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T,VDVLSTRTAL A S D ENGINEERISG CHE;VIISTRY
Vol. 22. s o . 10
The Agar Industry in California' G. Ross Robertson L - N I V E R S I T Y OF CALlFORA1.A AT LOS .kSGBLES, C A L I F .
CCORDISG to legend, The standard Japanese technic in the industrial lidium are also used , but a Japanese emperor preparation of agar from Gelidium sea moss has been these usually are scant in and party , traveling adapted to modern American plant practice, in San quantity or give inferior prodin the mountains, were maDiego, Calif., by the American Agar Company. Folucts. I n the orient certain rooned in a snowstorm, and lowing the discovery of extensive beds of moss on the other TTarieties are found in Pacific coast, a modernized process, featuring artificial accepted the hospitality of a good commercial quantity. peasant family. Anxious to refrigeration and efficient washing, has been developed. Products of still lower quality offer the best, the humble host The relations of chemical and physical structure of come from allied genera, but DreDared an abundance of agar to new Droblems of manufacture and use are disthese are not made on the his choicest delicacy. seaweed cussed. American side. jelly. These plants have been Much of the food was left over, and had to be thrown out. studied in detail by *Japanese taxonomic botanists, whose This was an unprecedented act in thrifty Kippon, but it led t o publications, some of which are out of print, are almost discovery. The discarded jelly lay upon a shrub where it the only source of information in the field. Apparently froze during the night. Immediately thereafter came a thaw. nobody on this side of the Pacific has taken up the and the householder was surprised to see the frost-bitten jelly Rhodophyceae as a serious botanical problem. The new collapse, the watery part leak away, and the remainder shrink agar industrialists are thus at a loss t o identify some of to a glistening, crinkly, papery mass of trifling weight. the moss offered for sale. It is likely that there are varieFortunately the fnountaineer was bitten by the research ties quite unknown in Japan. More particularly is felt the bug at this point. He discovered that the dried jelly could lack of knowledge of locale, life habits, etc., which would be restored to dessert form, good as new, if it were merely greatly aid the industry from the scientific side. heated again with water and cooled. The agar moss has been found as far north as Monterey, quite reaching San Francisco. Southerly it I n this may, says the legend, arose the great agar industry Calif .-not of Japan. To this day operations are conducted much like reaches Magdalena Bay, Mexico. The San Diego operators those credited to the mountaineer. Sea moss is taken to the estimate that about half of the available supply, roughly mountains for the December-February period, and advantage figured, occurs below the Mexican line. The California intaken of the succession of frosty nights and clear sunny days. dustry is licensed under export tax to harvest the Mexican The moss is extracted with boiling water for several hours, and coast, and pays a small fee to the state of California for simithe extract strained through a coarse medium. The con- lar privileges in United States waters. Just at present a gealing to jelly form, freezing, thawing, de-watering, and dry- large part of the crop is coming from Cape Punta Banda, ing follow the idea given in the story. Unfortunately, of just south of Ensenada, Mexico, and from the Los Angeles course, containination of the product is inevitable, to say harbor breakwater. nothing of a seaweed odor which naturally persists through the Harvesting Difficulties process. The product is, nevertheless, valuable and much The limited output of the moss harvesters i s now the prized as a part of oriental diet. greatest problem of the California agar industry. At presCalifornia Takes Notice ent $180 per ton is most gladly being paid a t the door for crude air-dried moss. By the time the agar manufacturer The discovery by Japanese fishermen of agar-bearing sea washes out the salt, rejects the shellfish, and discards the nioss in quantity on the Los Angeles harbor breakwater led pebbles which the moss fisherman forgot to discard, the into a small establishment in simple oriental style in the near-by trinsic cost of the colloid itself runs high. Only one sixth to town of Glendale. It was quite obvious that California had one fifth of the crude weed comes through as refined agar. plenty of sunshine by day, but not enough frost by night, for This establishes an initial raw material cost of nearly 55 cents application of the standard Japanese process. Hence came per pound at the start of the factory process. the call for artificial refrigeration. As a result the operations It seems to be almost impossible to harvest the moss by attracted the attention of American industrial experts. The machine, although a great deal of mechanical ingenuity has enterprise was re-financed and moved to commodious quarters been expended on the problem. The rough seas which surge in San Diego, a point more centrally located with respect to over the best moss beds are the undoing of complicated mowraw material. Here now is found the only agar plant on the ing machines. There seems to be nothing equal to diving western hemisphere. It is almost needless to say that an and handpicking in deep water. I n shallow situations entirely new assembly of modern machinery has been de- special hooklike rakes are effective. The turbulence of the veloped to meet the situation. waters wems to be an essential point in the growth of the really valuable beds. Sources of American Agar The labor problem is accordingly acute. Harvesting moss The principal source of agar on American shores is the is no job for water-front loafers, but requires hale, hardy, and maroon-red marine alga Gelidium cartilagineum, shown in the thoroughly industrious men who know the sea. The Japaillustration. It is very commonly collected in small sprays nese are just the people to handle the situation, and have a by vacationists on beaches of southern California, as a t Laguna natural advantage in oriental production. Beach and other popular resorts. The plant grows on rocks Possible Supply in tuft or bushlike masses in the more turbulent waters from The California operators estimate that a steady annual low tide inark down to 60 feet depth. Other species of Gecrop of 1000 to 2000 tons of moss could be harvested, count1 Received August 2, 1930.
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October, 1930
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IXDZ7STRIdL A S D ESGISEERI,VG CHEMIXTRY
Quality of Product ing both tlie California and Lower California fields. This would take care of a considerable part of the world demand A real filtration of .i.iscous agar liquor is practicable 0111~ for agar. At present Japan produces nearly the entire with modern pressure equipment. The American agar is thus morld supply of the colloid. There will need to be iie1~7 applications of the material before so great a new production free froni sticks, sand, etc., which may escape the relatively coarse screens of the oriental factories. Equally important can be taken care of. is the effective thawing and washing process, in which the frozen jelly is drained so effectively that it loses tlie seaweed The American Process taste characteristic of so much of the old-world product. The dried, haled sea moss as delivered by the fishermen On the other hand, the best S o . 1 agar from Japan has a is washed with fresh water in open vats for 24 hours to eliini- niore beautiful, whiter appearance than the American product. nate niost of the ordinary marine salts. It is then transferred This is due to tlie long period of sun bleaching, and the relative by crane in iron dump baskets to one of five closed digesters, freedom from so much contact with iron vessels. American in which it is digested wider steam heat for 6 hours in a fairly agar is grayish in tint. The whiteness of the oriental concentrated agar liquor prepared from the nearly-spent weed product is attained, however, at the expense of some chemical of a previous batch. Following a modified countwcurrent deterioration-probably hydrolysis if nothing else. The principle, the weed receives two more extractions, 8 and 13 American product thus has a higher jellying power. and will hours, respecti\ ely, first with dilute solution and finitlly with absorb more water. water. The hot agar liquors so prepared, are treated with both Chemical Structure charcoal and Filter-Cel, and filtered at about 30 pounds presThe material known in America as “agar” acquires its name sure in an ordinary filter press. The clarified matc~ialcongeals readily to a firm jelly upon return to room temperature. as an abbreviation of the Malay term “agar-agar,” which A variety of congealing containers has been used, biit in any simply means jelly. Although the chemical structure of agar is not known with case the agar gel is fed with the aid of a pump to a shearing machine. The gel is received into standard ice cans in the form certainty, and has been ignored generally in nianufactiire, of short rods or similar fragments of pulp. This part of the it is likely to have considerable bearing in industrial research, process deviates from thta Japanese method, where the jelly is both of preparation and applications, which is soon due. extruded froni a hand pump in a macaroni-like form, and is not cut up. As a result the finished Japanese product occurs in long strips instead of fine flakes as in American production. Frozen Jelly
The cans filled with jelly are frozen in brine tanks in the manner common to conirnercial ice production. d 300-pound cake, so prepared, contains about 3 to 6 pounds of agar. The cakes of frozen jelly are cut up finely in a rotary ice crusher, and the granular mass cautiously thawed in a stream of water leading to the washing and filtering apparatus. Care is taken to keep the temperature well below 10”C. throughout this thawing process. A rotary filter of special design handles the sludge of disintegrated pulp and rejects the considerable quantity of soluble material. The pulp still retains a quantity of water, which no doubt would retain salts; but tlie washing with fresh water dialyzes out most of tht.se salts. The cutting up of the jelly, disintegration by expansion of ice crystals, and crushing of the ice blocks all coiubine to giye an unusually fine state of division in the agar pulp. I n this situation the process of dialysis is most effective, and the final product thus exceptionally frpe from soluble impurities. -4 special dehydrator has been developed to handle the moist agar pulp. Two aluniinuin cylinders, 35 feet high and 3 feet in diameter, receive the met flakes from a screw conveyer. An upward hot-air blast agitates the heavy pulp particles until they are light enough to rise over the top of crlinder N o . 1. They then fall through a fabric pipe to cylinder KO.2, where the dehydration IS finished. The final comiiiercially dry agar is a fluffy mass of extremely low apparent density. As suggested in the ~lliistration,the flakes roll and warp into crinkled m a w s which are very readily disperqed in hot water when desired for use. For some applications even these agar flakes are too coarse, and a part of the product is ground and sifted to granular powders of varying fineness. On account of the toughness of agar, this operation IS not so readily accomplished as with salts. Further details, both of California manufacturing methods and application to foods may be seen in a paper by lfackinnon (5‘).
Agar Sea Fern, GeIidiurn carrilagineurn
A consensus of opinion identifies agar as a galactan, or polysaccharide in whose molecule numerous galactose units are united in a nianner suggestive of the grouping of glucore nuclei in cellulose. A small proportion of other sugars complicates the situation, so that agw reactions have iiot been uniform in all research laboratories. Combined with the Carbohydrate mass is a m a l l proportion, usually nearly 3 per cent of sulfur. This is apparently in the form of organic sulfate. Furthermore, calcium and magnesium form an essential part of the substance. Kithout these or similar bases the material is useless as a practical colloid. The firm bonding of all this material leads to the present assumption that the main carbohydrate niolecular niass is combined as an ester with sulfuric acid. Inasmuch as but one of the two acid groups of sulfuric acid is esterified, the second is free to form a calcium salt, of the following general forinula: /-SO---@
R \ ‘
‘ca
3-s 3L--c, /
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INDUSTRIAL AND 8N@INEERING CHEMISTRY
Further strnctural details have been described by Fairbrother and Mastin ( 1 ) Chemical Behavior It is not difficult to understand that agar, being a calcium salt. is rather stable in weakly alkaline solution, but might easily undergo simple ionic, and perhaps organic, reactions in acid media. This situation id probably related to one of the principal American applications of the colloid-vis., its use in the treatment of co~lstipation. Taken into the alimentary canal, agar swells greatly, but is not digested. It furnishes a large volume of fecal matter and stimulates proper intcstinal action without chemical irritation. A p parently the material passes out of the acid environment of the stomach long before any appreciable amount is hydrnlyzed, and in the alkaline fluids of the intestines is not h y d r e lyzed at all.
Amer(eaa Flske hear
In the California plant care has been taken to eliminate the acid treatment which has been common in oriental praetice. Apparently the use of a little vinegar, and later of sulfuric acid, was considered in the orient to be of mechanical sssistance in the preparation of a good-looking product. Such treatment, however, causes partial hydrolysis, and may be the cause in some cases of the inferior jellying power of oriental agar in contrast with the American. Moreover, the wear and tear of sun radiation hy day and rain and snow by night is much harder on the agar molecule than the prompt and rapid processes used at San Diego. Cloudiness of Agar The slight opacity of agar gels has always thrown them into a position of disadvantage in competition with gelatin. Suspicion has been thrown on the alkaline-earth component as possible cause of the opacity, and experiments have been carried out to free the agar-acid by the admixture of hydrochloric acid to the ordinary colloid product. While this is readily accomplished, the jellyiug power of the material d i e appeam and only a viscous liquid remains. Probably considerable hydrolysis occurs. It is probable that hydrolysis is not the only cause of trouble in the attempt to eliminate the alkaline earths. It is quite possible that agar derives its principal virtue, that of high gel st,rength, from its strnctnre as a salt of an acid of very great molecular weight. There are probably colloid-ion phenomena resembling those described by McBain in solutions of cold-water soaps. The possibility of substitution of sodium or potassium for the alkaline earths in the agar salt group has been investigated to some extent @), but. has not yet reached industrial attention. Such substitutions may have an important bearing, not only on clarity of gels, but also on the viscosity and surface tension of the more dilute solution of the colloid.
Yol. 22, No. 10
Physical Behavior
As little as 2 g r a m of agar, dispersed in a liter of hot water, upon cooling will set t o a jelly. Freezing destroys the jelly structure. Upon thawing, the shreds of agar which had lain between the ice crystals will absorb about four times their weight in water. If the temperature is kept low, however, no more water is absorbed. The swollen agar particles do not stick to each other, even upon being packed or squeezed tightly. Reheating promptly restores the jelly structure. The more dilute mixtures, or sols, are quite viscous, but do not show a very low surface tension. This fact bears consideration in any attempt to substitute agar €or some expensive high-class emulsifier. It is probably advisable to combine a substance of great power to reduce surface tension with agar in order to profit by the major virtue of the latter-vis., an increase in viscosity. The nower of sear to swell t o larw volnme in cold water is
salts out of the mass. The use of glass or enameled industrial ware would undoubtedly permit the production of pure white or colorless agar, if a real demand should come for such material. Experimental batches of such character have been prepared in the San Diego laboratory. Agar is so highly absorptive that the slightest discoloration is easily acquired and quite ohvious to the eye, although the actual percentage of colored impurity may be almost infinitesimal. Applications
A large part of future investigation will concern applications of agar and by-pr0duet.s. Among these are the familiar petroleum-agar emulsions, which may be improved. In these mixtures the agar is used, not in its ordinary medici.. nal applicat,ion, but rather in cooperation wit,h gum arabic or like preparation as a protective colloid. With this aid the petroleum lubricant is kept dispersed in the alimentary canal and does not cause leakage. Unfortunately some concerns have led the retail purchaser to believe that he was getting a substantial amount of agar in these bottled proprietary medicines-an assumption not borne out by analysis. Very much remains to be done in the investigation of the applicability of agar to salad dressing, table jellies, ice creams, confections, coating of textile fabrics, and in general any situation where thickening or gelation is desirable. The substitution of agar for a portion, not necessarily all, or some expensive colloid may be feasible without reduction of efficiency. Unlike pectin, agar requires no sugar to make it jelly; and a much smaller quantity of the colloid preparation will do the work. Unlike gelatin, it does not require special refrigeration to form a firm jelly. Spent Weed The eousiderahle residue of spent weed is finding some u8e as a fertilizer, since the nitrogenous part of the sea plant is left
XXDI;;STRIdL A S D EXGINEERING CHEMISTRY
October, 1930
behind. Inasmuch as its sodium chloride has been almost entirely washed out, but not its lime content, it offers promise as a n ingredient in mixed poultry food. Undoubtedly i t may also serve the fiber-board industry. Other Seaweeds
Common brown kelp, or seaweed, does not yield agar-at least not in appreciable quantity. It does yield, however, colloidal material of quite different character, such as the elginic products. The quantity of common weed is so enormous that a much greater industry could be developed if the market should require it. Tlre initial development of this industry is already started in the San Diego district. During the World War a considerable amount of aliphatic acid products, including acetic anhydride, acetone, propionic acid, and the like, were made near San Diego. The process involved fermentation of the weed. The processes
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are not economical with peacetime prices, however, and this industry is indefinitely suspended. It is quite possible, on the other hand, to produce the more unusual acids such as butyric, valeric, and higher members of the fatty series, in quantity from kelp. Bibliography
Further details of the manufacture and purification of agar may be seen in publications by Fellers ( 2 )and the Department of Commerce (4). Literature Cited (1) Fairbrother nnd Mastin, J . Chcm. Soc., 123, 1412 (1923).
(2) Pellers, J. IND. ENQ.CHBM.,8,1128 (1916). (3) Mackionon, Food I n d . , March, 1930. (4) “Methods of Manufacturing Agar-Agar in Japan,” in Commerce Rcpls., October 10, 1927.
Dust Control in Phosphate Rock Grinding’ W. H. Gabeler DAVISON CEQMICAL
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T THE Baltimore plant of the Davison Chemical Com-
pany on Curtis Bay phosphate rock from the company’s Florida sources is treated to produce superphosphate. The first operation after the raw material is unloaded to bins is the pulverizing of the rock for the acidulating process. The equipment for this purpose consists of twelve Raymond mills with air separators discharging to an intermediate storage bin. M7hen placed in operation, there were two features which required adjustment. The first mas the irregular load curve on the mill motor, which was corrected by providing mill feed control from a pick-up actuated by a solenoid in the
Figure 1-Dust
Received June 26, 1930.
which were not precipitated in the cyclone. The dust discharge from these twelve vents, shown partially in Figure 1, was a serious nuisance to the plant and neighborhood, as well as constituting an appreciable loss of material. Preliminary Experiments
T o remedy the dust discharge a number of experiments were tried, beginning with the simplest and least complicated methods. The first plan was to close off the vents and run the air-separation systems without excess air. Table I shows a
Nuisance Created by Cyclone V e n t Air before Installation of Air Filters
mill motor line. The load curve on this motor is now uniform, to give maximum grinding capacity, which averages about 4 tons per hour. The second feature of the system which required remedy was the dust discharge in the vent air from the cyclones. This vent airt amounted to about 1000 c. f . m. per mill, and carried with it the extreme fines from the grinding operation 1
BALTIMORE. MD
few comparative operating data for one system operating venting and closed. A number of objections to this system were revealed under operating conditions, of which the most serious was the increase in the moisture content of the circuit air, as the moisture in the material was liberated during pulverization. I n a comparatively short time saturation was approached, and consequent condensation occurred in the exposed piping and cyclone.
