CIATION ACHERS
SOME CHEMICAL PROBLEMS AND PROSPECTS OF THE SUGAR INDUSTRY' ANDREW VAN HOOK College of the Holy Cross, Worcester, Massachusetts
A m ~ o u o HMUCH of the art of sugar making persists in present-day operations, the industry has always been extremely conscious of the benefits and necessity of scientific methods. The introduction of multiple effect evaporators in Cuba in 1855 (1) and the remarkable increase in sugar content of the sugar beet from about 4 per cent in Margraf's time2 to 15 per cent or more a t present are only two of many significant techmcal and scientific developments. The industry has always encouraged and supported research in its problems in various organizations. The beet research stations in practically every major European country, the Hawaiian Sugar Planters Association Experiment Station, the Audobon Sugar School in Louisiana, the Sugar Research Foundation, to name only a few organizations, illustrate this spirit of the sugar industry. Although the interests and problems of the sugar industry range from the A of agriculture to the Z of zoology, it is the purpose of this review only to outline some of the recent chemical and chemical engineering developments and to give some intimation of radical changes which are occurring in the agricultural methods of handling both cane and beets. Even though most of 'of these apply to the entire industry, it may be well to remember that normally about two-thirds of the world's production of sucrose is from cane. The cane and beet division each has its own unique and separate problems, however. ION EXCHANGE RESINS
One of the earliest uses suggested for ion exchange resins was the removal of mineral constituents from sugar juices, thereby facilitating crystallization and improving recovery by reducing the amount of molasses and in-
' Presented in part a t the 241st meeting of the New England Association of Chemistry Teachers, College of the Holy Cross, Worcester, Massachusetts, May 10, 1947. ' I n 1747 Andreas Margraf demonstrated that sucrose was stored in the root of the beet, although the same had been implied by de Serres in the seventeenth century.
creasing its quality as an edible product. These suggestions have been completely confirmed by laboratory and pilot plant experimentation, and several commercial-size units have been put into operation or are now under construction. Such full-sized equipment appears to be economically feasible (2) although there has been considerable discussion on this point (3). Inversion of the acid liquors during the cation pass is kept a t a minimum by employing cooled liquors and short contact times. Exchange resins have also been used to e l i n a t e undesirable ash constituents in the production of levulose from sucrose and molasses (4),and in the production of pectin from beet pulp (6). In a similar way, Biukley, Wolfrom, and associates (6) a t the Ohio State University have selectively adsorbed sucrose from both cane and beet molasses on suitable clays and reclaimed it in high over-all yields. Such chromatographic methods are very promising in general carbohydrate work. AGRICULTURAL ASPECTS
Led by recent radical changes in field methods in this country, the agriculture of the sugar beet industry is presently undergoing a revolution. Such changes seem to be an inevitable part of our evolving civilization, but in this instance their widespread adoption was accelerated by the exigencies of the past war. The established practices of planting, cultivating, and harvesting sugar beets were tedious processes, requiring much hand labor. With the aggravated labor condition attending the last war the industry was compelled to introduce methods to circumvent the difficulty. Mechanical methods of cultivation and harvesting had been developed, and the emergency. stimulated their further improvement and immediate use. At the same time, methods of segmenting the naturally clustered sugar beet seed assisted the mechanization tremendously, while the prospect of breeding single germ seed remains also another possible improvement. It has been estimated (7) that 18 per cent of the 194647 crop
50
JOURNAL OF CHEMICAL EDUCATION
Per cent in the United States was harvested by mechanical means, Dry substance.. . . . . . . . . . . . . . . . . . . 3 and that there will he a t least twice as many machines Carbonate ash.. . . . . . . . . . . . . . . . . . . 30 Dry substance available for 194748. These rather spectacular figures 10 " Sugar ............................ illustrate the rapidity of the change. A similar conOrganic nonsugam.. . . . . . . . . . . . . . . . 56 " Nitrogen (largely glutamic acid). .... 5 version is also taking place in the countries producing cane-particularly those where labor is scarce and wages A perennial wartime problem is the shortage of natuhigh (8). ral fats and waxes. This situation in the carnauba Cane is processed in the factory as soon as possible wax supply has been met partially by the extraction of after cutting, but beets are generally stored throughout wax from oane sugar filter muds (17). much of the average 100day factory period in order to assure unhampered flow through the factory as well as BOILING,a CRYSTALLIZING, AND MOLASSES to assure the completion of harvesting before the ground The unit operations of evaporation (18) and crystalfreezes. Considerable deterioration occurs during this lization (19) as practiced in the sugar industry have time, and much work has been done to minimize this waste. A combination of aerating the pile and white- been receiving considerable attention in recent years on washing the top layer seems to be most effective. Both account of their paramount importance in determining treatments serve to keep the temperature within the the plants required and the cost of operation ($0). The pile as low as possible and thus reduce the rate of res- production of sugar crystals of large size is most desirable since the centrifuging qualities of a massecuite piration (9). other conditions beine: the s a m e a r e better the larwr SYNTHESIS OF SUCROSE and more remlar th;: size of the crystal (21). ~ t l i s The synthesis of Sucrose has been accomplished by also believed-(81) that small crystals deteridrate faster Hassid and coworkers a t the University of California than large ones, on account of the higher dilution of the molasses film during processing. Viscosity effects will (10). A sucrose phosphorylase enzyme, from the bacunquestionably he involved in any complete explanation terium, Pseudomonas saeeharophilia, enables the comof the mechanics of molasses elimination. bination of glucose-1-phosphate and fructose to form Proper seed or "grain" is absolutely necessary in order sucrose. Beside proving the structure of sucrose to be old-glucopyranoside-P-d-fructofuranosidethis work re- to produce final crystals of any specified size and distriveals much about the mechanism of sucrose formation bution. While very little work has been done on the in living cells. Other nonreducing disaccharides can scientific aspects of this operation its technical importance seems to he implied in variousnewsystemsof graincan also he formed in the same way. ing and boiling. The Yearwood system (22) of external BY-PRODUCTS graining is accomplished with stirring a t constant Brix, The entire sugar industry is extremely conscious of and is particularly suited to low grade massecuites. Var"by-products in place of waste products," and is rap- ious other schemes (28, 24) have been proposed which, idly approaching the ultimate of utilizing the entire in essence, amount to the gradual subtraction of part of the massecuite to be used as grain for subsequent cane and beet plant. The major uses of cane bagasse are as fuel and for batches. The limit of such operations would be a conpaper and wall board (11, 12). Beet pulp remains a tinuous process with all attending advantages. lVehre (1, b) has continued to emphasize the advanstaple item as a stock feed throughout the world, but tages of proper management of vacuum pans. Conits high pectin content suggests attractive possibilities for this material and its derivatives ( 6 , l S ) . Sugar and forming with current chemical engineering practice, many sugar by-products are very promising in the rap- this is accomplished most completely and efficiently by idly expanding plastics industry (14). One of these means of indicating, recording, and controlling instruderivatives is aconitic aoid, CaHa (COOH)s, which has ments. Complete regulation of boiling pans is now a recently been reclaimed from Louisiana blackstrap in definite reality (Z5, 26). The inevitable end by-product of all sucrose orystalgood yields (16 ) . It forms plastics of high refractive inlization is molasses. The nature of this product has long dex and other characteristics particularly suited for been a matter of considerable speculation (27). Among safety glass and molded resins. The war and our efforts to assist in the rehabilitation the many theories proposed those involving some sort of of the war-ravished countries have greatly stimulated a sucrose complex are most prominent. The experimenour knowledge of the amino acids and their nutritional tal confirmation of this suggestion has been a matter of and medicinal uses. The increased consumption of some difficulty; but recently Van Hook (28,a)has examthese acids resulting from this new knowledge has given ined the X-ray diffraction patterns of several products, rise almost overnight to extensive enterprises for r e and from the complete inhibition of the sucrose comclaiming these materials from Steffens waste waters. The term boiling refers to the concentration of syrups after hi^ from beet sugar houses was truly a waste, initial evaporation. It is carried out in aepaxate vacuum pan and to some extent problem, until the present sharp the crystalliaers together with most of the crystallization. Boiling demand for its nitrogen com~ounds. The following comtitutes a strategic step in the production of both raw and reis a typical analysis (16): fined sugar from cane and beets.
.
JANUARY, 1948
51
Informal discussion, Am. Sugar Beet Technologists, 4th ponent at salt/sucrose ratios above one, he concludes general meeting, 1946,Denver, Colorado. that the molecular complex constitution is a likely one. ANON.,Intern. Sugar J., 49,56 (1947). . While the influence of adsorption on the crystallizaR o ~ o z E., , AND A. VANHOOK,PIOC.Am. Sugar Beet Tech., tion of sucrose from impure solutions is undoubtedly a 4,574-83 (1946). BINKLEY, W. W., AND M.L. WOLFROM, J. Am. Chem. Soc., vital factor in the crystallization process, very little 67,527,1789 (1945);69,664 (1947). significant work has been done on the matter until reYONT,L. Y., Suga~, 42, 28 (1947). cently. Coalsted (29) has demonstrated that the failWILLCOX. 0.W.. ibid.. 42., 26 11947). ure of sucrose to crystallize further from molasses is due FORT,C. A.,Am: Sac. sugar Beet Technologists, 4th general to the presence of surface-active impurities which are meeting, 1946,Denver, Colorado. AND H. A. BARKER, J. Am. HASSID,W. Z., M. DOUDOROFF, adsorbed on the surface of the crystals and thus inhibit Chem. Soe.,66, 1616 (1946). their growth. The suggestion many be refuted in view WEST,C. J., TJtilieation of Sugar Cane Bagasse for Paper, of the di5culty of actually forming adsorbates between Board, Plastics, and Chemicals," Sei. Reports 3, Sugar sucrose and many other substances (28 ,b), and behause Research Foundation, New York (1946). of the rather convincina evidence in favor of a definite BRITO.E. M.. Suoar. 41:. 28-30 fl946i ~ - ~ - ~ , ~ B.,Qoeier, 1, NO. 7,179-97 (1945). molecular-complex theory of molassesformation. How- (13) INGEL'MANN, ever, the distinction is a subtle one, and since the adsorp- (I4) LONG,L., "Sugm and Sugar By-Products in the Plastio Industry," (lod~li Sei. Reports 1, Sugar Res. Found., N. Y. tion forces must be recognized as being strong the whole subject should be very critically investigated. (15) VENTRE,E. K., AND COWORKERS, U. S. Pat. 2,359,537, The crvstallizina behavior of sucrose, from vure and , Nov. 3, 1944: J. Am. Chem. Soe.. 67.. 1 119451: ~ , IT. -~ , 8. -D. A.; A . I. C. No.132,Jan., 1946. from impure solu~ions,has been studied kiietically, most recently by Ingelmann (SO) and van Hook ($8,c). ~~,"~",","2.~:,~.I,~~,"dd";',"f77~&~,77 l7 he latter shows the cr~stallizatio?rate to be ProPo:(18) BADGER, W. L., AND R. A. LINDSAY, I&. Eng. them., 38, tional to the thermodvnamic activ~tvof the sucrose m 4 (1~46). 22 (1947) ,, 30. ..,--- -.,, M~c~LBE;W. L., ibid., 38, 18 (1946). solution; and accordingly, as first suggested by interJENKINS,G. R.,Tech. Comm. No. 3, Queensland Exp. Sts, ionic theory, may be slightly increased, although usution (1941). ally decreased, by the presence of electrolytes. The B I R K E ~L. , S., "PFOC.B. W. I. Sugar Tech.," abridged, growth is definitely a surface process, and diffusion Inl. Suoar J.. 47. 297 1945. YEARWO&,R. D. E., Int. Sugar J., 49,9'(1947). through the solution or solution viscosity is not a priDEVRIES,G. H., List~lC U ~ O V U56, T . , 124 (1937); C. mary factor in determining the rate of growth. The 7278; 32, 3184. same general conclusions are reached by Ingelmann, DUCOUDRAY, L. B., Sugar,41,36 (1946). who employed a dilatometric method instead of the HOLYEN, A. L., Ind. Eng. Chem., 34,123440 (1942). usual refractometer or microscope. CUITOMETBR-"Manufacturer's Likrature," Sugar Supplv Co.. London. It isa pleasure for the author to acknowledge the beneWORRYZEK,o., "Chemie der Zuckerindustrie," Springer, fits of association with the staff of the Sugar Research 1928. Foundation, Inc., in the preparation of this review. (28) VAN HOOK,A.,(a) Chicago meeting, A. C. S. 1946, Ind. ~~
~
~~
~
~
\
LITERATURE CITED (1) WEBRE,A. L., (a)"U.S. Piper" (U. S. Pipe and Foundry Co., Burlington, N. J.), Sept., 1941; (6) Ass. Sugar Tech. Cuba, 1945, 1946. L. B., Sugar,42,23 (1947). (2) PORTER,
En6 Chem., in press; ( b ) unpublished experiments; ( c ) Ind. Ew.Chem., 36, 1042-51 (1944); 37, 782 (1945); 38,50 (1946). (29) COALSTED, S. E., J. SOC.Chem. Ind., 65,206-8 (1946). (30) INGELMANN, B., Socke?.,3, No. 1, 1-20 (1947); 'The Svedberg Memorial Volume," Upsda, Sweden, 1944,p. 1.
