Dextrinization conditions

Heating of native dry starch or starch acidified by diluted mineral acids (about 0.2% HCl, H3PO4 or H2SO4), depending on the dextrination conditions (heating at 100-200 °C for several minutes to hours) and type of starch yields three basic types of products ... 

Carbohydrates may be divided into monosaccharides, disaccharides and polysaccharides. The monosaccharides under certain conditions react as polyhydroxy-aldehydes or polyhydroxy-ketones two important representatives are glucose CjHjjO (an aldose) and fructose (laevulose) CgHuO, (a ketose). Upon hydrolysis di- and polysaccharides 3deld ultimately monosaccharides. Common disaccharides are sucrose, lactose and maltose (all of molecular formula C,2H2. 0,), whilst starch, dextrin and cellulose, (CjHjoOj), in which n > 4, are typical polysaccharides. 

Lead azide is not readily dead-pressed, ie, pressed to a point where it can no longer be initiated. However, this condition is somewhat dependent on the output of the mixture used to ignite the lead azide and the degree of confinement of the system. Because lead azide is a nonconductor, it may be mixed with flaked graphite to form a conductive mix for use in low energy electric detonators. A number of different types of lead azide have been prepared to improve its handling characteristics and performance and to decrease sensitivity. In addition to the dextrinated lead azide commonly used in the United States, service lead azide, which contains a minimum of 97% lead azide and no protective colloid, is used in the United Kingdom. Other varieties include colloidal lead azide (3—4 pm), poly(vinyl alcohol)-coated lead azide, and British RE) 1333 and RE) 1343 lead azide which is precipitated in the presence of carboxymethyl cellulose (88—92). 

FIGURE 12.6 Comparison of photodegradation kinetics of bixin in aqueous solutions containing malto-dextrin (MD) under different conditions ( ) microencapsulated and (A) not encapsulated. (From Barbosa, M.I.MJ. et al., Food Res. Int., 38, 989, 2005. With permission.)... 

Commercially, lead azide is usually manufactured by precipitation in the presence of dextrine, which considerably modifies the crystalline nature of the product. The procedure adopted is to add a solution of dextrine to the reaction vessel, often with a proportion of the lead nitrate or lead acetate required in the reaction. The bulk solutions of lead nitrate and of sodium azide are, for safety reasons, usually in vessels on the opposite sides of a blast barrier. They are run into the reaction vessel at a controlled rate, the whole process being conducted remotely under conditions of safety for the operator. When precipitation is complete, the stirring is stopped and the precipitate allowed to settle the mother liquor is then decanted. The precipitate is washed several times with water until pure. The product contains about 95% lead azide and consists of rounded granules composed of small lead azide crystals it is as safe as most initiating explosives and can readily be handled with due care. 

The original initiating explosive used by Nobel and all manufacturers for many years was mercury fulminate. This had the disadvantage of decomposing slowly in hot climates, particularly under moist conditions. For this reason mercury fulminate is no longer widely used. In most countries it has been replaced by a mixture of dextrinated lead azide and lead styphnate. In the U.S.A. some detonators are made containing diazodinitrophenol. 

Nishi et al. [110] used dextran and dextrin as chiral selectors in capillary-zone electrophoresis. Polysaccharides such as dextrins, which are mixtures of linear a-(l,4)-linked D-glucose polymers, and dextrans, which are polymers of D-glucose units linked predominantly by a-(l,6) bonds, have been employed as chiral selectors in the capillary electrophoretic separation of enantiomers. Because these polymers are electrically neutral, the method is applicable to ionic compounds. The enantiomers of basic or cationic drugs such as primaquine were successfully separated under acidic conditions. The effects of molecular mass and polysaccharide concentration on enantioselectivity were investigated. 

Schardinger brought his work on the crystalline dextrins to a close in 1911. He ended his work with the statement I realise that still very many questions remain unsolved. The answer to these I must leave to another, who, owing to more favorable external conditions, can deal with the subject more intensively. It was to be another twenty-five years before the cyclic nature of Schardinger s dextrins was recognized. 

The starch industry has adopted standard conditions for liquefaction. These conditions constitute a short-term jet-cooking treatment of a 35-40% dry solids (DS) starch slurry at 105 C for 5 minutes, known as gelatinization or primary liquefaction, followed by a 90-minute hold at 95 C, known as dextrinization or secondary liquefaction ( ). 

The thermostable CGTase produced by Jhermoanaerobacter sp. ATCC 53,627 is able to liquefy starch at pH 4.5 under standard industrial conditions. It is, therefore, unnecessary to pH adjust the dextrin solution prior to saccharification as is normally done in the industry today. Since there is no need for pH adjustment, significant process advantages are realiz. There is a substantial cost improvement with regard to chemicals, ion-exchange media, charcoal, etc. Also, unwanted by-product formation e.g., maltulose, colored products, base-catalyzed products are reduced. Consequently, these advantages will translate into real savings to the starch industry. 

Nishi has found that chondroitin sulfate A and C are more effective in the resolution of basic drugs than dextran or dextrin and even dextran sulfate because of additional ionic interactions with sulfate or carboxylic groups. The small ionic character of chondroitin sulfate C leads to large enantiose-lectivity under acidic conditions, whereas heparin was not so effective. Using neutral polysaccharides, only hydrophobic interactions and hydrogen bonding may occur (117). 

This study also suggests that molecular size and structure play a role in this interaction. The binding behaviors of dextrin oligomers for four different pharmaceuticals (ibuprofen, ketoprofen, furosemide, and warfarin) were observed under the same experimental conditions. Ibuprofen and ketoprofen, two compounds that are similar in chemical structure and pharmaceutical use, showed obvious differences in interaction patterns (Fig. 13A and B). Ketoprofen, having an extra aromatic ring, required an octa-saccharide (DP = 8) for binding, whereas ibuprofen required a heptasac-... 

Yusuph, M., Tester, R. F., Ansell, R., Snape, C. E. (2003). Composition and properties of starches extracted from tubers of different potato varieties grown under the same environmental conditions. Food Chem., 82,283-289. Zhu, Q., Bertoft, E. (1996). Composition and structural analysis of alpha-dextrins from potato amylopectin. Carbohydr. Res., 288, 155-174. 

Table IV. Changes of the flavor content of cyclo-dextrin spice complexes after ten years storage under nonnal conditions...

No essential difference was found under the experimental conditions between the layer thickness for Newtonian and non-Newtonian liquids, as may be judged from a few data available on non-Newtonian liquids (e.g., latex SKS-30L and dextrin glue). This non-trivial experimental result has not yet been convingly or reasonably explained. 

Determination of the Sugars.—This is carried out by means of Fehling s solution in a portion of the solution of the dextrin in cold water, the ordinary conditions being followed (see chapter on Sugars). 

Measurement of the Viscosity.—This can be carried out either on the solution prepared in the cold or on that prepared in the hot. In the former case, 100 grams of the dextrin are shaken with 500 c.c. of distilled water at 17-5° until the whole of the soluble part has dissolved, the liquid being filtered through a dry filter and the filtrate tested in the Engler viscometer (see Vo I, p. 352). In the second case, the solution is prepared in the hot and the viscosity measured when cold. The value obtained is compared with that given by a standard dextrin under the same conditions. 

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