Dextrins from Potato Starch

Starches like ordinary baking flour and potato starch dextrin work to control insect pests by gumming up the leaf surfaces, trapping and holding the critters until they die. Flour is an old-fashioned pest control, but dextrin is the object of recent attention by researchers looking for new and safe insecticides. Dextrin is actually a sticky sugar extracted from potato starch. 

The first report in the literature of the isolation of a substance recognizable as a cyclodextrin was that of Villiers which appeared in 1891. From digests of Bacillus amylobacter on potato starch, Villiers obtained a small amount (3 g per 1000 g of starch) of a crystalline material, which he named cellulosine because of its resemblance in some respects to cellulose. The foundations of cyclodextrin chemistry were laid down, however, in the period 1903-1911 by Schardinger, and, in fact, some of the older literature frequently refers to the cyclodextrins as Schardinger dextrins. 

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. 

The best dextrins, derived from good potato starch, exhibit a shining reflection, those which appear opaque being usually obtained from wheat or maize starch. 

Starch pastes irradiated with 130,000 V, 15 mA X-rays lost their viscosity, and there was concurrent decrease of iodine-binding ability and pH. Other properties measured after such treatment point to dextrinization and oxidation of starch.78-79 Other results of such irradiation is the cleavage of phosphoric acid esters from glucose units of potato starch. This effect is observed at 50,000 V and 8 mA as well as at 150,000 V and 12 mA. The effect of X-ray irradiation is similar in this respect to irradiation with 7-rays, whereas neither sonication with ultrasound nor exposure to UV light evoke such effects.5 Starch irradiated by X-rays, contains free radicals, and thus the presence of free radicals in starch provides evidence of previous irradiation. 

FIG. 21.—Quantities (Q) [mg/mL] of water-soluble dextrins as a function of water content (W) in potato starch (o, irradiation under oxygen , irradiation under nitrogen) (from Ref. 101). 

Large quantities of starch are consumed as a component of adhesives for paper and paperboard, especially in the production of corrugated board. Dextrins, derived from com or potato starch, are used as adhesives for laminated products and as gums for envelope construction and sealing. 

Potato starch (800 g.) in 9 liters of water containing 2 g. of sodium chloride was hydrolyzed at 20° for twenty weeks with 1 g. of pancreatin (Pharm. Svec. Ed. X) (Table XXV). Apart from small amounts of higher saccharides, tetra- and trisaccharides predominate. The total yield of limit dextrins is high, possibly because the pancreatin contains lower amounts of dextrin-splitting enzymes or because its action ceases at a greater distance from the anomalies. 

Most amylases have only a slight action on the phosphate groups. As mentioned before, the 3-dextrin from potato starch contains all the phosphorus of the starch. This is in accordance with the fact that the phosphorus is concentrated in the amylopectin. A /3-dextrin from arrow-root starch had a phosphorus content of 0.051 % while the starch itself had 0.019%. Since the /3-dextrin corresponds to 40% of the starch, it is evident that here also all the phosphorus is left in the /3-dextrin. 

Dextrin.—Dextrin is a carbohydrate made from starch (chiefly from corn or potato starch) by the application of heat (yellow dextrin) or by treatment with both heat and acids (white dextrin). It forms a paste with water, the yellow variety tending to swell up and dissolve much more readily than the white. When examined microscopically in alcohol mounts, the grains, while conforming in general outline to those of the type of starch from which the dextrin was prepared, nevertheless show more conspicuous striations and clefts.. Corn dextrin shows distinct striations, whereas striations Digitized by Microsoft ... 

Dextrin is prepared by the incomplete hydrolysis of starch by heating in the dry state with or without the aid of suitable acids and buffers moisture may be added during heating. The PhEur 2005 specifies that dextrin is derived from maize (com) or potato starch. A specification for cassava is included in the USPNF 23. 

Dextrinated lead azide, Dextrinated lead azide is made by adding, over a period of 30 min at 60 C. a dilute (3%) sodium azide to an equal volume of a lead acetate solution (7%) which contains dextrin from potato starch in a quantity of 6% to the expected yield of 6% of lead azide. The dextrin solution is made sliglitly alkaline with sodium hydroxide. The product contains ca. 92% of lead azide. 

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