T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E U I S T R Y
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of chemistry and the allied sciences in the service of food law enforcement and control. A plea is made for the application of the elementary principles of scientific attack t o the large complex problems of food production and distribution. The food control chemist is, or should be, something more t h a n a laboratory analyst. His spheres of labor and of usefulness are co-extensive with the food industries of his state. CHICAGO
FACTORY CONTROL IN THE MANUFACTURE OF CORNSTARCH AND CORN SYRUP By A. P. BRYANT Chemist, Clinton Sugar Refining C o m p a n y
The number of industries in which a certain amount of chemical control is exercised is constantly increasing, and in those industries which have a more or less elaborate system the nature of this varies with the nature of the manufacturing process and even in the same line there will be considerable variation in its extent and details. I have been asked t o tell you in a few words something about the chemical control in the manufacture of corn-starch and corn syrup, a n industry which annually uses over ~o,ooo,ooobushels of shelled corn and produces from it a large variety of products, of which starch and corn syrup are the chief. The object to be obtained in a n industry of this sort is the recovery of as much of the starch of the corn as possible and the utilization of t h e remainder of the grain to the best advantage and with the least possible loss. The different steps in the process of obtaining the starch separated from the rest of the corn are all mechanical, but the completeness of separation is controlled only by analyses of the materials a t different stages, the results of which analyses serve as a guide for factory operations. In fact it may be said that these operations are based almost entirely upon the data furnished by the laboratory. It follows, therefore, t h a t it is necessary t o have not only accurate and representative samples, but also quick and accurate methods of analysis. In different factories the details and extent of control will vary somewhat, but the general character is the same. In what follows I shall attempt to describe very briefly the methods more particularly as practiced in one factory. The chemical work will naturally fall under four divisions: ( I ) Examination of supplies and raw products. ( 2 ) Control of factory operations. (3) Examination and standardization of finished products. (4) Special and research work. EXAMINATION O F SUPPLIES A S D RAW PRODUCTS
The extent to which supplies are analyzed and their quality or strength thus controlled will depend upon the extent of laboratory equipment and force; the analyses may be more or less complete and will follow t o a considerable extent similar control in other industries. There mil! be analyses of coal, lubricating oils, and general manufacturing supplies, which in this case include sulfur, soda ash, bone-black, muriatic acid, etc.; and finally the examination of the corn, i. e . , the raw product Each car of corn is carefully sampled and the moisture determined. Also, from time t o time, complete analyses are made of average samples of corn t o determine the a n o u n t of protein, oil, starch, water soluble matter, fiber, and ash present. Upon these determinations are based the comparison of the yields actually obtained with what should have been obtained, as well as the variation in treatment which may be required for most satisfactory operation COSTROL O F PACTORY OPER.4TIONS
The manufacture of corn-starch and corn syrup may be divided into three parts: the soaking of the corn; the separation of the different parts of the corn kernel (germ and oil, hull,
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gluten, and starch) and the manufacture of the finished products from these. The control in the soaking or steeping process consists in the regulation of the strength of the steep water, i. e . , t h e very weak sulfurous acid obtained by burning sulfur in a draft of air and dissolving the sulfur dioxide in a large quantity of water. The amount of sulfur dioxide is determined a t frequent intervals and the relative amount of sulfur burned and water used regulated according to these tests. Later in the process further tests are made t o assure the total elimination of the sulfur dioxide in t h e finished products. This sulfur water is used to keep the corn sweet during t h e period of between one and two days, while it is soaking in warm water preliminary to t h e subsequent operations. These involve first the tearing apart of the soft, soaked corn; then the floating of the germ on a mixture of starch and water and its removal from the rest of the corn; next the grinding of the remaining portion of the corn and the separation of the bran or hull from the starch anti gluten by means of silk covered shakers or reels; and finally the settling of the starch from the gluten on starch tables. These successive steps are all in the wet and are governed by the gravity of thc mixture of starch, gluten and water, and controlled by frequent observation. The completeness of each separation is determined by the analyses of samples, either taken automatically and continuously or a t frequent intervals by a sample carrier. As an example of the way the laboratory results are used a few illustrations may be given. The completeness of the separation of the germ from the rest of the corn is determined by taking a measured amount of germ-freed corn and adding i t to a mixture of salt and water heavy enough t o float any germ which might not have been removed in the factory process. The presence of floating germ indicates t h a t the starch and water was not sufficiently heavy in the factory operations and the gravity is then increased. On the other hand the presence of germ which will not float because it is weighted down with starch and hull indicates that the degerminating mills are not working properly and should be attended to. Again, a sample of the bran from the shakers or reels is tested for its starch content. This indicates the satisfactory or unsatisfactory operation as a whole. A duplicate sample thoroughly washed over silk bolting-cloth and then tested for starch shows whether any improvement t h a t ought to be obtained should be sought for a t the mills by closer grinding, or a t the shaker and reels by more thorough mashing, or both. The satisfactory separation of the starch and gluten is tested by determining the protein in the starch on the one hand and the starch left in the gluten on the other. Some light immature starch granules will of necessity be carried away in suspension with the gluten, but this must be reduced to the lowest possible amount. The starch, which is obtained as the final result of the operations already alluded to, is used for the preparation of the various kinds of starch (such as pearl, lump, powdered, laundry, etc.), for roasting to produce dextrin, or is sent to the refinery t o be made into corn syrup, or corn sugar. The gluten and bran are united, filter-pressed and made into gluten feed. The germ is sent to the oil house from whence, after due time, i t emerges as corn oil and corn oil cake or corn oil cake meal. The control work thus far outlined has to do simply with the completeness of the mechanical operations involved in the separation of the different component parts of the corn. In the refinery on the other hand a chemical change is involved in the hydrolysis of the starch under pressure and in the presence of a trace of hvdrochloric acid. In the manufacture of corn syrup the hydrolysis is carried only to a point where from 40 to 5 0 per cent of the starch has been actually hydrolyzed, the remainder being split up into dextrins. There are found both
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dextrose and maltose in the hydrolyzed products, but for control work it is sufficient to determine the reducing value of the product and report this as dextrose. The acidified starch milk of the desired gravity, usually 2 2 ’ B6. for syrup conversions, is run into a converter and cooked with live steam until the color reaction of a test sample drawn from the converter coincides with that of a similar sample tested in the laboratory and found of the desired degree of conversion or dextrose ratio. The operations of the converter are thus controlled directly by the laboratory. The charge, once having been brought to the desired test, is released into a neutralizer where sufficient sodium carbonate is added to neutralize exactly the hydrochloric acid in the syrup. The completeness of the neutralization is determined a t frequent intervals, but cannot vary one way or the other more than a trifle for this reason: there still remains in the starch a minute amount of gluten after all the previous treatments and this is kept in solution in the hot slightly acid syrup. Once neutrality has been reached, this trace of gluten, carrying with it a trace of oil and pentosans, separates, causing a “break.” A t this point the liquid can be filter-pressed and this residue removed, but either a trace of acid or of alkali prevents this; consequently, the neutralization in a way is fool-proof although there is a fine point of exact neutrality that can be determined only by laboratory tests. I n the manufacture of corn sugar, the operations ‘are similar to the above excepting that the action is carried further, until from 85 to 9j per cent of the starch has been hydrolyzed, depending upon the kind of sugar. The neutralization and subsequent purification, however, are practically the same as with corn syrup. The purification of the syrup is obtained by means of charred bone or bone-black and throughout the process until the refined and concentrated liquors are finished and ready for shipment great care must be taken to see that all conditions are the most favorable; that the gravities of the liquors are kept constant; that no contamination by dirt or entrance of wild yeast is allowed; in short, that all conditions are as ideal as possible. This is brought about by means of laboratory tests on average or special samples taken a t all stages of the refining and finishing processes. I n this way it is possible to detect and remedy trouble or irregularities, which, if allowed to persist, might affect the color or general appearance or even the quality of the finished product. For example, a leaking valve might allow raw starch to escape from the converter before it had had a chance to be hydrolyzed, but a test with iodine would reveal this. Or the sides of some of the tanks might become infected by wild yeast, but a s tests would show this long before any real trouble could be experienced, the source of the irregularity is thus discovered and remedied. Thus by constant watchfulness and frequent tests it is possible t o maintain uniformity and satisfactory operations in this most important department, but this eternal vigilance must not let up day or night. The finished corn syrup is concentrated in uacuo to a gravity of 42, 43, 44 or 45” B6. based on a temperature of IOO’F. These gravities are taken a t the vacuum pans, but samples taken to the laboratory serve as a check and keep the pan man lined UP.
The gluten and the bran separated as already outlined are united, the concentrated soluble matter removed from the corn during the steeping added, and in due time we get corn gluten feed. The chief function of the laboratory in connection with this is to determine the moisture in the finished product, and thus keep the product up to standard in this respect. The germ of the corn, removed in the first mechanical separation, is sent to the oil house where it is dried, ground, cooked and the oil expressed, the residue forming corn oil cake or corn oil cake meal as the case may be. A determination of the oil left in the cake or meal shows the satisfactory or unsatisfactory operation of the hydraulic presses or oil expellers.
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I n what has been said, account has been taken only of the material actually in process and recovered. It is necessary, however, to look out for losses. These are sought in the sewers. Inasmuch as the milling process requires a great volume of water, it is necessary to get rid of this a t various places. Wherever there is an outlet to the sewer a continuous automatic device is or should be placed and the samples tested for solids in suspension and solution. Solids in suspension are unnecessary loss and require immediate steps to remedy or obviate the condition permitting this. Solids in solution may indicate avoidable loss or a loss too small in amount or too diluted in quantity to recover. I n the refinery there is possibility of entrainment during boiling in the vacuum pans and the slight amount of syrup which would be carried over can be detected and roughly estimated colorimetrically, if desired, by use of the alpha naphthol test. Leaks in the steam tubes of the vacuum pans which might permit syrup to leak through when the vacuum is broken can be detected by this same test in samples of the condensed steam from the tubes. Similar tests will show whether the filter presses and the bone-black filters have been sweetened off properly before being washed to the sewer. By making tests of these waters, day and night, a very accurate control is possible of the conditions in the refinery, and, in fact, in the whole plant, which might lead to avoidable losses. SPECIAL METHODS AND TESTS
I n order properly to guide factory operations it will be seen that the laboratory must make many tests and that the results must be obtained in the shortest time conducive to a satisfactory degree of accuracy. This means that short-cuts and quick methods are required and that these shall give essential agreement with official methods. A few examples will illustrate’ htoisture determinations may be made in a vacuum bath heated by steam jacket a t atmospheric pressure in three hours. In determining oil in various products carbon tetrachloride may be used as an extractive reagent and the total time of extraction reduced to zl/*hours, the results agreeing very closely indeed with official results by ether extraction by the official method. This method has been used by the writer for many years and was described in the Journal of the Amevican Chemical Society, 26 (rgoq), 568. Another advantage of this solvent is its freedom from danger of combustion. Starch may be determined indirectly by malting in the usual manner, filtering on weighed filters and determining the loss of weight after thorough drying. This loss of weight corrected for moisture and water-soluble matter in the original material and for insoluble solids in the malt extract used may be taken as starch and is perhaps as accurate as the official determination of starch by the reducing value of hydrolyzed malted extract, and the time consumed is much less. Reducing value is determined volumetrically by a Fehling solution standardized by C. P. dextrose so that 25 cc. solution is completely reduced by 1 2 ’ / ~ cc. of I per cent dextrose solution. Protein is determined by the modified Kjeldahl method using copper sulfate. Where practicable 0.875 g. material is taken and the final titration with A’/Io alkali gives percentage directly, I cc. being equal to I per cent protein in the sample. The above are the more important control tests, but special tests suggest themselves for special cases. Colorimetry plays an important part in comparing colors of starch, syrup, and other materials with standards. In controlling the strength of the weak sulfurous acid used for soaking the corn and testing for its subsequent removal, considerable amounts of iodine solution are required. Owing to the increasingly high cost of iodine and potassium iodide, the writer has been using for routine work a solution of potassium permanganate standardized through sulfur dioxide against iodine solution. This solution works admirably for control work and yields a marked saving in expense.
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The results furnished by the laboratory show what is taking place a t different steps of the process through the factory, These results, however, must be coordinated and applied in order t o make them of value. From the results of the routine tests the foremen in the different departments of the plant can correct their respective operations so as to improve the results. At other times some unusual condition or combination of conditions may bring about unfavorable results, which will require special tests and analyses and perhaps more or less research work in order to avoid them. Once a certain kind of trouble has been experienced it becomes easy t o avoid this a second time, but in the manufacture of corn-starch and corn syrup, as of course, in other industries, it is the unexpected that usually happens. Consequently, the one in charge of operations must not only keep in constant touch with the laboratory results, b u t carry on such additional tests and experiments as seem necessary in order t o obtain the information which will permit getting the most satisfactory results from the plant. EXAMINATION AND STANDARDIZATIOK O F FIKISHED PRODUCTS
A complete analysis of the different finished materials serves as a guide for standardization. For example, the gluten feed and corn oil cake meal must be guaranteed to contain not less than a stated minimum of protein and fat and not more than a stated maximum of fiber. These limits will naturally be put a t such values that under the individual factory conditions they can always be attained unless for some very unusual cause. It is the function of the laboratory t o prove whether or not these guarantees are met, although for that matter the process control will give a very definite idea as t o this. The crude oil is analyzed €or its content of free fatty acids: if the oil is refined, a still further control must be exercised, both over process and finished product. The starch is tested for moisture and for impurities, which in this case are the other normal constituents of the corn, vie., protein, oil and fiber, lvhich should be present in the merest trace. Corn syrup will be tested for gravity and perhaps acidity. It is interesting to note that pure corn syrup has a trace of acidity, using phenolphthalein as indicator, due apparently t o some slight acidity of the dextrins or other inversion products formed in the hydrolysis of the starch. I t also has a trace of alkalinity, using methyl orange as an indicator, due to traces of sodium phosphate present in the ash of the syrup. With rosolic acid as indicator, it is practically neutral. In addition the syrup may be tested for its boiling properties as used with sugar in candy making, and its resistance t o discoloration when heated. This latter would be noticeably affected were the refining process insufficient to remove all but the most infinitesimal traces of gluten, etc. I n short, it is the duty of the laboratory to devise and execute the most rigid and severe tests in order that the syrup may be brought to the very highest state of purity. SPECIAL AND RESEARCH WORK
No industry is in a really healthy condition unless it is advancing along the lines of improvement of its products or development of new fields for their use. In the starch and corn syrup industry there is still opportunity for abundant research work and there will be found many new uses for the products already made and many new products discovered which can be manufactured from the constituents of the corn kernel. The number of different products is already large, including pearl and powdered starch, various kinds of lump starches, modified starches, soluble starches, dextrins of various kinds, corn syrup, several preparations of corn sugar, refined oil for table uses, rubber substitute, cattle foods and many other products. As regards improvements in quality, it may be said that the pure food law, which some ten years ago abolished the bleaching of corn syrup with sulfur dioxide, has been most beneficial as i t necessitated improvements in the refining process so as t o get a
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more highly refined product, and to-day corn syrup is whiter even than in the old days of bleaching syrup, and much better. I n fact, it is one of the most, if not the most highly purified food product that we have. In conclusion we may repeat that the manufacture of cornstarch and corn syrup, while almost entirely a mechanical process in its execution, can be guided and controlled intelligently only by the most thorough, rigid and comprehensive system of chemical supervision. CLIXTOK, IOWA
T H E CHEMICAL CONTROL OF GELATINE MANUFACTURE By J. R. POWELL Chemist, Armour Glue W o r k s
Previous to the present decade, chemical control in the gelatine industry was rather limited. The manufacturer bothered himself chiefly about producing a product that would give a sufficiently strong jell, and be brilliant enough in appearance t o satisfy a trade which was critical about these points only. With the recent awakening to the possibilities of better manufacture and control of all food products, a more exacting chemical control of gelatine manufacture became a commercial necessity. Once this control was established, it became, and still is proving of real assistance to the manufacturer, in addition to developing a product acceptable to the trade. Improved methods introduced have tended t o increase yields, improve what is commercially known as test, and conserve by-products, all of which gives the producer greater returns. As a result, what was once looked upon as a necessary nuisance will soon come t o be accepted as a necessary source of help. However, in outlining the precautions taken in this industry, many things will, be mentioned under chemical control, that, while properly so designated, are the outgrowth of long practical experience, and cannot be directly credited t o the introduction of chemistry. It is remarkable, however, as others have undoubtedly noticed in other industries, how many processes or tests practical men sometimes use, which, on first inspection, seem t o be without rhyme or reason, are found to be based on very sound principles, when given a thorough study. Control work naturally divides itself into three classes: ( I ) inspection of raw materials and chemicals, ( 2 ) control of the manufacturing process, (3) inspection of the finished product. RAW IIATERIALS AND CHEMICALS
Raw materials for the manufacture of gelatine, being byproducts of other industries, have been far from bring standardized, and the quality has been extremely variable. When the supply of materials was great, corresponding to the demand, and as a consequence, the price was correspondingly low, this variation did not worry the manufacturer so much. Margins were great enough that some variation in yield could be overlooked. As the demand for this material comes t o exceed the supply, and it becomes necessary t o buy on a competitive basis, the possible yield from such material becomes a vital point. As a result, inspection of such material for its actual value to the manufacturer is continually becoming more important. If the stock is t o be used only for glue manufacture, examination ends at this point, but that used for the manufacture of gelatine should be examined for impurities that would render i t unfit for making an edible product. For instance, arsenic and other heavy metals that are not permissible in the finished gelatine may be present in such quantities that the stock cannot be used, so it must be turned t o the manufacture of glue or technical gelatine. Other stock may contain only such impurities as can be removed by proper processing, and subsequent treatment must, a t least in part, depend upon the results of the examina-
