Beet juice, purification

Limestone-gypsum roasting lithium recovery process, 15 126, 127 Lime water softening methods, 26 116-119 Liming, in beet juice purification, 23 459-462... 

Pregnancy, exposure to organic solvents during, 23 119 Preheater rotary kiln, 25 53 Preheat trains, 23 221-223 Preinstalled piping system, in fine chemical production, 2 2 428-429 Prekallikrein, 4 86-87 Prekallikrein activator (PKA), 22 145, 146 Pre-liming, in beet juice purification, 23 459... 

Knowledge of the chemistry of the raw beet juice is important in controlling the phases of juice purification. The addition of increasing amounts of lime and carbon dioxide should precipitate pectinaceous materials and insoluble anions such as phosphate, sulfate, oxalate, and others, as calcium salts, cause alkaline degradation of invert sugar into lactic and other acids, and flocculation of colorants. Lime is also essential for promoting good fitration. 

Classic juice purification consists of preliming, main liming, first carbonation, first sludge separation (clarification), second carbonation, second sludge separation, sulfitation, and filtration. Control of pH is very important throughout the process and depends on the quality of the beet juice, which is determined in the lab. 

The basic steps in the manufacture of beet sugar (Fig. 6.9) consist of (1) washing, (2) shdng, (3) diffusion, (4) juice purification, (5) evaporation, and (6) crystallization. 

Juice purification. The beet sugar juice is turbid and contains about 17 percent sucrose, 1 to 2 percent organic nonsucrose matter including proteins, aminoacids, amides, saponius, and pectic substances. It also... 

In the initial stages of purification, sucrose is recovered in juice form by crushing cane stalks or by extraction of sliced sugarbeets (cossettes) with hot water. The resulting solutions are clarified with lime, then evaporated to thick syrups from which sugar is recovered by crystallization. The final syrup obtained after exhaustive crystallization of sucrose is known as molasses. Enhanced recovery of sucrose from beet molasses is accomplished by ion-exclusion chromatography, a process used in some sugar mills in the United States, Japan, Finland, and Austria. 

Citrus peel, apple pomace from juice manufacture, and beet pulp left over from the manufacture of sucrose are common commercial sources of pectins. After some preliminary purification of the raw material, the extraction is usually performed with hot dilute acid (pH —1.0-3.5 in a temperalure range of 70-90°Ci. The pectin is then precipitated from the extract with ethanol or isopropanol, or with metal salts (copper or aluminum). The metal ions have to be subsequently removed by washing... 

Juice extracted from cane or beet undergoes further purification steps, including precipitation, absorption, crystallisation and evaporation, which remove nonsugars and progressively concentrate the sucrose solution. The final step is crystallisation of sucrose from the syrup. This mixture of sucrose and liquor, known as the massecuite , is then centrifuged, and the crystals are washed and dried to a moisture content of 0.02% w/w and stored (Beesley, 1990). 

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