FUSED TRICALCIUM PHOSPHATE FERTILIZER Possible Animal Feed Supplement D. E. WILLI-AMs, F. L. J l c L E O D , ELISE AIORRELL, .iKD F. P. JOKES The Unicersity of Tennessee Agricultural Experiment Station, Knoxnille, T e n n .
T
HE war period supply
fed 3% phosphatic limeExperinients described in this paper were designed to of bone men1 and other stone, which furnished a distinguish between the physiological aiailahility of the suitable phosphate carriers total of 0.037, (300 p.p.m.1 component phosphorus in a TVA fused tricalcium phosfluorine in the diet, conhas brcn reportcd as less phate and the toxicity of the unrenioied fluorine. Growth, tinued to reproduce and rear than the estimated requirestorage of phosphorus in white rata, and reproduction their young from five matmentsfor domestic livestock through seieral generations were the criteria. When ings as satisfactorily as did feeding (6). Stimulated by fused tricalcium phosphate of no more than 0.3% fluorine the need for new aources of a group receiving ground content was fed to the animals over a 90-day period as p h o s p h o r u s in livestock limestone. 1% of their diet, to proiide a total phosphorus level of Freser et al. (3)found that feeding, workers a t The Uni0 . 2 7 ~they ~ showed normal growth and phosphorus retena high proportion of the versity of Tennessee have tion. AIeasured by reproduction through the fourth generbeen studying the nutriphosphorus and calcium of ation, the fused phosphate, fed in a diet with a total phont>ional utility of fused triseveral fused phosphates, phorus level of 0.40J,, proved75 to 93y0as effective as a standcalcium p h o s p h a t e , t h e containing 0.05 and 0.22% ard material of established phosphorus-feeding value. Tennessee Valley Authority fluorine, was available for product intended for soil the nutrition of the rat; but fertilization. This m a t e their experiments were not designed to test the toxicity of the material. rial, which carries not more than 0.4‘1; fluorine, is the result Barrentine, Maynard, and Loosli ( 1 ) found that B thermally of a thermal process by which the fluorapatite of the raw rock defluorinated phosphate was slightly less efficacious than their is decomposed and 8570 or more of the component fluorine is expelled. The molten draw is quenched and sized to specificacalcium phosphate control, a t very low levels. When this defluorition. Complete expulsion of fluorine is deemed unnecessary, nated product was used t o raise the phosphorus content of t h e and possibly not desirable, when the fused tricalcium phosphate diet t o 0.50Yo or more, the phosphate was as effective as the is to be used as a fertilizer ( 7 ) . If the phosphorus of this calcium phosphate in the formation of bone. product proves effective as a nutritional supplement, the quesEllis et al. (a) rate a sample of fused tricalcium phosphate “very tion arises as t o how much fluorine can be allon.ed in the product good”. or 80% as effective as bone meal in animal feeding tests without attendant menace to normal growth and reproduction. carried out by four collaborating laboratories. The new product has been designated and defined as “fused triThe present experiments were designed to test the suitability calcium phosphate, a product composed chiefly of the alpha form of fused tricalcium phosphatc fertilizer as a mineral feed suppleof the compound represented by the formula Ca,(P04)1”( 6 ) . ment for animals. Such suitability involves (a) the physiological I n the fourth report of the Combittee on Animal Xutrition of availability of the phosphorus and (b) the toxicity of the comthe National Research Council, Mitchell (8) recommended that ponent fluorine. COMPOSITION OF DIETS the admissible levels of fluorine in a mineral mixture for cattle should be considered tentatively as 0.13%, and in the total dry For the study of effects of fused tricalcium phosphate durinq feed as 0.00370 (30 parts per million). He considered 0.01% the growing period, rats were given four diets that differed fluorine (100 p.p.m.), dry basis, t o be approximately the borderchiefly in the nature of the carriers of phosphorus and fluorine. line content for phosphates fed t o swine, sheep, and cattle. This The diets were designed t o be otherwise identical and adequate recommendation was made on the basis of experimental work in all respccts for normal growth and development, except that done chiefly with ram rock phosphate which contains about 3.SYO phosphorus and calcium were brought t o levels near the minimum fluorine. The committee states that these levels are tentative for rapidly growing animals. At this minimal level any lack of and that additional studies are needed. availability of the phosphorus in the test product is evident. Phillips, Hart, and Bohstedt (11) reported typical fluorine Phosphorus contents ranged from 0.204.24% and calcium contoxicosis in dairy cows when ran- rock phosphate n-as fed as tents from 0.30-0.3570, giving C a / P ratios from 1.4 to 1.7. The 0.62570 of the grain mixture. Phillips et al. (10) state that no diets were modifications of control diet 1, which consisted of injurious effects appeared for the first three years of the experithe following parts per hundred: lactalbumin 18, starch plus ment in which rock phosphate was fed as 0.6257, of the grain yeast extract 68, Snowdrift vegetable fat 8, Osborne and Mendel mixture, but that during the next two years there mas loss in (9) salt mixture 4,and cod liver oil 2. Diet 2 was the same as the weight, appetite, and milk production. control except that phosphorus and calcium were omitted from Tolle and Maynard (1.3)founc! that a phosphatic limestone conthe salt mixture; the fused tricalcium phosphate was the chief taining 0.927, fluorine was utilized as effectively as bone meal source of these elements and constituted about 1% of the total in bone formation. They also found t,hat a group of animals diet. The fused tricalcium phosphate products used contained
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
652
T LBLE I.
CALCT-I.ATE1)
FLUORIKE C O N T E N T OF DIETS F Content, P.P.11. 11 13
Diet Osborne a n d Slendel sal1 iiiixt Dicalciuin phosphate Fused phosphate 0.O4Cc F Fused phosphate, 0.2% F Fused phosphate: 0.3% F Fused phosphate, 0.55% F
15 32 43
67
0.04, 0.2, 0.3, or 0.55(,';fluoi,ilir, and a11 we~'e80-mesh screeninyr. In diet 3, where dicalcium phosphate n-as the chief source of
Vol. 38, No. 6
narily about 15%bone meal is atldrd to the grain mixture; this would be about @.8Yoof the total dry feed, assuming that the grain mixture constitutes 75y0 of the ration. Previous experiments showed that the phosphorus in the control diet supplied by the Oshorne and itlendel salt mixture was in a farm readily available for normal growth and development. The group of rats fed this diet, therefore, served as a criterion by which to compare availability of the phosphorus supplied as fused tricalcium phosphate and as dicalcium phosphate. The diet with dicalcium phosphate was included so that the fused tertiary phosphate could be compared with the binary phosphate that had proved effective in the feeding of farm nnimals.
phosphorus, the salt mixture as modified so that its phosphorw and calcium contents were approximately the same as thost, of EXPERIMENTAL A 3 I3fALS the other diets. Diet 4 x a s the same as the control except that In the gromth experiments, five rats of thc sufficient sodium fluoride was added t o make the fluorine contrnt weight., and of identical nutritional and hereditary hi-tory, w r e identical with the percentages of fluorine furnished by the triplaced on each of the four comparable diets. l'hr :\nimnlr witre calcium phosphate in the variations of diet 2. started on experiment a t 30 to 31 days of age. Fccdirig n-as conDiets 1 and 2 were compared in the breeding rxpcrimt.iits. tinued for 30 days, the period of most rapid growh, but r m b exTwo variants of fused tricalcium phosphate were used in diet tended to 60 and 90 days in which case additional series of five '2 to determine whether products carrying 0.2 and 0.37, fluorine rats each were fed 0.2 and 0.37,fluorine phosphates. .1 quadcan be fed to an animal throughout life, and to succeeding generaruplicate feeding technique was used for equalization of food (#ontions, without vitiation of normal reproduction. To distinguish rumption to minimize the variable due t o individual diff erences between the effects of fluorine toxicity and phosphorus defiin appetite. Body weights were recorded and the carrases ciency, the comparisons were made a t trvo phosphorus levels. At analyzed for phosphorus. one level the phosphorus content was made 0.2% of the total Three breeding experiments were set up a t the following levels diet, approximately the minimum for normal growth to maturity uf phosphorus and fluorine: ( a ) 0.270 fluorine phosphate and if the phosphorus supplied is readily available; the second level controls a t the 0.2yophosphorus level, ( b ) 0.2%fluorine phosphate of 0.4Y0 of the total diet was intended to assure a supply of and controls a t the 0.4% phosphorus level, and (c) 0.3% fluorine phosphorus adequate for growth, reproduction, and lactation. phosphate and controls a t the @.4y0phosphorus level. At (tach The fluorine content of every diet was calculated from thr given phosphorus and fluorine level (for example, 0.27, P and amounts present in the salt mixture and in the mineral supple0.27, F), four parent breeding lots were started, each lot consistments, as shown in Table I. Fluorine analyses of four of the ing of trvo males and three females. Two lots \yere fed the control total diets were made by G. A. Shuey of this stat>ion,with the diet and two received the phosphate diet, the rats on each control following results: 15 p.p.m. for the control diet containing Osdiet being matched with respect to litter and w i g h t with those borne and Mendel salt mixture, 13 p.p.m. for that containing of the corresponding phosphate diet. From the young of each of dicalcium phosphate, 37 p.p.m. for that containing fused trithc four parent lots, two breeding lots were made up; and from calcium phosphate of 0.3y0fluorine content, and 43 p.p.m. for t h e young of each of these second generation lots, onc brreding the one designed t o contain a like amount of fluorine in the form lot w w set up. The young of the third generation (that is, fourth qjf sodium fluoride. The analytical and the calculated value? Ki>nc,wtionrats) were weighed and killcd a t wclnning. In the indicate that fluorine of the diets was derived ~olt,lyfrom th(. I Y I ~ I , of all hrceding lot:', the frmalw wt\w matcd rt~p(':itcdlyover salt mixture and mineral supplements. The level of the fused tricdcium phosphate for the experimental diets Kas chosen so that the mineral supplement vould supply the phosphorus necessary t o bring the total P stored, grams F ill D ~ (~: r o a i~h , grains ~ up to approximately 0.2%. phosrion of Fuarcl Pinil,Fused Probpliarr. erpt., Conphos:ihildigiiificauce Con-' phosahilSignifiaurioe which is the minimal level for days trol phate IIV of difference trol phate ity of difference normal growth and bone de0.04 30 103 103 N o difference 0.479 0 421 0.1 N o t significant velopment during the rapid 0.2 30 100 97 0.5 N o t significant 0.470 0.366 0.01 Significant 0 . 2 60 156 1.50 0 . 5 S o t significant 0.780 0 . 6 8 3 > 0 . 0 5 Not significant growth of Tvhite rats. This 0.2 90 196 197 0.3 S o t significaiir 1.059 1.042 0.5 N o t significant 95 0.01 Significant 0 488 0.382 0.01 Significant 0.3 30 I10 meant that about two thirds 0.3 60 I54 I52 0.5 Xotsignificant 0 916 0.814 0.01 Significant of the total phosphorus war 0.3 !40 185 181 0.5 S o t significant 1.184 1.143 0.1 Not significant 0 s.5 30 112 98 0 01 Significant 0 4R-J 0.332 0 . 0 1 Significant supplied by the fused tricalcium phosphate, the remaindcr being present in the lactalbumin and yeast extract of thr basal diet. Since all of the ___. ~- . ~ . Iiidications from Clroa-tli~---- - - - ~---Indications from Phosphorus Srurage 1' stored, granis _ i : r o~ r t h., _ gram5 ___ .p h o s p h a t e s used contained F 111 DuraDicalUicalabout 137, phosphorus, it wai Fubed cium I'roljphostion of Fused rium I'rub phosphosaSildivii~ficaricc phosphosahildigiiificaiicr phate, expi., necessary to have them constie, days phate uhate it)' uf difference phate p h a t e it\< ) f difference . . tute about 1% of the diet in 0.3 N o t significant 0.01 30 103 I05 0.2 S o t significant 0 121 0.433 S o t significant 90 0.1 S o t significant 0.366 0.407 5.0.03 order t o furnish the desired 30 97 0 2 0.5 S o t rig-nificent 0 683 0.695 60 150 145 0.5 X o t significant 0.2 0.5 Not significant total of that element. In1.042 1.057 90 197 197 X o difference 0.2 0 . 1 N o t significant 0 382 0 . 4 1 1 0 3 30 92 98 0 ,1 S o t signifiraiit cidentally, this is in accordancc 0.5 No%sigiiifioant 0 814 0.831 60 132 143 0.03 Significarit 0 01 Significant 0 3 90 181 180 0 3 S o t signific:int 1 . 1 4 3 I i n n with the amount of bone meal 0 3 Coiituined 0.04': fluuriue. usually recommended in the fwdiny of farm animals. Ordi-
.
-
~
~
1
INDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1946
653
Dicaicium phosphnte of low fluorine content is admittedly :i safe and effective mineral 5upplement for animal feeding, -Indications froni Phosphorus S t o r a q F, DuraP stored, grama prnband therefore was used as a uqu,,-. of Growth. :eftO. expi., Con- Control ahilSignificance ConControl abilRignificaiicr standard of comparison for the da3-s Tro1 t- F It? of difierenre trol +F it? of differenrr Cusec1 products of different J ? 30 100 'Ji O..i S o t significant 0.470 0.447 0. 1 S o t significant 1.2 60 15t'~ 1.53 0 j S o t significant 0.780 0.803 0.5 S o t significant fluorine content. The results 3 2 90 196 2000 0 5 Notsignificant 1.059 1,109 0.1 S o t significant (Table 111) indicate that the 3.3 30 110 1O(r 0.5 Xot significant 0.488 0.492 0 3 S o t signifirant 0.3 60 154 15; 0 5 N o t eignificant 0.916 0.928 0 .5 Xut sigriifirarit specimens of fused tricalcium 90 185 182 0 3 S o t significant I . 184 1.186 0 ,i S o t significant ! : : j 30 112 106 0 .5 S o t significant 0.464 0 467 0 5 S o t significant phosphate tested were as effeerive as the dicalcium phosphate 1 Equivalent t o t h a t in the corrr,pondiiie phosphnta. , i f 0.04Fc fluorine c o n t e n t . Xforeover, any significant difPHVSPHORT'S O F 'THE DIET O S T . 4 H I . 6 \ ' , F;FFFCT OF TOTAL fererices in the experimental I< EPROI~l'~'1'lCJT results \yere in favoi ut tuscd tricalrium phosphate. Fused Tricalciuni DISTINCTION BETWEEN FLUORIXE EFFECTAND INADEQCACY Coutrol Phosphate OF P H n s P H o R c s . The data of Table Iv indicate that sodium so. No. so. No. raised horn raisecl fluoride exerted no adverse effect upon growth or upon phos. ' i i r ~ r r o l 8 8 . 0.2Ig F fusea T r i c n l r i i i r i phorus storage when it was fed in amounts corresponding t o those phosphate Minimal P, 0.2% in diet 391 473 450 N O introduced through fused tricalcium phosphate with a fluorine .idequatP P.0.4% in diet Si8 691 761 445 Increase 87 218 311 1% content as great as 0.55yc. Hence, the differences noted in c in 46 fig 63 /' i n c r e a s e Table I1 may have been caused by a part of the phosphorus of ' h n t r o l 78. 0.3:; F fusea trii'alr~iiii~ the fused tricalcium phosphate being present in a form not, readily phosphate 230 205 :334 616 Slinimal P, 0.2$70 in diet assimilable, rather than by a toxic effect of fluorine.
1' x R 1 . E I\., r
PHYSIOLO(;lc.4L
.%VAILAHILITT O F THE PHOSPHORUS FEDIS T H E CO'JTROI. ALONEASD WITH ADDEDFLTORISE
.
DIET
~
t d e q u a t e P. 0.4% in diet Increase increase
549 133 32
308 103 50
592 258
77
414 184 80
i p,i-iod I J one ~ gear and three months (unless death by accident .ntervencd) ; this is nearly the entire reproductive period in the ivhite rat. A11 young were given sfrial numbers and iveighed a t oirth and a t weaning, a t which time those not used for breeding were killed. Thiq procedure involved sixty breeding lots, with rcpeated matings throughout the reproductive period. I n a digest I f the breeding results, differences cawed by accidental deaths of mothers were eliminated in :in effort t o afford a clear and fair picture O f those effects which might he :ittributed t o the use oi iuwd tricalcium phosphate. For example, when a female in t h r ,.ontrol group died before the rlnd of the breeding period, her :ength of life was noted and a female in the corrrsponding breed.ng lot rccciving fused phosphate W R C piyen credit only for thf, voung horn during a like period. Student's t-test vas used in st:iti>tic,al rtrialysis of the data to -stoblish the significance of differences in results obtained from .he vai,ious diets. The formula used as that given by Goulden ' 4 ) for paired variates. The term "probability" used in Tables 11,111, and IV represents the frequency v i t h which the difference bc,txeen two mean values may be due to chance alone and not to any real difference resulting from the diets. When the probability is 0.05 or less, the difference between the means may be wnsiderrd significant.
PHY SlOLOGlCA L AYAI LAB1 LITY OF PHOSPHORUS
'L'o compare the physiological availability of the phosplioru:: w1)plied as fused tricnlcium phosphates with that of the Osborne
and hlendel salt mixture, the results were subjected to statistical malysis, Table 11. The data indicate: (a) The phosphorus of -he fused tricnlcium phosphate of 0.04% fluorine content is as d e c t i v e for growth and phosphorus storage as that of the Os'iclrne and Mendel snlt mixture. ( b ) The phosphorus of the materink of higher fluorine content is not quite so effectivt: a,-hat of the Oqborne and liendcl snlt mixture. (c) Over the 60ind 90-day periods th? sloner growth i'ate and concomitant de"rease i n need for phosphorus gradual1~-offset the diffcrences in -.ffectivenes Hence the animals fed the 0,3y0fluorine phosphate iirt over a 90-day period show no significant differences in comx i r i s o n n.ith control animals.
REPRODUCTIOX
EFFECTO F TOTAL DIETARY PHOSPHORUS.Table v compares the numbers of young born from and those raised by animals fed phosphorus a t two levels, designated as minimal and adequate. Obviously, the increase in phosphorus level from 0.2 t o 0.4YGresulted in an increase in numbers born and numbers raised to weaning, whether the animals had been fed the control diet or one that contained fused tricalcium phosphate of either 0.2 or 0.3% fluorine content. The mean increase in numbers born for the control diets was 21%; for the phosphate diets, 737,. The meau increases in numbers of rats raised Twre 489, for the control diets and 677, for the phosphate diets. This demonstrates that a n adequate level of total phosphorus is necessary before poor reproductive performance can be ascribed to fluorine toxicity. EFFECT O F FT-SED TRICALCILAI I'HOSPHATE. The data of 'Table VI set forth the reproductiw performances induced by the t n o samples of fused tricalcium phosphate of different fluorine content and by the Osborne and Mendel salt mixture. Since the animals represented by the results in part A bad been on experiment longer than those in parts B and C, the comparison between the groups is made on the basis of percentages rather than total numbers. At the phosphorus level deemed the minimum for growth, the mimals on the 0.2% fluorine phosphate diet produced 67% as
TABLE5-1. FVSEDTRICALCIZTM PHOSPHATE COMPARED WITB ( h H O R S E . 4 S D SIEZiDEL SALT h l I X T U R E A S A Sol-RCE O F P H O R P H O R T 3 FOR REPRODUCTION .t
Sa.Born
.
l l i i i i m n l phosphorus Control (0.& 11. s n l t mixture) 0.2ycF fused tricalcium phosphate (Phosphate)
Control
844 568 61%
N o . Raised
490 391
8870 641 479 75:::
C.
Adequate phosphoruh
Control (0. & 11. salt m i x t u r e ) 0.353 F fused tricalcium phosphate (Phosphate) Control
100
ti23 488
isL.;
.3ii .'3 5 0 93';
654
INDUSTRIAL AND ENGINEERING CHEMISTRY
many young and raised 80yGas many as those on the control diet. This performance tends t o support the growth data in that the phosphorus of the tricalcium phosphate was less available than that in the Osborne and hlendel salt mixture. At the higher phosphorus level the animals on the 0.2% fluorine phosphate produced 85% as many young as those on the control diet and raised 75% as many. The 85% value vould give this phosphate material a rating of "very good" i n relation to the Osborne arid hlendel salt mixture when appraised according t o the method of Ellis et a!. @), who rated as very good a phosphate that was SOc/, as effective as bone meal, n-hen gron-th and bone ash were the criteria. At the adequate phosphorus level, the animals on the 0 3Yc fluorine phosphatc dict produced 78% as many young a s those on the control diet and raised 93% as many. .lppnwntly 7,fluoIirie when reproduction is the basis of comparison, the 0 3 fused phosphate is a satisfactory source of phosphoruq t o rats. SUaIhIARY Ah-D CONCLUSIONS
1. Eighty-mesh fused tricalcium phosphate, containing 0.2 to 0.55% fluorine, was fed at a minimal dietary phosphorus level to white rats during the 30-day period of their most rapid growth. This was found to be less assimilable than inorganic phosphate of the standard Osborne and hlendel salt misture. The difference in degree of assimilability was not manifest when the is, phosphorus demand of the growing animal was less-that during the 60- and 90-day periods. The difference was less apparent also mhen the level of total phosphorus rvas raised from 0.2 to 0.47, in the breeding experiments. With such increases in phosphorus content, there were increases of 53 to SOYc in numbers born and raised on the phosphate diets. 2. When sodium fluoride was introduced into the diet to provide a fluorine content equal to that fed as fused tricalcium phosphate, there was no detrimental effect upon gron-th of the rats t o maturity or upon their bodily retention of phosphorus. 3. The 80-mesh fused tricalcium phosphate containing as much as 0.3% fluorine proved as efficacious as the precipitat'ed dicalcium phosphate in the promotion of rat growth to maturity and in phosphorus storage. 4. Eighty-mesh fused tricalcium phosphate of 0.2 or 0.3% fluorine content was fcd at a 1% level, and the phosphorus con-
Vol. 38, No. 6
tent of the dict n a s brought to 0.4yo. The fused material proved t o be 78-857, as effective as the phosphate of an Osborne and Mendel salt mixture when effectiveness was measured by reproduction, and 75-93y0 when effectiveness Tvas measured by lactation. 5. The data obtained indicate that fused tricalcium phosphate of 80-mesh, containing not more than 0.370 fluorine was virtually as effective as the control phosphate of the Oshorne and Mendel salt mixture, when evaluated by rat growth and body storngc of phosphorus during a 90-day period. When judged by reproduction and lactation, the fused phosphate proved from 75 t o 93T0 as good as the salt mixture. The results also indicate that nutritional ineffectiveness of a phosphatic product should not be attributed to its fluorine content until the factor of low phosphate availability has been taken into account. LITERATURE CITED
(1) Bnrrentine. B. F., Maynard, L. A., and Loosli, J. K., J . Sufrilion, 27, 3 5 4 2 (1944).
( 2 ) Ellis, N. R., Cabell, C. A, Elrnslie, 'A7. P., Fraps, G. S.,Phillips, P. H., arid Williams, D. E., J . Assoc. Oflcinl Agr. Chem., 28,
12932 (1945). (3) Fraser. 13. F., Hoppe, T. C., Sullivan, J. H., and Smith, E. R., ISD.E K G . C H E M . , 35, 1087-90 (1943). (4) Goulden, C. H., "SIethods of Statistical Analysis", pp 42, 2 e i , New York, John Wiley &Sons, 1939. (5) Jacob, K. D., Feedstuffs, 16, 1s-32 (1940. (6) J . r i s s n c . Oficial Agr. Chem., 28,38 (1915). (7) hladntire, 11'. H., Winterberg, S. H.. Hatcher, B. W., a n d Palmer, George, Soil Sei., 57, 42542 (1944). ( S ) XIitchell, H. H., Natl. Resoarch Council, Reprint Circ. Series 113 (1942). (9) Oshorne, T. B., and Mendel, L. B., J . B i d . Chem., 37, 557-601 (1919). (10) Phillips. P.I I . , Bohsteclt, G., Faryo, J. h l . . Hart, E. B., and Haloin. J. G.. Wis. Aar. ExDt. Sta.. Bull. 428.9-12 11934). (11) Phillips, P. H., Hart, E. B.,'and Bohstedt, G., Ibid., Research Bull. 123 (1934). (12) Tolle, Chester, and Maynard, L. A , , Cornel1 Univ. Agr. Expt. Sta., Bull. 530 (1931). PRESEXTED on t h e program of the Division of Agricultural and Food Chemistry of the 1943 Meeting-in-Print, AhrERIcax CHEVICAL 8OCIETY. This study was conducted in cooperation with t h e Tennessee Valley Authority.
VITAMIN CONTENT OF' PEAS Effect of Freezing, Canning, and Dehydration C. H. IIIAHONEY, E. P. WALLS, H. A. HUXTER,ANDL.E. SCOTT M a r y l a n d Agricultural Experiment S t a t i o n , College P a r k , M d .
T
IIE objective of this investigation was to determine, a t the time of serving, some of the nutritive levels of peas. Direct comparisons n-ere made on identical lots a t the same stage of maturity, preserved by canning, freezing, and dehydrni ion. Eight varieties of sweet peas R-ere gro\vn a t the LIaryland station during 1944. The plots rrere large enough so that they could be harvested with commercial equipment and threshed in a standard viner. The shelled peas n-ere thoroughly mixed a t the viner and then separated into the various sieve sizes. I n all cases the prevailing sieve size typical for the variety was used for processing and for vitamin determinations. , The peas were thoroughly m-ashed, cooled, and processed rrithin 2 hours. The variety Dark Podded Thomas Laxton was used i n comparative studies of the three methods of preservation. Large samples of No. 4 sieve peas of this variety mere taken from the same lot for freezing, canning, and dehydrating.
I3laiicliing htudies conducted several years ago at this station indicated that a better quality of frozen peas was obtained by blanching a t 190 O F. than in boiling v-ater, and this temperature was selected for the 1944 studies. Twenty-five to thirty pounds of peas were blanched in a R ire basket in 30 gallons of water in a steam-jacketed kettle where the temperature could be accurately controlled. The peas were agitated during blanching and were then cooled immediately in cold running water. Some lots of peas were blanched with steam. A special steam blanching box with a water seal made it possible to obtain a temperature of 214" F. in the center of 30 pounds of peas in a n ire basket n ithin 30 seconds. All steam blanching treatments were made at 214' F. Samples for freezing viere separated into floaters and sinkers in a 13y0brine after blanching in water at 190" F. for various times. The peas were washed and packed in one-pound, mois-
