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Note: all production values in 1031 of dry substance-per year, 1996 values used except where noted. Source: Ref. 2, reproduced with permission. "1995 data.

690 + % of the volume shown is sold within the EU15; less than 10% is sold in other European countries. "1983 data. d1986 data.

'Combined production of 42% db and 55% db fructose-bearing syrups shown.

'Most crystalline (pure) dextrose is monohydrate; some is anhydrous. Main uses are medical in nature. 8At the time of the preparation of this chart, US$1.00 = 8.5 RMB.

'Price for 42% db fructose syrup shown; only one known producer of 55% fructose syrup in the China. 'Combined production data for glucose and maltose syrups. ■'1992 data.

'Totals for the production of these three products in 1992 virtually unchanged from 1986, individual product data not available in 1992 so 1986 values are shown.

'1994 data.

"1991 data.

"1996 list price for 43 DE glucose syrup. "1987 data.

1965 1970 1975 1980 1985 1990 1995 Year

Figure 2. Per capita U.S. sweetener consumption by type. Source: Ref. 1, reproduced with permission.

1965 1970 1975 1980 1985 1990 1995 Year

Figure 2. Per capita U.S. sweetener consumption by type. Source: Ref. 1, reproduced with permission.

state, it occurs in substantial quantities in honey, fruits, and berries. As a polymer of anhydrodextrose units, it occurs in starch, cellulose, and glycogen. Sucrose is a disac-charide of dextrose and fructose. Commercial production of dextrose by hydrolysis of starch yields white crystalline sugars that are either anhydrous (C6H1206) or hydrated by a single water molecule (C6H1206 • H20). Dextrose monohydrate, with its one molecule of water of crystallization per molecule of sugar, separates from concentrated solutions at <50°C (122°F). Anhydrous D-glucose does not contain water of crystallization and separates at 50 to 115°C (122 to 239°F). Another anhydrous form, ^-D-glucose, separates if crystallization is carried out at temperatures >110 to 115°C (230 to 239°F).

In one of the first attempts to prepare commercial dextrose, grapes were used as the starting material (3). It is generally conceded that Kirchoff's work in 1811 was the forerunner of the starch hydrolysate industry (4). It was first reported in 1815 that acid conversion of starch to sugar was the result of hydrolysis of the starch rather than dehydration, and that the starch sugar was identical with grape sugar (5). It was not until 1842, however, that starch hydrolysis was first practiced commercially in the United States. Crystalline dextrose became a main industrial product when a commercially feasible crystallization process was patented in 1923 (6). This patent was one of the rare instances of a crystal structure being the subject of a patent claim. Fifty metric tons of monohydrate dextrose were sold in the United States in 1923. Today, the annual production is more than 500,000 metric tonnes, a 10,000fold increase.

Properties

Physical properties of the three crystalline forms of dextrose are listed in Table 2. In solution, dextrose exists in both the a and /? forms. When a-dextrose dissolves in water, its optical rotation diminishes gradually as a result of mutarotation until, after a prolonged time, an equilibrium value is reached (see arrows, Table 2). At this point, about 62% of the dextrose is present in the fi form. This equilibrium value is not significantly changed over a wide range of temperatures and concentrations. The same equilibrium value apparently exists in anhydrous melts as well as in glassy materials. Pure crystalline yS-dextrose is quite sensitive to moisture, and it changes to the more stable a-form if exposed to high humidity. At 25°C (77°F), a-dextrose monohydrate dissolves fairly rapidly, yielding a solution containing about 30 wt % dextrose. Very slowly thereafter, further quantities of dextrose dissolve until a saturated solution containing ca 50 wt % dextrose is obtained. The first phase of the dissolving process results from the limited solubility of a-dextrose. The slow subsequent dissolution is caused by the transformation of part of the dissolved a-dextrose to the more soluble /? form. When saturation is finally reached, a mixture of a- and ^-dextrose in solution is in equilibrium with solid a-dextrose monohydrate. At 25°C (77°F), anhydrous a-dextrose dissolves rapidly and beyond the limit of solubility of a-dextrose monohydrate. Since the monohydrate is the stable form at

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