A Staff-Induetr~ Collaborative R e p o r t . . M. L. KASTJCNS Asmchta Editor
W .
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F. A. BALDAUSKI in Cohhoratioa with
lTHOUT a doubt DWL’E oldeat manufactured food product IE milk. It is almost equally certain that nhortly after the first milk WBB collected nome prehintoric experimenter found tcollect an oily layer on the that, on standing, the liquid would h top and ultimately would separate into a rubbery curd and a watery fluid. This fundamental observation WBBthe baeis of the dairy induntry and its recently developing by-product satellite. The early dairyman EOOU learned to make butter from the cream layer and cheese from the curd. U t i l h t i o u of the watery whey esoaped him for thousands of yews. Excapt fot a few SOattered 8ucoe88es at “whey eheeaea,” he either threw it away or fed it t o his livestook. Lata in the last century the dairy chemist 6mt learned to recover milk sugar economidly from this ancient waate product, and still more recently he mastered the s e p ration of whey prokina (14). The preparation of milk for the market ie today one of our largest volume p r o d g induatriea. About 14 billion gallons of milk containing 16 billion pounds of solids pass through the d a i i of the United Btatea each year (80). Compared to ita giant parent, the dairy ohemicala industry is still an inaisnificant infant. It haa, however, an impressive potential for growth. Like all by-product indubtries its raw materisl is eesrmtislly a reclaimed waete. However, moat
Chemical Division, S k # i d d Farm Co., Inc., Nom‘ch, N . Y. “waste” material^ have only limited availability. The d a i i chemists have a supply of about 4 billion pounds a year of milk solids on skim milk. buttermill. and whev which is not now used
for food ($4). Accurate h r e s are di5cult to derive because of overlaDDing in the reported categories and wide Buctuations in the ty&a or products manufactured 88 market conditions change. About 70% of the production in the total milk solids is probably uwiaed as high &ciency food products for human conaumption. Auother 20% is condensed or dried for animal feed. T h e remainder, ne skim milk, buttermilk, or whey is either dincarded or returned to the fama for auiumI feed. The mat average production of 20,oao,oaopounds of oasein,4o,~,oao pounds of laatoae, and 164,aOO,@Y.l pounds of powdered whey barely scratches the available supply (IS). The failure to utilize thia vaat store of raw msterinl cannot be attributed t o lack of i n w on the part of the dairy industry. During the la& a0 years, prugresaive milk pmcamm haw p ~ a c 8iutently sought profitable outlets for theae msterisls, and IYJ increasingly stringent sotipollution legislation haa made dbpoasl of whey dS.cult in Bone looalitiea, this interwt hse been inten& However, the evoiutiou had to wait on the development of modern processing techniques to replace ancient, hand-operated,
a.
1258
INDUSTRIAL AND ENGINEERING CHEMISTRY
batch type processes and reduce production costs to a reasonable level even with a waste raw material. Continuous casein-making machines, introduced in the twenties and thirties, with improvements in evaporators and drying equipment have made the milk by-product industry truly a chemical process industry and given it its present economic promise (5, 9 ) . The development of modern tank truck transportation has also contributed by making it possible to collect milk over wide areas for processing at large central plants. Transportation costs still make the collection of cheese whey from isolated plants uneconomical. However, good products, even cheap good products, must have markets. The search for uses for pure milk proteins and carbohydrates has been both intensive and extensive. I t has ranged from textile fibers to paints, to bacterial nutrients. The search has met with mixed success. I n most applications the milk products must compete economically with vegetable proteins and sugars, sometimes also derived from process wastes. HOTever, continued research, both in processes and applications, by the highly skilled teams now engaged with these problems will undoubtedly find new economic outlets for the billion pounds of milk solids still being used so inefficiently.
In view of this irregular supply of raw material the Norwich plant is designed so that it can process in excess of 60,000 gallons of milk a day on a 24-hour operating basis. The plant operates a t optimum efficiency a t a rate of 40,000 to 45,000 gallons of milk per day. However, even when operating a t a lower rate, milk is never held in storage for more than 6 to 8 hours before being introduced into the process. Once processing is begun the material is carried through to a finished product without prolonged holding. Aside from the desire to ensure sweet cream after separation, the plant operators havc found that completely sweet milk is much easier to process in the chemical operations than milk in which some lactic acid has formed. Physically, milk is a combination of oil-in-water emulsion, colloidal suspension, and aqueous solution of organic and inorganic compounds (Table I). This may explain why, after undergoing intensive study, it still remains very poorly understood. The fat is the simplest of the components to remove. Tinder the influence of heat, agitation, acceleration, or a combination of these agents, the emulsion is broken, and the butterfat separates out.
SHEFFIELD FARMS NORWICH, N. Y., PLANT
The Sheffield organization has made important contributionv to the utilization of milk by-products. The Sheffield continuous process for the manufacture of casein is now the most widely used automatic process in the industry ( 6 , 16, 16). Sheffield pioneered in the large scale production of hydrolyzates from milk protein (8) and introduced these materials as nutrients for antibiotic cultures. Under a recent reorganization the former Chemurgic Division has become the Chemical Division and its headquarters relocated at the site of the Norwich, hT.Y., plant t o be described in this article. The reorganized division plans gradually to broaden its scope in keeping with its changed nomination. It is already operating at four locations other than Norwich, in S e w York and Vermont. Accelerated research activity at the parent company’s research subsidiary, National Dairy Research Laboratories, Inc., and in the division’s own facilities should reveal new products and new applications for existing products which will enable the division to utilize a greater percentage of the process effluents available from the dairy industry
~
The basic raw material on which the Norwich plant operates is whole, fresh milk seldom more than a few hours from the COT. As a process raw material it has certain disadvantages. Its composition varies with the season of the year, with the f e d supplied to the cow, and from cow t o cow. Fortunately the intake of the Sheffield installation is sufficiently large that the latter two types of variations tend to average out. The seasonal variations largely affect the fat content of the milk which is taken out in the initial cream separation and is not involved in the chemical operation. However, seasonal irregularities, assoriated with the number of cows coming into production and the change to fresh feed in the spring do influence the protein and carbohydrate recovery. Variations in the available quantity of raw material are murh more critical. The milk processor, unfortunately, has little control over the manufacturer of his raw material. Cowvs are exceptionally docile creatures, but they cannot easily be regimented into a regular production schedule. The volume of milk supply regularly varies by a factor of 1.5 to 3, between the early winter slack and the spring flush. Effluents from processes that operate only on “flush” milk are therefore available during only part of the year, Cheese whey, which may be processed to recover lactose and whey proteins, is usually available in large volume during the late spring and summer but contracts markedly in the winter months.
~
TABLE I.
.
Raw Material
Vol. 44, No. 6
~ ~ N A L Y S IOF S
KHOLE MILK Per Cent
Water Fat Milk sugar (lactose) Casein Albumin
87.0 3.9 4.9 2.9 0.6
Ash
0.7 ~
Total
100.0
The colloidal particles have not proved quite so amenable to study; they are generally considered to be micelles. Estimates of their molecular weights vary widely, probably because the micelles differ in size under changing environments (4, 7 ) . The micelles contain calcium caseinate, and most evidence indicates that they also contain calcium phosphate, either in a physical complex or as a calcium phosphocaseinate (17, 25). The structure of the casein molecule itself has never been determined although at least three different types, designated alpha, beta, and gamma, have been isolated. It is one of the few proteins containing both sulEur and phosphorus, and it is knonn to be made up of a chain of various amino acids. However, the nature of the linkage betxeen the amino fragments has not been decided beyond question (18). Casein from milk of different mammals varies slightly in composition, but fortunately Norwicxh needs deal only in cow’s milk. Whatever the size or composition of the protein micelles, thcv are easily broken up by heat, acid, alkali, or certain enzymcts, notably rennin. This breaking of the micelles results in the coagulation of the casein, but it also seems to modify the molecules slightly so that there are slight differences between castxins precipitated by various media. Because of these changes prvclipitated casein is said to be denatured. -4fter the fat has been removed from the milk by the centrifuge and the casein has been precipitated, the clear, greenish liquid that remains still contains almost half the milk solids. This is the whey which is so often diecarded or given away for stock feed. Lactose accounts for about 70y0of the whey solids and is in solution with a small percentage of inorganic salts, mostly citrates, lactates, and phosphates. There are proteins dissolved in the whey also. These are the materials from which the whey cheeses are made. They are usuallv lumped into twoclasses,albumin and globulin, although there are known to be more than two t-ypvpes of soluble protein present. Together they amount to about one sixth of the total protein in whole milk. -4lthough whey proteins are commonly referred to as lactalbumin, lactoglobulins comprise
June 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
1259
Casein Coagulating and Drying ( L e f t ) . Initial separation of whey and coagulum i s effected i n draining conveyor a t right on casein machine. Whey decants from reservoir at far end of conveyor. Curd moves countercurrent to wash water i n washing conveyor ( l e f t ) . Casein fines are recovered i n settling tank (lower l e f f ) . ( L e f t C e n t e r ) . Acidified casein is fully coagulated i n this ceramic maze before it drops to draining conveyor.
( R i g h t C e n t e r ) . Iron squeeze rolls (10 X 30 inches) press the wet casein curd against a moving screen composed of 18-inch perforated brass sections. ( R i g h t ) . The casein product is moved from dryer on a screen made of 8 X 96 inch perforated stainless steel panels with slots 3 / 6 4 X 1/a inch.
the largest part of them (11). These lactoglobulins are very important nutritionally and may carry important antibodies. The colostrum produced by all mammals for the first few days after they begin to lactate is high in lactoglobulin. I n fact, it is the principal protein in this milk and may run as high as 8% of the total weight, whereas normal milk seldom contains more than 3.5% of total proteins. However, the law prohibits the sale of colostrum containing milk or the use of such milk in edible products. The remainder of the whey proteins are true lactalbumins. They contain no phosphorus. Their physiological function is not fully known but they are thought to be equally as nutritious as casein. Human milk is exceptionally high in lactalbumin which may account for as much as 50% of the total protein content, but the significance of this variation is unknown. About 6% of the nitrogen in milk is contained in compounds other than casein, globulin, and albumin. This nitrogen is combined in lecithin, certain vitamins, and compounds normally found in the blood
steel, insulated holding tanks. Milk that arrives in tank trucks from outlying collection stations or other Sheffield dairies is usually pumped directly into the holding tanks. The milk is cold when it arrives, and if it is stored the temperature is kept a t or below 40’ F. in accordance with Board of Health regulations. Normally the milk is separated immediately. Before entering the cream separators, the milk is warmed to about 90” F. t o agglomerate the butterfat particles and permit a more complete separation. Four standard, disk-type, solid bowl separators ( 6 E )remove about 8 to 10% of the volume of the milk as high fat cream. The “fat-free” milk or skim milk goes directly to a surge tank feeding the casein machine. It contains 8.5 to 8,87& solids.
Casein The conditions applied in the casein machine vary with the type of product desired (see Table 11). Both the temperature of (10). the precipitation and the amount of acid added have substantial effects on the structure of the curd that will be formed. The PROCESSING curd is larger and firmer at higher temperatures. Increasing the Milk arrives a t the Sheffield plant either in cans or by stainless amount of acid makes the curd more granular and increases the solubility of the salts. Large rubbery curd is difficult to wash steel, 3000- to 4200-gallon tank trucks. Cans are unloaded directly onto a roller conveyor, checked for sweetness by smelling, and tends to retain a higher salt concentration. However, fine and dumped into an unloading tank. The empty cans are placed crumbly curd produces an excessive amount of fines that must be in an automatic, high temperature washer which feeds them out removed from the whey or be lost in the wash water. Hence to onto the loading platform whcre they can be put back on the obtain a very pure product with almost no salt content, low farmer’s truck. The milk feeds continuously from the unloading temperature and high acid are used along with copious washing. vat, either without further cooling directly to the separators or Where a higher salt content is not objectionable and may even after cooling into one of five 5000-gallon glass-lined or stainless be desirable, higher temperatues and lower acid addition may be used. Gross variations in the skim milk t o acid ratio are achieved by altering the rate of skim milk feed by changing the impeller TABLE IT. OPERATING CONDITIONS FOR CASEINCOAGULATION on the skim milk transfer pumD . ~.(11E). . Milk Skim milk coming to the casein maFeed Dried Product Rate, Wash Water ProteinQ H20 Ash chine is heated wit.h warm water in a Gal./ Temp., Gal./ Temp., (Min.), (Max.), (Max.), Acidityb multiple-pass heater (14E). Acid is added Hr. F. min. ’ F. % % % (Max.) in a baffled, vertical tile cylinder. Proper High-nitrogen 2400 110-112 12 85-90 88 8.0 2.1 ’ 0.1 (pH4.8 addition of acid is very important to the min.) h-ew process 3200 110-112 85-90 86 10 2.5 0.35bH4.5 production of a uniform, high quality min.) High-pH 3200 115 None 85-90 85 10 2.75 0.25 (pH4.8 casein. I n the Sheffield unit 3774 murimin.) atic acid is drawn from a rubberITX 6.38. b Titratable acidity calculated as lactic acid. lined storage tank and diluted with water in a stoneware feed tank. From ((
1%
I N D U S T R I i L L A N D EAHIWZJIIE8G C H E M I S T R Y
here it flows into a float controlled w t a n t level tank h u g &a stoneware control valve and into the acidifying cbamlxo: mntml valve is manuslly adjusted to pmduca a curd of the pappearance and feel (Figure1). The bafaed cylinder e n a l @t ~ sll the milk comes quiokly and i n t h a t d y i n oentact with the acid 80 that the casin coagulum formed is of an ~ v e zmn&ency. l
Vol. 44, No. 6
whioh in drained daily and the du& pumped to a aeoond Aftm ssttling, the 6nes from this tank are trsnslerred into the screen-bottomed box. Th? liltrate water from this box is diecsrded. The h e n 8se collected from the box about once a day, mixed with the oversized dried casein from the produot millingseparation to improve their phyeical characterietios, and introduced into the casein
a , rssthng tank (44 X 114 X 24 inohen).
dryer. In spite of thin procedure aome 5 e s am still lost in the waeh water. These loma am great& when high purity product is being made beoause thin curd is less coheaive and more waeh water is used. The pressed curd from the squeeze rolls is picked up by a mnveyor which lifts it to the spreader of a conveyor dryw (##E). The is an Winch trough perforated with '/,-inch holen and equipped with a ribbon-type agitator revolving at 84 r.p.m. The curd at thin point is quite friable and is deposited on the dryer belt in a half-inch granular layer. The drying chamher is divided into t h e 16-foot zones. The material passes thmugh the unit in 80 minutes. The first zone of the dryer at 135O F. is the coolest to avoid forming a bard g l a d surface on the particles which would prevent further drying. Such an undesirable condition is known 88 caephwdening. The next two sones are at about 180' and 155' F., respectively; heating is by steam coils. The casein come8 offthe dryer conveyor with a moisture content of less than 10%. A counterrotating ECRW conveyor at the end of the dryer breaks up the m e i n sheet and diachsrgea to a centrifugal blower @E), which MOIS the'granular product while lifting it to a cyclone separator (34inchen in diameter by 42inches deep). From the cyclone the caeein dmps into a roller mill with
+
,
~~
Figure 1. AEid Feed System for Casein Machine
The mixing cylinder is in one end of a stoneware box fitted with transverse bafaea (Figure 2). In the 15 seconds it taken the curd to paae through this box, the casein precipitation is completed and the spongy maae of curd drops out on a conre screen (Figure 3). A titration is NU on the whey periodically to check the judgment of the operator in adjusting the acid flow. The whey that paeaes through the screen is caught in a tray and drained off for fyrther processing. The fresh curd that falls offthe screen &ill contains about 85% water. From the screen it drop6 into the middle of a %foot ribbon conveyor inclined at 9'. This conveyor kneads and b& the curd 88 it travels upward and allows the whey to drain downward to be combined with the whey from the screen drain tray. When the curd reaches the top of the draining conveyor it contains about 70% water. It drops through a curd brealter, consisting of a 12-inch, troughlike sheet perforated with %inch holes, inches on centers. Rigid amu rotating about a central ahaft at Bo r.p.m. f o m the curd through the perforations. When a higber purity casein is desired a second beater is installed in tandem. This supplementary breaker is 30 inches long and hae '/winch holes on 'fhinch centers. Its agitator is in the shape of a square U attached at either end of the shaft which rotates 100 r.p.m. In the breaker the curd is waehed with a stream of warm water. The curd at thin point is at about 100' F. and the wash water must be heated to avoid chilling the curd which would p & e it hard and cohesive. From the curd breaker the casein dmps into the waf*6lled lower section of another conveyor identical to the draining conveyor. A spray of w a w plays on the top end of this converter, and ae the curd is headed and broken and raked by the conveyer, the wash water diaeolved out the occluded salts. T h e Beoond conveyor discharges a curd with a moisture content of about 65% onto tbe squeeze rolls (9E). Spring tension on the rolls squeeaes another 15% of moisture out of the curd. At 50% moisture the curd feels almost dry and is about 88 d w ae it can be gotten by mechanical means. The water that draim through the screen of the que& rolls is caught in a pan and drained to a box with a 3Gme8h screen on the bottom which eeparak out the oseein fines. The oaaein kea from the whey screen and draining conveyor. also collected in this box, are settled out in a g b l i n e d tank (6 feet by 8 feet by 30
.
Figure 2. B d e B o x for Camin Coagulation
two, nonmeahing corrugated rolls which reduce the casein to 20 to 30 mesh ( f 8 E ) A screen below the mill removea ovemize m ~ terial which ie recycled to the mill or blended with the drained The screen feeds directly to a bagging conveyor. All casein from the roller mill is bagged directly. That which will he further processed into hydrolysates must be shipped t o another plant in Oneonta, N. Y., 30 milen away. 5 e s for drying.
Milk Protein Powder A part of the caeein is processed into a milk protein powder by a reoently developed technique for which a patent han beea a p plied. The product is used primarily as a aupplement in human food pmducte. W h e n this product is to be made the wet caaein from the squeeze rolls is conveyed by a drag conveyor to a hammer mill with a 0.03sinch screen (83E). Water is introduced into the mill, and the resulting slurry (15% solids) is recyded through the mill until all the caeein hss been thoroughly pulverbed. About 1150 pounds of wet curd (50% H90)is fed into the mill in a batch.
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INDUSTRIAL A N D ENGINEBAING CHEMISTRY
lune 1952
Eighteen hundred gallons of akim milk are condeosed t o 1400 pounds of wneentrate (60% solide) in a stainless steel evaporator (67E)and added to the a P d i n g hnk. The mixture in paeteurised at 160' F. for one-hlf hour by a hot water jacket. It in then cooled to 121)~F. and pumped to 8 spray
drums,126 pounds to the drum. An average batch given a yield Of
Pounds.
W u m and potassium *+ten are made by a similar p r w 088. A amdl amount of canem is e dwith m e w 0 1 to remove all traoe vitamins.' This devitaminiaed casein ia used p& m d y as a control for dietary studies.
dryer ( B E ) . The liquid going into the dryer haa a solids content of abwt 24%. The powdered product contains 2.5 to 3.0% moisture. The average batch producea la00 pounda of milk protein powder which in screened through a 2 3 m d screw and packed immediately in fiber drums.
l26l
w h e y Protein0
The whey tbat o v e d o w ~from the whey settling tank, containing 6.2 to 6.4% of lactoae, whey proteins, and inorganic salts in
Caminate I .
A smsll amount of casein in takw from the s ~ u e e s e mns and processed to alkali metal caneinaten. To m+ calcium oaaeinste, high urity c u d in mined m t h chilled water to very amafparticles ( B E ) . It in sometimes necessary to recycle the casem thmugh the miil several times before the particle s h e is uniformly smdl. Calcium hydmxide does not react m m l with casein, and if large curd perticlea are leg ,in the cbarpre they will carry through the neutrallaation without reacting. Chilled water must be used to hold the h p e r a t u r e in MOWBo' F. Without cooling, the fricthe "1 tion ~nthe mill would raise the temperature to 80" F. or higher and encourage bacterial and mym~activity. Batch charge is 2868 pound0 of wet C& and 8M)gallons of chilled Water. The thin slurry is pumped to a treating hnk and 40 pounds of calcium hydmxide and enough adfitions1 water to make 1220 gallons are added. After thorough m i x i i without hating, the pH of the batch in determined and more lime added if necessary to bring the batch to neutral pH. The
I E W cO""rv0R
Figure 3.
Sheffield Automatic Casein Machine
neutral mixture is heated t o 145O.F. and beld
at that .temperature for 1 hour mth continued agitation. After t h m paateurisaticm is complete the batch is allowed to cool to laOD F. and in held at that temperature for spray Other caseinates can be pastqurised at higher tempem
they are leas heat nermtive. The 12% calcium csseinate solution is spray-dried to 2.6 to 3.0% mont- at sn exhaust temperature of 1800F M E ) The product is sifted thmugh a 2O.mesh m w m d ed III : fibber %%oawe
pumped into a t m t i n g tank (Figure 4). The n a t step in its P r o c e n g depends on the type of whey pmteins tbat are desired. If pure protein is deaired the whey is brought to a boil by the direet intmduction of ateam at 125 pounds per square inch for 20 to 30 &uteS. At the acidity of the untreatsd whey (pH 4.6) the protein begins to coagulate at about 145' F. and is almost cornpletely precipitated at the boiling point. The precipitate contains about two thirds of the nitmgen content of the whey. The nitmgen thst is not precipitated in primarily combined in nonprotein compounds. This isoelectric, ooagulated hrctalbumin is 75 to So% protein and cont a i n ~ 5 to 7% ash. Nearly the entire production &tNorwich is hydrolysed into nutrient products at Sheffield's Oneonta plant. Moat whey pmteios are recovered as calcium salts by adding lime to the whey tank. The lime is made up roughly into a 10 to 20% slurry in a black iron feed tank and added to the whey until the pH is 6.8 ea determined by titration. Experienced operators can estimate the proper pH of the hatch from the uppenmace of the curd 80 that only a few titrations need be made. The limed whey is brought to a boil by the introduation of steam to complete the precipitation. Liming bringn down about 75%af the total nitmgen in the whey. The remainder is
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I N D U S T R I A L A N D E N G I N B,ER I N G C H E M I S T R Y
Vol. 44. No. 6
June 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
stituents include most of the inorganic salts present in the original milk. However, most of these salts have dietary value, and since this material is intended for use in animal feed formulation their presence is not objectionable. After the precipitation of either isoelectric or limed lactalbumin the batch is allowed to cool and settle for 15 to 20 minutes, and the liquor is decanted off and pumped to a plate-and-frame filter press (69E)which uses diatomaceous earth as a filter-aid on duck cloths. The filtrate, a clear sugar liquor, goes t o the lactose recovery unit. The sludge from the bottom of the tank then follows the clear liquor through the filter press, the filtrate going t o the lactose department. If the cake is isoelectric protein it is removed from the press and tray-dried t o about 5% moisture content in a tunnel dryer (2823). The dryer is held a t 165' F. and requires 12 to 14 hours to bring the product to the desired dryness. The dried produrt is hammer-milled using a 0.038 screen (%$E)and bagged immediately for sale or shipment, to the hydrolyzate plant. When calcium lactalbuminate is made the filter cake is fed to a mixing screw conveyor where it is joined by exhausted mother liquor and wash waters from the sugar crystallizers which have been concentrated to 60 to 65oJ, solids in a stainless steel evaporator (27E). The resulting slurry is too fluid for treatment in a rotary .dryer and is mixed with five to six times its weight of recycled, dried product. The mixer discharges into the inlet of a concurrent type rotary dryer (8E). The air to the dryer is heated by direct contact with the heating oil flame so that the stack gases also pass through the cylinder. The dryer cylinder is amply fitted with lifting baffles so that the powder is repeatedly dropped through the hot gascs. The gases enter the horizontal cylinder a t about 700" F. and arc exhausted at about 200" F. The dried product is about 25% lactose, 33% protein salt, and as much as 30% ash; moisture is 5%, and inerts, primarily filteraid, 4%. The dried product is sized in a hammer mill ( W E ) using a 0.038-inch screen. Exhaust gases from the dryer pass through a rotary classifier ( 1 E ) which returns entrained solids to the product line and discharges the gases to the atmosphere. -4gyratory sifter separates the sugar-protein-milk salt feed mixture into coarse and rcgular grades for packing in paper bags. Milk Sugar The filtered, deproteinated whcy from the albumin precipitating tank goes to the milk sugar operation (Figure 4). The first step in the treating of the liquor is to concentrate it to about 40% solids in a Rtainless steel, triple-effect evaporator (12E). The crude sirup from the evaporators is placed in one of two 8000-gallon (8 X 15 X 9 feet) stainless steel, holding tanks. The sirup is allowed t o stand overnight and then is heated by direct steam injection prior to filtration through a resin covered filter press ( d 9 E ) using a diatomaccous earth precoat on duck filter cloth. The filtrate is further conccntrated t o about 60% solids in a single-effect, finishing evaporator, identical to the individual effects of the primary evaporator ( 1 S E ) . The resulting thick sirup is pumped to jackcted crystallizers (31E), where cooling water reduces the temperature t o 50 to 55" F. This treatment precipitates bcttcr than 60% of the lactosr in very small crystals. At the end of the crystallizing period the slurry of sirup and crystals is dropped by gravity from the crystallizers into a perforated-basket type centrifuge (16E). The centrifuge reduces the moisture content of the crystals t o 7 to 10%. Nozzles inside the centrifuge baskct wash the lactose crystals continuously with clear Rater. The operator watches the effluent from the centrifuge through a look box and continues the operation until the wash water runs white and clear. The quantity of wash water used with any specific batch of crystals will vary depending on the nature of the whey being pocessed and t o a lesser extent on the
I263
conditions of crystallization. Casein whey from fresh milk usually produces relatively large, well-formed sugar crystals that wash with minimum effort, Wheys, soured b y fermentation, often produce small, sticky crystals which are very difficult t o wash free of mother liquor. An average batch requires 1.5t o 2.0 pounds of wash water per pound of sugar crystals. The mother liquor and wash water from the first crystallization are returned t o the single-effect evaporator where the solids content is raised back to 65% and then returned t o the crystallizers. Crystallization of the second run crystals follows a cycle similar to that of the first run product. The wash water from the centrifuge in this step contains about 24% solids but only 7% lactose. This wash water is combined with the spent mother liquor to give a sirup containing about 3oy0 solids which is sent t o the feed supplement operation where it is combined with calcium lactalbuminate and dried. Less than one quarter as much crude lactose is obtained from the second crystallization as from the first. The crystals are higher in ash and protein and are not suitable for a commercial product. Protein content may be as high as 4y0, which gives the crystals a dark color, and ash, mostly calcium phosphate with some calcium lactate, may run up to 10%. Furthermore, the crystals are tacky and almost impossible to dry in conventional equipment. Actually almost all these calcium salts could be r e moved in the pre-evaporator heating by raising the pH at that point, but such treatment would produce a darker colored sirup and make the ultimate decolorizing of the lactose more difficult. The second run crystals are utilized by recycling them t o the thin sirup holding tanks. In the two crystallizations about 65y0 of the total lactose present is recovered. The remaining 35% ends up in the feed supplement. The crude crystals from the first crystallization may be dried directly t o produce "crude lactose" (Table 111). In this case the wet crystals from the centrifuge are dropped through the bottom of the basket directly t o a 16-foot concurrent rotary dryer (18E). The crystals coming out of the dryer are conveyed directly to a feed hopper which serves a simple bagging device. No milling is necessary because the product is in the form of small crystals most of which are less than 60-mesh size.
TABLE 111. LACTOSESPECIFICATIONS Hi0
Ash
(Max.), (Max.), % %
Protein (Max.),
Laotose (Min.),
0.75
97.5
.....
%
%
Size
Crude
0.5
0.75
U.S.P.
0.1
0.1
None
99.5
1007 through
Edible
0.15
0.25
0.25
98.5
100% through 80 mesh
80'rnesh
Relined Lactose. If high purity lactose is desired the crude crystals must be recrystallized. At Norwich refined lactose is made by redissolving the crude crystals in mother liquor from the refined lactose crystallization t o give a solution with a solids content of 30 to 4Oy0 (15" to 20" Be.). The solution is made in a 185O-gallon, glass-lined tank, equipped with a steam jacket (Figure 4). A 24-inch impeller mounted 12 inches off-center and revolving at 90 r.p.m. provides agitation in this tank. All equipment in the refined product operation from this point on is made of stainless steel or other corrosion-resistant material. The lactose sirup is given a two-stage, countercurrent treatment with activated carbon. Carbon is added t o a second stainless steel tank identical with the dissolving tank. This is the finishing stage of the carbon treatment. Carbon that has been used for one batch in this stage is recovered in a resin-coated ( 2 E ) plate-and-frame filter using a diatomaceous earth precoat on duck cloths and added t o the dissolving tank for the initial clarification. Carbon from the dissolving tank is filtered out and discarded. The filtered sirup from the second stage of the carbon treatment is polished through padded filter paper backed by an asbcs-
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
1265
However, Binoe no hydmlyaates for parenteral injection rue produced i t is not ll~oe8881yto keep the equipment T Y PAtub-ih ~ ~ % Hydmly.Total Amino free of antigens. x u Protan Agent HtO Ni Nz Aeb NaC1 PH* When casein hvdrolvsates are to he . . N-ZCC& nvpSin 3.5 12.7 6.1 5.9 1.1 7.2 ' made, new process casein is used as a N-2 Amine raw material. Since Oneonta does not Type E bein T W P ~ 3.0 12.7 4.6 6.2 1.2 7.3 TypeA CaMin Panoray 8 . 1 12.8 6.8 5.2 1.0 6.6 make casein it is drawn from Norwich panorm 3.5 11.7 5.0 . 6.9 0 . 8 e.9-7.2 (hein c.ssin HCI 3-4 8.0-8.1 5.54.8 38.5 30.5 5.74.1 or any one of three other casein plants 4.0 11.8 NutricotL-1 hotelbwnin Pan5.8 8.8 0 .6 0.4 and trucked to Oneonta in 80-pound 12.0 7.0 4.8 1.5 6.8 E&& lsctalburnin Panorm 4,7 paper bags. The win is charged to an * 2% solution at 25- C. agitated digestion tank and slurried with 100' to 120' F. wak. The usual casein chargeis a b u t 5MX)pounds. Ten m large 5OOO-gallon gln~dined, d tern (ZOE)are available 88 well as two similss 25oogallon tos mat in a single diaphragm-type filter (27E). The filtrate vaaaela (WB) for d l e r batches. The w i n slurry is held at from this treatment is bright clear with a slight yellow cast. The clarified sirup is concentrated to a b u t 65 to 70% solids (30' temperature by circulating controlled temperature water im the jacket. to 85" Be.)in a stainlees steel Single-efIeCt evaporator of the same An alkali slurry is prepared in a stainless steel mske-up tsnk design as the finishing cvaporator used in the crude sugar operaand added to the dige&er to eolubilise theprotein. Several elk& tions. The recrystallizing procedure follows the w e cycle that wm lies may he used including soda ash, caustic soda, caustic potasb. used in the initial crystallization, but the crystallisera for the reor ammonia depending on the product being made. Su&ienk fined sugar are shorter and deeper than the crude crystallizer8 and alkali is added to make the medium slightly alkaline. Thia BIB COnstNoted Of StShleaS S h l (82E). brings about complete solution of the protein and near opt& The centrifuging (213E) and washing procedures are also the conditions for the activity of the proteolytic enzymes. As the w e for the relined crptals, although leas wash water (1.0 to 1.5 digeationproceeds the pH drops to about 6.8. Most of this dmp pounds per pound of sugar) is required. The liquor and wash occum in the first 12 h o w . After the alkali slurry has been added to the digeater the water from the centrifuging of the refined sugar is used to diasolve the crude so that the uncryatallised sugar is not lost. Howtemperatureof the charge is raised to 165' F. by the water jacket ever, ash constituents build up in this recycled solvent so that at and held for at least 1 hour. Heat treatment serves to control hactmid growth and destroys undesirable ensymw and bnoteria regular intervals the effluentis recycled to the deproteinised whey coming to the sugar department, and fresh water is introduced so that only the desired type of hydrolyais will occur in the digestion. into the refined m e r operation. The &ed lactose is U.S.P. quality (Table 111) with more Lactalbumin hydmlyzates are made by the eame plooedure as the win products. The only pmcees difference is in ! & tpmnthan 69.5% sugar. It is often 88 much as 99.9% pure. The impurities are largely ash constituents. It is then dried in the rotsrv drver (28E) a t 140' F. outlet temperature. Fr&n the dryer it is picked up by a blower and carried to a mill ($.YE) for aizing. Claeaification is accomplished in a gyratory sifter ( B E ) . Pure lactose in used largely in food and drug preparations where the sise is important for appearance and texture. The lineat grade is labeled U.S.P. Impalpable and is 100% through I20 mesh and a h t 89% through 200 mesh. Most tablet manufactureraprefer the U.S.P.grade, ~ h i c his 100% through 80 mesh. A cormer grade is ueually w d by f w d product formulatom. gram.
TABLE IV. PBOTEINHYDBOLYZA~;~
PROTEIN AYDBOLYWTES
Most of the caesin produced at Norwich is sold directly, but some of the product is further p m ~ ~ at e danother S M d d plant at nearby Oneonta, N. Y. The Oneonta plant was built during World War I1 to make milk protein hydrolysates (Figure 6) to be used as nutrients in commercial bulk fermentations. Since then it has expanded its mope. and produces eeveral other types of protein hydrolysates and microbiological nutrients (Table IV).
PROTEIN
F i m 5. production of Pmtein Hydmlyzatsr, at Olrcontn, N. Y., Plant of She6ield F-s C h s m i d Divieiom
CASEIN HKDROLYWTES
Before beginning a batch of hydrolysates all PMCW equipment must be steam sterilized to destroy any residual b teria or active enzymes that might induce fermentation or destructive hydrolysis. An a result of these precautions the hydmlysata producta contain lesa then l0,oOO orgsnisms per
Perahre of the heat treatment. These are DasteUrised at a hieher &peraturebecausethey aremoredi5ntlt'to di6perse, and c o k + quently it is more di5ntlt to ensure destruction of bacteria in the protein. hving the heat treatment a proteolytic enayme duny is prapared in a Btainlaes steel makeup tank. The composition ofthis nlurry is not measured. It is simply made up to an egsily handled
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
pi-
6. Ch-ids
ew?sistency. Any one of several enzymes can he used depending on the product desired. The Oneonta plant can use trypsin, papain, pancreas gland, or fungalor bacterial enzymes. The proportion of enzyme u d will vary with the degree of hydrolysis desired. Chloroform and toluene are added to the ensyme mixture to inhibit bacterial growth. The type of splitting that occurs with any given proteolytic enzyme is not too well understood. It is possible to follow the degree of splitting by measuring liberated amino nitrogen but not readiiy possible to follow the type or quality of splitting that occurs. For oral use, where a wurce of mixed amino acids is desired, the amino nitrogen c o m p W at least 60% of the totd nitrogen in the hydrolysate. For bacterial nutrients the amount of splitting is variable. A range of amino nitrogen to total nitrogen of 15 to 80% may he in order. At the end of the hour of heat treatment the charge is cooled to the digestion temperature (100" to 120" F.) and the enzyme slurry is intmduoed. The digester is then sealed with a rubbergaeketed cover and the digeation begins. Top-entering, horiaontal stirrers rotating at 12 r.p.m. provide agitation throughout the procens on the large digesters. The smaller vensels have sideentering, propeller agitators. The digestion takes place at a fixed temperature maintained by the water jaoket. The digeg tion temperature depends on the type of enzyme used and type of protein being digested. The digeation time isdetermined by the degree of digestion deaired, the enzyme coneentration, protein concentration, temperature, and pH. Each p d u c t or variation in type of product requires a dserent set of digeation conditions. A o o o d i to chemical analysis most of the digestion of casein is completed after 48 hours. Additional time may be re @red to facilitate filtration and decoloriaing. A t the end of d w t i o n the tank is opened and adsorbents or clarifying agents are added equal to about 1% of the weight of the casein charge. The hydrolyzate is pumped through a single-pass tubular heat exchanger at 170' to 180' F. (7E)to soluhilire the amino acids, then through a plate-and-frame filter press (JOE) at about 12 gallons per minute, and finally through a plate-type heater (.%E) for Rash pasteurization. The cake reaulting from this filtration contsins about 10% of the solids charged to the digester. These solids are insoluble amino acids and insohhle enzyme residues.
Vol. 44, No. 6
from Milk
TYROSIN PRODUCTION
Pure tymdn, one of the amino acids, may be recovered from the hydrolyain liquor. In this recovery process the freehly digeeted liquor passes thmugh a stainless steel settling tank equipped with bottom weirs. The tyrosin crystals settle out, and the liquor is returned to another digester and proceaeed by the mal procedure. After the liquor has been drawn off, the tyrosin crystals are washed with water to remove &dual hydrolyzate~. After draining they are tray-dried at 150' F. with 27 inches of merrmry vacuum. Recovery of the solid hydmlyzatea from the digest is accomplished by concentrating the wlution to 55 to So% solids in a small, single-effect evaporator (SE), operating at 135" to 140'F. and then spray-drying the heavy solution. The spray dryer (4E) is a stainleas steel, horizontal type and atomiaes the stream at 2500 pounds per aquare inch gage. It has an e5cient multiple cyclone dust collecting system,which permits easy cleaning and rapid change-over from one type of product to another The hydrolysates are light cream-colored, grmulsr materials containing 2 to 4% moisture. They paae 100% through 140 mesh and are packaged in fiber d r u m without milling. Most enzyme hydrolyzates made by She5eld are produced by this process. T h e time cycle is essentially the m e in all cases although the aolids content of the digestion mixture may vary, and the amount of enzyme added is adjusted to control the deof hydrolyain of the hished product. Both trypsin and pancreas are used t o hydrolyze casein. Casein is also hydrolyfied with hydrochloric acid to produce Hy-Case, a food Eavoring agent. The acid hydrolysis process at Norwich has been extensively revised, and new equipment was being instslled when this article wa4 in preparation. PACKAGMG
The products of the Norwich plant are shipped in multiply moisture barrier bags or fiber drums, with and without polyethylene liners. The protein hydrolyzates produced at Oneonta present a more complex problem because of their extremely hygroscopic nature. At present all these products are packed in 41-gallon fiber drums with an aephalt moisture harrier. However, a newly developed type of Hy-Caae is even more sensitive to moisture than the pre-
June 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
1267
vious products, and it neccssitates the additional use of polyethylene liners in the drums. UTILITIES
-4central steam plant and city power lines supply the Sheffield chemical plants. Hot water for process use is made by direct steam injection at the point of use a t Norwich. Oneonta has a central water heater. Cooling water is drawn from the nearby river and used without treatment during most of the year. However, during the four summer months this water is too warm for efficient operation and must be replaced by ground water drawn from wells on the plant site. Used cooling water is usually returned to the stream. Process water is alwavs taken from the wells.
.
MATERIALS OF CONSTRUCTION
Several persistent, if not acute, corrosion problems are encountered in milk by-product recovery. The milk whey itself is mildly corrosive because of the ever-present slight concentration of lactic acid. I n addition corrosion problems are intensified by the addition of hydrochloric acid in processing casein and the accumulation of salts during the processing of lactose. Wherever possible, stainless steel is being substituted for copper and ordinary steel construction. Pump corrosion in the transfer of lime slurries is avoided by using steam eductor lifts for this purpose. I n the sugar plant the problem is more one of preventing contamination of the product than protecting the equipment. The evaporators are made of Type 304 stainless steel throughout, and all equipment and piping used in the production of the refined sugar is of the same material. The plates and frames of the filters in the sugar plant are coated n ith a baked phenolic resin sprayed on in multiple layers over a freshly sandblasted surface. This equipment has given good service. The frames are invariably the first to fail, but they last on an average of 4 years without recoating. The centrifuge bowls for the crude sugar recovery are of bronze, but the refined sugar centrifuge is of stainless. The lines in refined sugar operation which must carry slurries containing carbon are of rubber-lined pipe. These slurries are moved by Duriron pumps. Glass pipe is used for the transportation of hydrochloric acid to the casein machine. Solutions of protein hydrolyzates are particularly corrosive. As one operating man put it they turn a welded joint into a sponge in no time. Consequently the Oneonta plant is constructed of neldless stainless steel pipe and fittings and glass-lined and stainless steel vessels. The Sheffield chemical products plants have carried over from the dairy industry the practice of using so-called “sanitary piping.” This type of piping is made with all quick-opening, screwed connections so that it may be disassembled and cleanedscveral times a day if necessary. Sheffield takes advantage of this equipment to prevent bacteriological and enzyme contamination of their process streams.
Aluminum Plate-and-Frame Filter Solutions of protein hydrolyzates present particular corrosion prohlems because of their acidic nature. Sheffield overcomes this difficulty i n its filtering operations by using plates and frames made completely of aluminum.
fied caseins now under development are expected t o re-establishmilk proteins in the adhesive field where casein once held a strong position. Sodium caseinate is used in various food products where an edible emulsifier and stabilizer is required and in the formulation of some pharmaceuticals and baby foods. It is also of importance as a protein fortifying agent because of its high concentration of available proteins. Calcium caseinate, also a high protein product of edible quality and also a source of dietary calcium, is important as a fortifying agent in the preparation of foods for special diets. Sheffield Milk Protein has been found to be a highly satisfactory supplementary source of protein in the preparation of baby cereals and other food and pharmaceutical items. The hydrolyzates, Edamin and N-Z-Amine Type A, have already found their place in the field of pharmaceuticals where, an enzymatic hydrolyzate of high biological value is required. N-%Amine Type B and N-%Amine Type E are used as bacterial nutrients in the bulk fermentation field along with Nutrient Ll. These same hydrolyzates are also being found useful in the cultivation of special cultures such as those which produce tetanus toxin. N-%Case has proved most satisfactory for this application. The acid hydrolyzates are far superior t o the enzymatic hydrolyzates of casein in the food flavoring field. A high content of monosodium glutamate plus a unique meaty flavor is winning them acceptance in the flavoring of soups, gravies, meats, and boullions. What Next?
PRESENT MARKETS
The largcet volume product from the Xorwich plant is lactose. It has a fairly stable market in medicinal capsule formulations and as a carbohydrate source in food products. It is also used as a nutrient in penicillin fermentations. Caseins (Figure 6) presently find their widest use in the paper coating field and to a smaller degree in the stabilization of rubber latex emulsions. They also have outlets in the pharmaceutical fields and in the formulation of special diets for animals, for instance in mink diets where a protein of high quality is required. Edible grade casein is finding increased application in bakery products and other special grades will find a wider use in pharmaceuticals and in the stabilization of rubber-base paints. Modi-
Increasing costs of milk, in addition to the seasonality of the supply, make it imperative that improvements continue to be made in processes and products at Norwich. Better recovery of fines in the casein operations, continuous methods for complete removal of whey proteins, and still better recovery methods for lactose are being studied to reduce costs. At Oneonta. pressure type acid hydrolysis equipment is being installed to replace atmospheric equipment. The Oneonta spray dryer is being modified to include a “wet scrubber” in addition t o the present dry prochct recovery system to attain still better product recovery. This change will permit use of the spray dryer on a greater range of products, some of which would otherwise cause difficulty in dust collection.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Research and development work is directed at completely new products a s well as modified forms of existing products. T h e p r o g r a m is n o t limited t o milk o r whey as raw materials. Attent i o n is being given t o t h e development of products t h a t can be produced during periods of reduced milk supplies. Such product i o n would make possible better a n d fuller use of equipment a n d manpower a n d give a greater dollar r e t u r n o n t h e invested capital. I n t h e fermentation n u t r i e n t field, Sheffield is diversifying i t s main line of enzymatic and acid hgdrolyxates of milk protein to include items such as peptonized powdered milk, Milk N u t r i e n t L-H ( a product wherein t h e lactose has been enzymatically split i n t o t h e simple sugars, glucose, a n d galactose), a n d soy meal peptone, produced by t h e papaic digestion of soy proteins. A similar diversification program o n lactose is under way. Nelv lactose derivativcs such a s galactose, lactobionic acid, a n d “lactositol” are being developed. These items h a v e been t a k e n f r o m t h e near rare a n d rare chemical elasses. Lactobionic acid is now being introduced t o t h e chemical a n d pharmaceutical trades a n d semiplant scale production is anticipated during t h e current summer period. Galactose has indicated uses i n t h e food a n d pharmaceutical field a n d in t h e formulation of dentifrices. It is possible that as t h i s product becomes cheaper through larger use a n d production it ~’iillalso find markets in t h e fermentation field. Lactobionic acid has m a n y interesting properties. Its most probable uses will be as a sequestrant o r emulsifying agent in the food, pharmaceutical, and industrial chemical fields. It is also suggested as a solubilizing agent for pharmaceuticals. T h e fact t h a t stable solutions of calcium lactobionate can b e m a d e a s high as 70y0 by weight solids suggests its use in t h e veterinary and medicinal fields as a highly concentrated source of organic calcium. Although n o t discussed in t h i s article, Sheffield h a s pioneered a group of lactate salts, produced b y the fermentation of t h e lactose in whey t o lactic acid. Calcium, sodium, potassium, magnesium, ferric, a n d copper lactates are made along Kith lactic acid. Continuous fermentation methods a r e being studied.
REFERENCES
.
L., Colloid J . (USSR), (1) Bilenski, F. A., and Kastorskayu, 2, 193-6 (1936). ( 2 ) Burk, N. F., and Greenberg, D. N., J . Biol. Chenz., 87, 197’ 238 (1930). (3) Carpenter, D . C., J . Am. Chem. SOC.,53, 1812-26 (1931). (4) Ibid., 57, 129-31 (1935). ( 5 ) Chappell, F. L., U. S.Patent 1,892,233 (Dec. 27, 1932). (6) I b i d . , 1,992,002 (Feb. 19, 1935). (7) Ford, T. F., and Ramsdell, G. A , Proc. 12th Intern. Dairy Congr., 2 , 17-26 (1949). (8) Hand, D. B., Brereton. J. G., and Xaufmann, O., U. S.Patent 2,489,880 (Nov. 29, 1949). (9) Hartford, C. G., U.,% Patent 2,209,694 (July 30, 1940). (10) Herrington, B. L., Milk and Milk Processing,” p. 116, New York, McGraw-Hill Book Co., IIIC..1948. (11) McMeekin, T . L., J.M i l k a n d Food Technol., 15, 57-61 (1952). (12) Milk Industry Foundation, Washington, D. C., “Milk Facts,” 1951. (13) Pyne, G. T., J . F g r . Sci., 19, 403 (1929). (14) Rogers, L. h., Fundamentals of Dairy Science,” 2nd ed., p. 128, New York, Reinhold Publishing Co., 1935. (15) Sheffield, IT. H . , U. S. Patent 1,716,799 (June 11, 1929). (16) Smith, J. R., Jr., IND.ENG.CHEW.,2 6 , 819-22 (1934). (17) Sutermeister, E., and Browne, F. L., “Casein and Its Industrial Applications,” pp. 13-14, Ken, York, Reinhold Publishing Co., 1939. (18) Ibid., pp. 35-61. (19) Svedberg, T., Carpenter, L. XI., and Carpenter, D. C., J . Am. Chem. Soc., 52, 241-52, 701-10 (1930). (20) U. S. Dept. of Commerce, Business Statistics, Statistical Supplement to Survey of Current Business, 132 (1951). (21) Ibid.. p. 166. (22) Van Slyke, L. L., and Baker, J. C., J . B.i’ol. Chem., 40, 345 (1919). (23) Van Slyke, L. L., and Bosworth, A. V., Ibid., 20, 135 (1915). (24) Whittier, E. O., and Webb, B. H., “By-Products from Milk,” p. 2, New York, Reinhold Publishing Co,, 1950.
Vol. 44, No. 6
Processing Equipment (1E) American Air Filter Co., Inc., Louisville, Ky., Roto-Clone, Type D wit,h No. 16 skimmer precleaner, bclt driven by 15-hp., 1750-r.p.m. motor. (2E) Bishopric Products Co., Inc., Cincinnati, O . , Lastiglas, thermosetting, phenol-formaldehyde coating. (3E) Blaw Knox CO., Buffalo, N. Y . , Buflovak Equipment Division, single-effect, rapid circulation evaporator, 4000 lb. evaporation per hour. (4E) Buflovak Midwest Co., Mora, Minn., Buflovak No. 650, horizontal spray dryer, 900 lb. water/hour with inlet air 10,000 cu. ft./min. a t stand. temp. and press. and 340° F. Outlet air, 170’ F., four nozzles. (5E) Clarage Fan Co., Kalamazoo, Mich., Type C , No. 8 fan, 3600 r.p.m., direct drive from 2-hp. motor. (6E) DeLaval Separator Co., Poughkeepsie, S . Y., Y o . 192, DeFava1 disk-type centrifuges, cap. 11,000 lb./hour. (7E) Foster Wheeler Corp., S e w York, K. P., single pass, stainless steel heat exchanger with j/s-inch tubes and 11.8 sq. Et. heating surface. (8E) General American Transportation Co., Chicago, Ill., Louisville H-dryer, 48 inches X 30 ft. direct heat, oil-fired rotary dryer, cap. 1250 lb./hour from 70 to 6 % moisture. (9E) Ibid., Louisville four-roll dewaterer, 0.033-inch perforated screen moving 1 ft./min. (10E)Glascote Products, Inc., Cleveland. 0.. 5000-gal., glass-lined tank, with 7-hp.. 5-ft. diameter top-entering agitator. (11E) Grove Regulator Co., Oakland, Calif., Type BH, Flcxflo Sanitary centrifugal pump, interchangeable impellers, from 3 7 / ~to 45lginches diam., cap. 2600-3500 gal./hour. (12E) Henszey Co., Watertown, Wis., Henszey Model 198-11/*-12, stainless steel triple-effect evaporator, cap. 25,000 Ib. water/ hour when condensing 6% solution to 40%, 13, 17, 25-26 inches Hg vacuum. (13E) I b i d . , Model 150-11/2-12, stniiiless steel finishing nans. 6000 lb. evaporation per hour, 22-26 inches Hg vacuum. (14E) Ibid., 26-pass sanitary stainless steel preheater with 52-1I / * inch tubes or 204 sq. ft. heating surface. (l5E) Hepworth Machinery Co., Inc., Long Island City. Ii. Y., centrifuges, baskets 40 X 24 inches deep, 600 or 1200 r.p.m., 0.032-inch perforated screen, steel-bronze construction. (16E) Ibid., Type 304, stainless steel basket. (17E) Infilco, Inc., Tuscon, Ariz., international disk filter, size 5 , 600 gal./hr. a t 15 lb./sq. inch, stainless steel construction, (18E) Link-Belt Co., Chicago, Ill., Roto-Louvre dryer, KO. 310-16, 16 feet long, cap. 2000 lb.,’hour sugar from 10 to 0.03% moisture, internal construction Type 304 stainless steel, steam heated. (19E) Mercer-Robinson Co., New York, N. Y., Unique Roller i\lill 9 X 24 inch rolls. (20E) Pfaudler Co., The, Rochester, N. Y., 2500-gal., glass-lined, jacketed kettle, equipped with side-entering agitator. ( 2 l E ) Porter, H . X., Co., Inc., Pittsburgh, Pa., crystallizers, cap. 1137 gal., 3I/z i t . wide X 4 f t . deep X 12 f t . long, singleribbon agitator a t 1 r.p.m. (22E) Proctor-Schwartz, Philadelphia, Pa., seven-unit automatic conveyor dryer, cap. 700 lb. CDWB/hour from 1227, BDWB to 9.9% moisture BDWB. (23E) Pulverizing Machinery Co., Summit, N. J., No. 3 T H Mikro Pulverizer, 4700 r.p.m., 2000 Ib./hr. a t 80 mesh (0.0270.125 inch screen), stainless steel construction. (24E) Ibid., No. 2 DH Mikro-Pulverizer, standard construction. (25E) Richmond Manufacturing Co., Lookport, N. Y., Niagara Whip Sifter, Size 10A, KO.F-26-3/a-8, stainless steel throughout. (26E) Rogers, C. E., Co., Detroit, Mich., modified Rogers four-head dryer, cap. 1200 lb./hour, with nozzles a t 2500 lb./sq. inch gage, 16 No. 69 nozzles, 21 core, dryer air 15,000-18,000 cu. ft./min. a t stand. temp. and press. (27E) Ibid., 6-Et. diam., Type 304, stainless steel vacuum pan, sanitary construction, five horizontal coils, 6000-10,000 lb. evaporation per hour. (28E) Sheffield Farms, shop-fabricated warm air kiln, four tunnels, 32 X GO X 184 inches, 2000-3000 cu. ft./min. per tunnel, entrance temp., 120-180’ F. (29E) Sperry, D. R., 8z Co., Batavia, Ill., 30-inch plate-and-frame filter press, plastic coated, 34 chambers. (30E) Ibid., cast aluminum plates and frames. (31E) Swenson Evaporator Co., Harvey, Ill., Swenson-Walker crystallizers. (32E) Walker-Wallace, Buffalo, N. Y., Type H T , KO.361, stainless steel plate heater. RECEIVED for review hIay 13, 1952.
ACCEPTED May 18, 1952.
