the food matrix (Faulks and Southon 2005). Once released, carotenoids must be dissolved in oil droplets, which are emulsified with the aqueous components of the chyme. When these oil droplets are mixed with bile in the small intestine, their size is reduced, facilitating the hydrolytic processing of lipids by the pancreatic enzymes (Pasquier and others 1996 Furr and Clark 1997 ... 

Figure 3.19 The hydrolysis of carbohydrate during acid pulping.

The design of solid catalysts for the hydrolysis of carbohydrates is now considered as one of the most challenging topics since this reaction opens a direct access to different chemicals [8, 13] of increasing value [14-20]. 

Scheme 2 Hydrolysis of carbohydrates over cation-exchange resins...

Heterogeneously-catalyzed hydrolysis of carbohydrates is governed by several parameters. The most important of them is the accessibility of the catalytic sites and the stabihty of solid catalysts in water. 

Friedman, M., McDonald, G. M. (1995). Acid-catalyzed partial hydrolysis of carbohydrate groups of the potato glycoalkaloid a-chaconine in alcoholic solutions. J. Agric. Food Chem., 43, 1501-1506. 

Bertino, D. J., P. W. Albro, and J. R. Hass. 1987. Enzymatic hydrolysis of carbohydrates in aquatic fulvic acid. Environmental Science Technology 21 859-863. 

Conversion of lignocellulosic material to ethanol requires hydrolysis of carbohydrate polymers to their constituent sugars. Enzymatic hydrolysis is a common approach to hydrolysis and offers the benefits of mild... 

Furosemide can also be synthesized starting with 2,4-dichlorobenzoic acid (formed by chlorination and oxidation of toluene). Reaction with chlorosulfonic acid is an electrophilic aromatic substitution via the species -S02C1 attacking ortho and para to the chlorines and meta to the carboxy-late. Ammonolysis to the sulfonamide is followed by nucleophilic aromatic substitution of the less hindered chlorine by furfurylamine (obtained from furfural—a product obtained by the hydrolysis of carbohydrates). 

Column separations of the products of hydrolysis of carbohydrate boronates by use of anionic resins provides an alternative, efficient means of deboronation,27,67 69 and other similar separations have used columns of cellulose,48 alumina,67 and, for carbonyl-containing compounds, anion-exchange resins in the hydrogensulfite form.53 In special cases, electrophoresis30 and direct crystallization23 have been employed. 

A mouth for biting off and chewing food and for admixing saliva containing enzymes to initiate hydrolysis of carbohydrates and fats. 

Regarding the detailed mechanism of the acid-catalyzed hydrolysis of carbohydrate orthoesters in general, the reaction may probably best... 

Application of this simple and clear concept to the acid hydrolysis of carbohydrate orthoesters leads to a reaction sequence initiated by the coordination of the first proton to the most strongly basic" dicovalent oxygen atom (first step). 

Identified products of acid hydrolysis of carbohydrate residue D-glucosamine D-glucosamine, hexose... 

Carbohydrate SXA, on acidic hydrolysis, yields galactose, galactose phosphate, galactosamine, ribitol, anhydroribitol, ribitol phosphates, and inorganic phosphate. Alkaline hydrolysis of carbohydrate SXA, followed by enzymic dephosphorylation and separation of the product... 

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