Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
FIGURE 4.3 Beet juice purification.
concentration in thin juice after a second carbonation to a minimum required to
achieve optimum alkalinity. The pH is reduced to 9−9.5.
Normally, fresh and healthy sugar beet contains below 0.1 g invert sugar/100 g
beet. The quantity varies considerably, depending on plant growing condition, maturity,
variety, climate, and conditions and duration of storage. The level of invert
sugar rises during storage of frozen beets because thawing increases the activity of
the enzyme invertase.
Recently proposed have been the application of a slurry activated with lime
milk 5 and the use of flocculants for preliming in order to reduce lime consumption,
possibly down to 0.2−0.3%, a level available in the sugar cane industry.
4.2.4 EVAPORATION
Milk
of lime 0.2—0.3%
Milk
of lime 1.2—1.6%
CO 2
CO 2
Raw juice
Preliming t = 45¡C
Main liming t = 85¡C
1st carbonation
1st filtration
2nd carbonation
2nd filtration
Thin juice to evaporation
Thin juice is warmed to 130−135°C and submitted to evaporators. Multiple-effect
evaporators usually consist of five individual bodies. Such a system allows multiple
use of the same heat energy. It provides a decrease in pressure and temperature when
the juice proceeds through the bodies. The evaporation results in concentration of
dissolved solids in the juice from 12–16% to 60–70%. The juice leaving the last
segment of the evaporator is called thick juice.
The steam boiler in beet sugar production is fired by a variety of fuels such as
coal, natural gas, or oil, and possibly pressed and dried pulp in the future. In the
cane sugar industry, bagasse is used almost exclusively.