Food Chemistry

872 19 Sugars, Sugar Alcohols and Honey

and 1−2% of water. It is light yellow to dark

brown in color due to the adhering syrup. Like

the after-product sugar (3−4% of organic and

1. 5 − 2 .5% of inorganic nonsugar substances

and 2−3% of water) obtained in the last

crystallization stage, raw sugar is generally

not suitable for direct use. It is processed to

consumer sugar in refineries.

In the refinery, the sugar is mashed into

a magma with a suitable syrup, centrifuged,

and washed with water and steam (affination).

Thus, it directly yields a consumer sugar

called affinated sugar. Another possibility is

to dissolve the sugar and feed the resulting

syrup (liquor) to a crystallization process

which then yields refined sugar, a consumer

sugar of the highest quality.

A simplified crystallization scheme for the

production of white sugar is presented in

Fig. 19.8. After affination and dissolving, the

raw sugar and after-product sugar accumu-

lating in the course of the process are boiled

down together with the thick syrup, and the

Fig. 19.8.White sugar evaporation and crystallization.
Quotient Q: % saccharose in dry matter

Table 19.6.Production lossesaduring saccharose re-

covery from sugar beet

Processing step 1950 1974

Beet slice extraction 0. 4 − 0. 50. 15 − 0. 25

Sugar extract purification 0. 1 − 0. 20. 02 − 0. 05

Other steps 0. 6 − 0. 80. 25 − 0. 90

Total process 1. 1 − 1. 50. 42 − 0. 60

aSugar amount in % based on the processed beet

weight.

main part of the sugar finally crystallizes out

of the supersaturated solution as white sugar.

Centrifugation at 40–45◦C yields not only

crystals of 2−4 mm (first-product sugar), but

also centrifugal syrup (green syrup) which

is subjected to two further crystallization

steps. The last discharge, a highly viscous

brown syrup, is molasses. In the processing

of thick syrup to refined sugar, first raw sugar

is isolated exclusively. It is then dissolved

and fed back into the crystallization process.

In this way, the process is independent of

variations in the quality of the thick syrup.

Processing losses in sucrose recovery from beets

in 1974 were 0. 4 − 0 .9% (sugar determined polari-

metrically; and based on processed beet weight)

and, when compared to 1950, represent a sig-

nificant improvement of the sucrose yield (Ta-

ble 19.6). This technological progress is also re-

flected in a rise of work productivity (work min/t

beets), which was 130−150 in 1950 but only

12 −30 in 1974.

19.1.4.1.3 Production of Cane Sugar

Sugar cane processing starts with squeezing out

the sweet sap from thoroughly washed cane.

For this purpose, the cane moves to a shredding

machine where knives shred the stalks and then

moves to crushing machines where a series of

revolving heavy steel rollers squeeze the cane

under high pressure. After the first roller, more

than 60% of the cane weight is removed in the

form of sap which contains 70% or more of

the cane sucrose content. Repeated squeezing

provides a sucrose yield of 93–97.5%. The

squeezing may be combined with extraction by

mixing the “bagasse” (the pressed cane) with hot