January, 1923
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Recent Progress in t h e Chemistry of Sirups and Molasses By F. W. Zerban RESEARCH LABORATORIES, PENICK & FORD, LTD.,INC.,NEW ORLEANS,LA.
HE: SUBJECT matter of this article is so closely interwoven with the chemistry of cane sugar and related carbohydrates that it is somewhat difficult to draw a line between the two. Although many advances in the sugar industry proper have a bearing on the sirup and molasses industry, we will consider here only those that are of direct application.
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sirup. Another interesting suggestion, recently made in Canada, is the hydrolysis of wood waste, and the use of the resulting molasses as cattle feed. A simple method for making invert sugar sirup from dates has been described by Patterson. NEWMETHODS OF PREPARATION OR
PURIFICATION
Unfortunately, the severe business depression of the last two years was unfavorable to a successful conclusion of the The world’s demand for food, and parnew developments just enumerated. Imticularly for sweets, during the war greatly provements in methods of manufacture of stimulated the sirup and molasses induswell-established products had a better try, as it did most others. Not only was chance of success under such conditions, the production of the well-established particularly where the changes needed did sirups from cane, corn, and sorghum about not entail much expense for new equipdoubled, but new sources of food sirups ment. The use of invertasein the manuwere eagerly sought. It was natural that facture of cane sirup, investigated and recin both Europe and America great interommended by the Bureau of Chemistry, est was aroused in the manufacture of an is gaining a foothold in the industry. At edible sirup from the cane’s closest comleast one cane-sirup manufacturer in petitor, the sugar beet. The undesirable Louisiana made a large proportion of his flavor of beet sirup, as produced in the output last season by the new method. sugar factory, had entirely prevented its The process is very simple, but its introdirect use as a food, but under the cirduction had been somewhat retarded by cumstances it is not surprising that many the lack of an active invertase nrennraattempts were made to prepare a palatable F. W. ZERBAN tion a t a reasonable price. Tgis *diffiand pleasing product from the beet. A - - _. culty has in large measure been overnumber of patents were taken out, and the importance of the subject a t the time is best shown by the come, and a rapid spread of the new method may be fact that ti book of 146 pages was written on it by Block. expected. The sirup, *insteadof being boiled directly to full Sherwood, as well as Ort and Withrow, found that those sirup density with about 71 per cent tota1 solids, is first evapparts of the beet which contain the undesirable flavors in orated to only about 45 per cent solids, the invertase added a t largest amount should be cut off, or that a preliminary extrac- 5 5 O , the mixture allowed to stand over night, and then boiled tion should be made before expressing the juice; the flavors to around 78 per cent solids. This sirup, of 35 to 10 per cent that still. remain should be removed by heating under pres- purity, keeps without fermenting ’or crystallizing. The iiqe sure and releasing the pressure a t intervals. The necessity of invertase is also advocated by Harding for the preparation of using high temperatures was also recognized in Europe, of invert sugar sirup from cane sugar. where, in addition, the use of acids for partial inversion was Another promising process, which is being studied in connecadvocated to prevent crystallization and improve the flavor. tion with scientific investigations on the colloid chemistry of While beet sirup seems to have been produced on a large sugar products, has been giveri attention by the Bureau of scale only in Europe, the sirup that seemed most promising Chemistry and the Louisiana Sugar Experiment Station. in this country and really reached the manufacturing stage This is the use of adsorbents, such as infusorial earth and dewas maltose sirup, containing up to 76 per cent of maltose colorizing carbons. Tests made by the Bureau of Chemistry and but very little dextrin. It is made by treating starch, on a small factory scale have shown that a clean and bright modified starch, or starchy materials with malt, and refining, sirup, of light color and pleasing flavor, can be produced by probably with the aid of decolorizing carbon. Maltose sirup filtering the entire cane juice with infusorial earth and evapois free from malt flavor, sweeter than corn sirup, heavy bodied, rating in vacuo, or in open pans if desired. The additional and does not crystallize. There have appeared newspaper use of carbon resulted in a sirup which on account of its accounts of other sweet sirups made from corn, but no authen- mildness and very light color “should win favor in those retic information has been available. gions where sweetness rather than strongly marked flavors is A very interesting product, in whose preparation malt is the quality principally desired.” Willaman reports that a also used, is the sweet potato sirup originated by the Bureau sorghum sirup factory in the North is using Filter-Cel for of Chemistry, principally with the idea of utilizing culls that filtering all of the juice, and has experimented with decolorizare not marketable. This sirup is of pleasing appearance and ing carbon also. The flavor of the product is said to be very color, arid has a characteristic flavor similar to that of the fine. Decolorizing carbon is now actually used instead of raw material. boneblack in a t least one large corn-sirup factory, and others Willaman has proposed the utilization of the inulin of the are experimenting with its use. Jerusalem artichoke, which can easily be grown commerA number of articles and patents have been published on cially for the preparation of levulose sirup, the sweetest known the purification of sugar products of all kinds by means of NEWSOURCES OF SIRUPS
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INDUSTRIAL AND ENGINEERING CHEMISTRY
decolorizing carbons and other adsorbents. Some wellknown old processes for the purification of beet molasses have lately been patented again, with a view of using the treated molasses for human food. One of them is the precipitation and removal of potash as acid tartrate, patented by Ronner, and the other the osmosis process, preceded by inversion and followed by boiling in the open, filtration and evaporation in vacuo, as patented by Cutler. N A T U RAND ~ COMPOSITION OF SIRUPS AND MOLASSES The old question of the nature of cane molasses has recently been studied again in Java. Since Prinsen-Geerligs’ classical investigations on the subject, cane molasses has been considered as a saturated aqueous solution of chemical compounds between sugars and salts. Van der Linden was the first to reach the conclusion, on the basis of equilibria studies, that cane molasses is in fact a saturated solution of sucrose in nonsucrose; but the work of Kalshoven, done directly after that, called attention to a source of error, consisting of the presence of very fine sugar crystals in Java molasses. Kalshoven devised a method for determining this fine grain by refractometric measurements, and a repetition of Van der Linden’s experiments by Helderman, with the necessary corrections, gave further strength to Van der Linden’s views. Helderman has since then shown in other ways that Java molasses does not contain any chemical compounds between sugars and salts at ordinary temperature. Tiemann maintains that the chemical molasses theory still holds for beet molasses. As in most technical fields, colloid chemistry has lately begun to play a more important part in the sugar branch. Much of this work, particularly that on juice clarification, belongs to both the sugar and the sirup industry, and is therefore mentioned here only in passing, such as the adsorption theory of clarification developed a t the Louisiana Sugar Experiment Station, and similar work by Dedek, Harloff, Herzfeld, and others. The Bureau of Chemistry has also taken a leading part in this field by applying dialysis and ultrafiltration to the det,ermination of colloids in sirups and molasses, a$ well as to the isolation of gum from beet molasses and from diseased sugar cane. This method has made possible a close chemical study of these gums. Helderman and Khainovsky in Java have found that the colloids in cane molasses, though small in quantity as determined with the ultramicroscope, have a decided effect on the viscosity. Treatment of the molasses with infusorial earth or decolorizing carbon reduces not only the color, but also the colloids and with them the viscosity. It was also shown that carbonation produces molasses of lower viscosity, lighter color and with a smaller number of colloid particles than does ordinary liming. Unfortunately, the ultramicroscope is not very reliable when dealing with emulsoids. The coloring matter of sirups and molasses has also received a greater amount of attention since the advent of decolorizing carbons, Investigations made a t the Louisiana Sugar Experiment Station have shown that the color of cane products made according to best practice is almost entirely due to the presence of polyphenol compounds and their iron combinations. These polyphenols are derived from constituents of the cane itself, belonging partly to the true tannins, whereas others originate in the anthocyanins of the rind and the saccharetin of the cane fiber. Only in overlimed products is a large part of the color due to the effect of lime on reducing sugars in the presence of amino acids, and in overheated products to condensation products of the sugars. The color of commercial cane sirups and molasses, even those produced on the same plantation, often varies considerably, but average analyses of large numbers of individual samples
Vol. 15, No. 1
have shown that there is a distinct tendency toward a mathematical relationship between color and purity. A very unexpected and surprising result has IateLy been announced by Sale and Skinner. They conclude from carefully conducted tests that, contrary to generally accepted belief, invert sugar sirup is about 11 per cent less sweet than the cane-sugar sirup from which it is derived. The precipitate that is always found when clarified cane juice is evaporated to simp has been studied by Brewster and Raines, who have found that its composition varies considerably; however, its total quantity increases with the amount of soil adhering to the cane when it is milled, and the precipitate is probably largely derived from that source. Vinson and Catlin have shown that the ash in sorghum sirup from dry lands is not any higher than in that from regions of greater rainfall. Browne has made the interesting observation that molasses and similar sugar products separate into layers, on standing, the lower ones showing a higher proportion of ash and organic nonsugars. This proves the importance of thorough mixing of samples to be analyzed. ANALYSIS The determination of total solids in sirups and molasses is still in an unsatisfactory state, because there is no absolute method. Considerable progress has been made, however, toward greater relative accuracy and toward speed. A rapid and easy method of actual drying in a specially constructed electric oven has been,devised by Spencer. Proper conditions for the drying of beet products o n sand have been worked out by Aikin. Newkirk has designed a pycnometer by which the specific gravity of molasses can be determined quite accurately. The use of the refractometer for determining apparent solids is increasing. At least one sirup and molasses company uses this instrument exclusively in its factory control; tests recently made by a corn-sirup concern have shown that the solids determined by refractometer agree more closely with solids by drying than those determined by the common hydrometer method. The refractometer has also been found to be well suited for the analysis of maple products. Atkinson recommends a wider use of the instrument on account of accuracy, convenience, and speed, and a committee has been appointed by the Sugar Division of to revise the ta.bles of refractive indexes of the SOCIETY solutions of various sugars. The refractometer is also used in the determination of fine grain in molasses by Kalshoven’s method. The latter has been critically studied by Dedek, Kraisy, von Lippmann, and Schoorl, and there is still difference of opinion about the correct procedure to be followed. Unfortunately, the Baume scale is still widely uscd in the sirup and molasses trade, usually without specifying whether the “old,” the “new,” or the latest Bureau of Standards scale is meant. The error in sucrose determinations in cane molasses due to excessive dilution on account of dark color, and to well-known other causes, has been overcome by Walker (revised by Brodie) , who uses Horne’s dry subacetate of lead and removes the excess of lead with free phosphoric acid in small enough quantity not to cause measurable inversion. Kalshoven and Sijlmans get light-colored filtrates by the use of basic lead nitrate, followed with aluminium sulfate. Saillard, who has lately again brought forward arguments in favor of his ‘keutral” double polarization method for beet molasses, reports that differences between direct polarization and Clerget value in these products are caused principally by optically active nitrogenous substances, and change from year to year with the nature and quantity of the latter.
January, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Bakker has successfully applied the inactivation method of reducing sugars by means of alkali to the determination of aucrose in honey. Methods based on the titration of dextrose with iodine are coming into more extended use. More concordant results have been obtained in this way in the analysis of potato-starch sirup than by the use of Fehling’s solution, and the method has also been applied successfully to the analysis of honey. A complete scheme for the analysis of technical invert sugar sirups has been published by Bruhns. A method for the determination of raffinose in beet molasses by the enzyme method has been described by Paine and Reynolds, and the acid method has been revised by Jackson. Schecker states that the most reliable results are obtained by first concentrating the raffinose through repeated precipitation with barium hydroxide, treating with carbon dioxide, and then determination by the Herzfeld method. Viscosity determinations on molasses have been made with the Fischer viscometer, as compared with the Engler instrument, and with a modification of the Arndt viscometer. The dialysis method of the Bureau of Chemistry for determination of colloids, and of gums in particular, has already been mentioned. The hydrogen-ion method of measuring acidity superseded titration in the corn-sirup industry, and the work of Brewster and Raines has paved the way for its introduction in the cane-sirup industry also. It has lately been found that the commonly and officially accepted correction factor in the determination of sulfated ash in cane sirups and molasses is erroneous; the factor is not constant, and is nearer 20 per cent than 10 per cent. There is no need of using the sulfated ash method a t all, as the direct ash method is in most cases just as rapid and convenient and requires 110 empirical correction factor. Adkins and Withrow have shown that, if the sulfated ash method is employed, it should be carried out with dilute instead of concentrated acid. Since the introduction of decolorizing carbons the determination of color in sirups and molasses has become of great importance. The Bureau of Standards has therefore inaugurated a fundamental study of the light transmission of sugar products, and has already worked out a reliable method for color determination. The ordinary color matching instruments have been found to be of no value for the purpose, and some sori, of spectrophotometer must be employed. According to Kauffman, caramel determinations in sirups and molasses are meaningless, and the only method that has any value for comparative purposes is that of Ehrlich. Determination of electrical conductivity by Snell has found an important application in the detection of adulteration of maple sirups. The question of detecting the presence of technical invert sirup in honey has not been definitely settled; a new simple test, using resorcinol and 0-naphthol, has been described by Litterscheid. UTILIZATION The Steffen method of extracting sugar from beet molasses is now universally used in this country. Potvliet has shown, however, that the baryta process (used in Canada) and the strontia process have certain advantages over the Steffen method. The lead saccharate process, experimented with two years ago in Michigan, has evidently been abandoned again. Other, old and new, methods of sugar extraction from molasses are at intervals suggested and patented, but none of them seems to have found favor of late. The profitable disposal of the large quantities of final waste molasses from both cane and beet is quite properly receiving more and more attention. The two main reasons for this activity are the threatened danger of a scarcity of gasoline in the not distant future, and the low price of molasses since the close of the war period. I n certain tropical countries gasoline is already so expensive that the use of
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automobile fuels containing material percentages of alcohol has become an actuality. The alcohol produced from molasses is very simply and easily converted into a practical motor fuel by the admixture of ether which is made from part of the alcohol produced. Pyridine, kerosene oil, and ammonia are the common denaturants. Wherever the new fuel has been carefully manufactured, it has proved a complete success. In the United States conditions have not yet advanced to the point where alcohol motor fuels can successfully compete, but interest in the matter is constantly increasing, as is well demonstrated by the large number of patents, and technical as well as popular articles on the subject. In Europe a number of chemical products are now being manufactured from beet molasses and in this country some work has been done along the same lines. Special fernientation processes, or dry distillation, followed by chemical treatment, are being used or have been proposed for the production of acetone, glycerol, methanol and higher alcohols, fatty acids, ammonia and the methyl amines, methyl chloride, cyanides and other salts of soda and potash, and similar chemicals. Some of these, such as glycerol, butyric acid, nitrogenous compounds, and potash salts can also be made from the distillery slops. The production of potash from the latter was a thriving industry during the war, but has come to a complete standstill again. Whitaker advocates the use of silicon fluoride or hydrofluosilicic acid a s a bactericidal agent in fermentation, and also for precipitating the potash from the molasses itself, instead of making it from the slops. While the manufacture of fuel alcohol from molasses represents the largest potential market of the future, molasses may be profitably utilized in other ways. Arnstein suggests a larger use of molasses for the manufacture of yeast. The foodstuff market absorbs considerable quantities of molasses, whenever it can compete with grain. As a direct fuel, molasses has in most cases been disappointing, but von Stietz has recently designed a special furnace which will burn the molasses properly. Molasses is used as a fertilizer with good results in Mauritius, whereas in other places it has been found of little or no value. Mixtures of molasses with other residual products have lately been tried out in Java, likewise with very poor results. This account would not be complete without mentioning the “Reading List on Molasses,” compiled by C. J. West, comprising a complete bibliography on the subject up to 192Q. Further progress in the sirup industry, particularly cane and sorghum, will probably be in the direction of standardization, and of the manufacture of products that have a n appearance and flavor acceptable to the consumer outside of the restricted area where these sirups now enjoy their greatest popularity. The use of molasses will gradually increase as time goes on and as gasoline becomes scarcer, and it is not beyond the range of possibility that the molasses, now a drug on the market, may yet rival coal tar in value as the source of a variety of important chemicals.
Royal Society Medal Awards Among the awards made by the President and Council of the Royal Society (England) are: The Copley medal to Sir Ernest Rutherford, for his researches in radioactivity and atomic structure; the Rumford medal to Prof. P. Zeeman, for his researches in optics; the Davy medal to Prof. J. F. Thorpe, for his researches in synthetic organic chemistry; the Buchanan medal to Sir David Bruce, for his researches and discoveries in tropical medicine; and the Hughes medal to Dr. E. W. Aston, for his discovery of the isotopes of a large number of the elements by the method of positive rays. The Royal medals have been T.R. Wilson, for his researches on condensaawarded to Mr. tion nuclei and atmospheric electricity; and to Mr. J. Barcroft, for his researches in physiology, and especially for his work on respiration.
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