Dextrose, crystallized

When dextrose is heated with methanol containing a small amount of anhydrous hydrogen chloride, a-methyl-D-glucoside is obtained in good yield and can be isolated by crystallization. Similar reactions occur with higher alcohols, but the reaction products are more difficult to isolate by crystallization. Dextrose reacts with acid anhydrides in the presence of basic catalysts, yielding esters. Complete reaction gives the pentaacylated derivative. 

The problem of crystallizing dextrose from starch conversion liquor in a form which would allow separation from the viscous mother liquor was attacked in the latter part of the nineteenth century by various workers. The most successful efforts were made by Behr in 1881.3 Corn starch was hydrolyzed at low concentration, the refined product was concentrated, seeded with a very small proportion of pure anhydrous dextrose crystals, and it was then allowed to stand without agitation in heated rooms. Care was taken to exclude any traces of dextrose hydrate crystals. After several days the crystalline magma was separated and washed in centrifugal filters. By this means individual crystals of anhydrous dextrose of suitable size were obtained and the product... 

Beta dextrose has long been known as a laboratory product obtained by crystallizing dextrose at high temperature in the presence of non-aqueous solvents, particularly glacial acetic acid.17 On a commercial scale, however, these methods are impractical and the operation is performed directly from aqueous solution. 

Although spray-crystallized dextrose-maltose (EMDEX , J. Rettenmaier Sohne GmbH Co. KG, Germany) and compressible sugars are coprocessed, they are commonly considered as single components and are listed as such in the United States Pharmacopeia, while the third edition of the Handbook of Pharmaceutical Excipients has listed SMCC as a separate excipient (58). 

High dextrose equivalent hydrolyzates can be handled so as to crystallize dextrose and remove the impurities as hydrol. In this way dextrose hydrate is produced, having a dextrose equivalent of 99.6+ and 8.5% water of crystallization. This is a white crystalline compound. If suitable conditions are used, crystalline anhydrous dextrose with substantially no water can also be produced. These two types of crystalline sugar are both regular items of commerce. 

All of the products are somewhat hygroscopic, with increasing hygroscopicity as the dextrose equivalent increases, except that crystalline dextrose, separated from its mother liquor, has relatively less hygroscopicity. Thus the higher conversion sirups and the crude sugars are employed as humectants, whereas crystallized dextrose and dried, low conversion sirups are sometimes used as fillers in dry products. 

Dextrose crystallizes with difficulty from water, in which it is very soluble. The crystals contain one molecule of water, and are in the form of microscopic six-sided plates, which grow in masses they melt at 86°. They are.obtained most readily by crystallizing dextrose from 80 per cent alcohol. Anhydrous dextrose is obtained from 95 per cent methyl or ethyl alcohol. In this form the carbohydrate melts at 146°. Pure dextrose is approximately three-fifths as sweet as sugar. It is optically active. 

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