By-Products of the Sugar Industry

The sugar industry produces many by-products along with sugar. These include molasses, bagasse, beet pulp, alcohol, pulp for paper industry, press-mud fertilizer, and a power source from burning bagasse. 

Molasses. Molasses is the final effluent obtained in the preparation of sugar by repeated crystallization. The sugar it contains cannot be removed economically. The molasses from cane sugar is most commonly known as blackstrap and that from beet is called beet molasses. Molasses is mainly used for the manufacture of ethyl alcohol (ethanol), yeast, and cattle feed. Another use of sweet molasses is in cooking, spreads for bread, topping for pancakes, and in the manufacture of alcoholic beverages. 

Bagasse and beet pulp. Bagasse is a fibrous residue of the cane stalk that is obtained after crushing and extraction of juice. It consists of water, fiber, and relatively small quantities of soluble solids. Bagasse is usually used as fuel in the furnaces to produce steam in sugar factories. It is also used as a raw material for production of paper and as feedstock for cattle. 

The pulp, leaving the diffuser after the extraction of sugar from the beet cossettes, is pressed in screw-t5q e presses to remove water. The pressed pulp is enriched by the addition of molasses or concentrated Steffen filtrate and is dried in rotary driers. Molasses-dried beet pulp 

The material removed from the filters during clarification of the juice contains the settled insoluble solids. The mud is returned to the fields as fertilizer. Some sugar factories extract a crude wax from the filtered mud, which is used in the manufacture of polishes. 

---

Enzymes can be used to specifically modify the pectins. Pectin methyl esterase is already widely used to adjust the gelling properties of commercially available pectins. The acetyl esters also strongly affect the gelation [2,3] and removal is important for the upgrading of sugar beet pectin, extractable from a by-product of the sugar industry. 

Sugar cane wax is an interesting by-product of the sugar industry and one which has for the most part been neglected. It occurs in the so-called factory mud, which is usually discarded. It has been shown, however, that extraction of the wax is possible and that the product can be resolved into a fatty substance and a wax proper. The mud is extracted with benzene and the crude wax resolved into a pure wax and a fatty portion which is soluble in cold acetone. Indian workers have preferred to use an initial extraction with petroleum ether and to purify the extract by treatment with nitric acid. Alternatively the wax may be extracted directly from the expressed juice before the latter is processed for sucrose manufacture. The wax is of good quality approaching that... 

Waxes are of considerable commercial importance, as synthetic materials have not been produced at a price that will allow them to compete with the natural substances. The most important natural waxes are camauba from palms of the genus Copernicia, candelilla from Euphorbia antisyphlitica, and sugar cane wax—a by-product of the sugar industry (Schery, 1972). 

On treatment with a non-enolizable aldehyde and sodium hydride, rruns-related a-hydroxyepoxides were converted to acetals. The reaction is thought to proceed by way of a hemiacetal salt, as illustrated in Scheme 2. L-Galactono-1,4-lactone, a by-product of the sugar industry, furnished a diastereomeric mixture of 5,6-alkylidene acetals 18 in >60% yield on microwave irradiation in the presence of long-chain aldehydes and montmorillonite KSF as catalyst, and 4,6-O-alkylidene derivatives 19 of D-glucose have been prepared by use of long-chain aldehydes and catalytic pyridinium />-toluenesulfonate in benzene under azeotropic removal of water. Compounds 18 and 19 were of interest in liquid crystal studies. 

Lactose (Milk Sugar), C HjjOii.HjO mw 360.31, monoclinic spheroidal crysts (from w), pip 201—202° (becomes anhydr at 120°), bp (dec), d 1.53g/cc at 20°. Present in the milk of mammals, and is produced commercially from whey, a by-product of the cheese industry. 

Acetals of L-galactono-1,4-lactone (an abundant by-product of the sugar beet industry) have thermotropic liquid crystalline properties. Acetalization in DMF containing H2SO4 in the presence of anhydrous CUSO4 gave (after 12 to 24 h at 40 °C) yields of 20-35% (Scheme 10.89) [173]. 

Because of their interest in products with liquid crystalline and surfactant properties, Csiba et al. [15] synthesized some amphiphilic derivatives of L-galactono-1,4-lactone 24, a by-product of the sugar beet industry available in large quantities. Reactions between 24 and hexyl, heptyl, octyl, decyl, dodecyl, and myristyl aldehydes on montmorillonite KSF or KIO were performed in a focused open-vessel micro-wave system for 10 min in the absence of solvent (Scheme 12.10). Protected derivatives 25a-f were afforded with yields (60-89%) considerably better than those (22-38%) obtained by conventional heating for 24 h in the presence of sulfuric acid. 

Levan. Like dextran, microbial levan is often an undesirable by-product in the sugar industry. It was first reported by Lippmann in 1881 as a product which increases the viscosity of the processing sugar liquor.In 1901, Greig-Smith found that a strain of Bacillus grown on sucrose produces a fructose polymer which was named levan by analogy to dextran. ... 

Molasses, which is a by-product of the sugar beet and sugarcane industries (see p. 536), was one of the earhest silage additives to be used as a source of sugars. The by-product has a water-soluble carbohydrate content of about 700 g/kg DM the additive has been shown to increase the dry matter and lactic acid contents, and to reduce the pH and ammonia levels in treated silages. 

The less hydrophilic polyols and sugar alcohols can also be used as polar heads for the design of bio-based hydrotropes. Glycerol being widely available as the by-product of the biodiesel industry, it has received particular interest. 

BY-PRODUCTS. All of the by-products of the sugar beet industry can be used as livestock feeds. The resulting beet pulp can be fed wet, or it can be ensiled or dried. Molasses is often added to beet pulp to increase the energy content. Furthermore, beet tops and crowns— very top portion of the beet—are relished by livestock. These can be fed fresh, dried, or ensiled. 

The situation with regard to ethanol is much clearer there is long industrial experience in the manufacture of ethanol from wood, by fermentation of the sugars in the waste effluents of pulp mills, or of the sugars made by wood hydrolysis ( ). In the years following World War II, wood hydrolysis plants have been unable to compete economically with petroleum-based ethanol synthesis, mainly by hydration of ethylene, and they have been shut down in most countries. However, in the Soviet Union, we understand, there are still about 30 wood hydrolysis plants in operation (10). Many of these are used for fodder yeast production (11) but the wood sugars are also available for ethanol production. 

---