,INDUSTRIAL A N D ENGINEERING CHEMISTRY
September 1947
(' ~ ~ ' O T E S S COXTENTOF
DEHPUR~TED
ALF~LFA
NEALFROU FIELD So. 2
Origin of Ikhydrared 11eal (
Carotene i n Fresh Sample, IIg./lOO G .
Dry Matter, C'
Carotene, D r y Basis, 3Ig./lOO G .
\itamin
A8
I.t-./I.h
'Iiopped alfalfa directly f r o m field
Chopped alialfa after 2 . 5 h r . on truck C'h c pped a l f alia a f t e r 4 . 5 h r on
dwk
LO>. U! Carotene during Dehydration, C,?
1165
nidi to thank \V. J. Small for the intcli,twt anti close cooperation which made this Ytutly possible. The authorl: are also indebted to \Villiani 13. Honstead and \V. G. Ychrt,itk for assistanci: in sccuring and prtJparing saiiiplos for :iiialysis, and to IT. Ci. Schrcnk ior the spectrophotomt~lric readings. This work was supported by The Kansas Industrial Development Commission.
LWER41'UR E f :ITEL> ( I ) Cary, 1 4 . H . , aiid Becknmii. :\ O . , . / . Optical Soe. Am., 31, 682 (1941) ( 2 ) ('harke>-,L. W., arid JTilgus. H . S..$11 ., I s o . K s o . ( ' H E M . , 36, 184 (1944). ( 3 ) Moore, L. .A,, and Ely, I{., IN^. I:v(,, ( ' H E M . , As.ii.. ED., 13,600 (1941). (4) Silker. R. E.. Schrenk. W.G . and ~ Kiiin. fi. H . ,
Vapor Pressure of Water Adsorbed on Dehvdrated Alfalfa T h e Fapor pressure of water adsorbed on dehbdrdted alfalfa w a s measured iu the region of 2.2 to 14.17' moicture and in the teniperature range from 17 O to 50" C. \&orption isotherms are the tSpical S-qhaped isotherm- of other similar materials. Isosterio plots of the data were rnatle h> the method of Othnier and Sawjer (6), and the ratio. het w e e n the heat of adsorption ofwater h) alfalfa meal t o the heat of taporizatioii of water at the .anie teniperature were calc*ulated. This paper Show5 that proteiu cwntent. withill the range itudied, has little effect on the Tapor p r e s u r e . Blanching the alfalfa meal prior to dehjtlratioii does r i o t appear t o d l t e r the position or shape of t h e \'il)or i)re-*urt' i iir\e*.
REC'EXT pxpei' ( 7 ) iridicatcd that a wlatioii inay exist beturc contt'nt and cai'oteiit: rc~tt~iition in dehyiiw thehi: d a t a niay make it desirable to dchy(irate' alfalfa to a known iiioistui.t, content, ini'ormation regarding vapor presswe rquilibrium data ticv>nicv iiecessary, not only for the dehydration pi'oceus, but also for purposes of dctcrmining optiniuni storage c*onclitions aiid iritlicirting type< of packaging
materials ivhich i ~ o u l dtic drsirahle. This paper therefore prwents data regardiiip th(8 i ~ i p i ~ prt'.-r sur(. of watcr adsorbed on dehydrated alfalfa and iiiclicat i+ i1.G u d u l n e s s to t h e industry. Two different commercially dehydrated alfalfa 1 1 i c 4 r aiid one' ateam-blanched sample produced in this laboratoi,~were investigated; they contained 20.1, 15.2, and 19.3Ycprotein, respectively. The blanched sample \vas prepared by placing fresh alfalfa in a steam cabinet through which live steam was passed a t atmospheric pwssure foi, 10 miriutes before the alfalfa was dehydrated.
Iloistures w~xrcadjustcti in the laboratory by iiit'aiis oi' a vacuuin ovcn lor thr ]OR. values (operated a t room tcinperaturt~)aiid a reiiiprratnrc:-ti~iniidity cabinet for the higher levels. XIoisturi. 1 1 ~ ~ :tpprosimating ~~1s 2, 3, 5 , 7 , 10, ailti 14?;, idculatrti on a dry \vcight basis, were obtained. Thc moisture contents of the samples were tleterniiiit~dby placiiig the samples in a vacuum o w n a t 100" C. f o r 2 hours. I'rcvi011s nieasui'enieiits had iiidicatcd no further loss of \wight in this type‘ of material after 2 hours. Vapor pressure nieasurt!rnr~nts art' ia\pi,cssed in terms of these determiiiations. The equilibrium vapor pressures wercy deteriiiincd by the ~uanoiiicstric method described by Makoiver (3, 5). For low prcssures (txdow 30 mni. of mercury) dibut,yl pht,haltitr was used i i i the ilianometer; for higher prrssures mewury wa+ used. For this lorvc~rtemperatures the flask containing the ssinplc was placxudin H constant tc:nipvrature water bath, and for higher tcmperat~ure,~ t lie entire unit vas plareil in a constant tc~mperaturr? air cabirier , *I) that the moisture in t h e system woulcl riot condense. Sample5 i i f approsimatcly 10 graiiis w r v usrtl. All coiinectii)ns w(m. made by means of ground glass joints and stopcocks. The techniques iif cvacuation aiid making readings ivi-re also ~iniiliirto those. described by Makower (3,5 ) . During evac-untion thc nioi?ture trap WLS coolcd to -80' C. by nw:iiis of 511 :ic~btone dry ice iiliuture. IIeaaurements were first made a t thr low ternpcraturw and then at successively higher temperature6 up to 50 O C. Pressure r t d i n g s n'w~continued for several hours, although equilibrium was apparently attained in 30 t o 45 minutcs. It, was found possible to return to lower temperatures after m:ikirig i i w:uling at a higher temperat,urcs and to repeat the previous reading within t:sperimental wror, This would indicate thin rc bility (JE the sorption priii'tw xithin the limits of the oxp(siiincnt. ~
1166
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 39, No. 9
MI
€u
G 4 J
1
-r % HiC 14.1 I
75,
\ \
5.1
\
10.1,
I
4.2
4 4
3.1,
\ \
\
q
\
\
\ \
k
\ \ \
0
w
cz a
1_I
I
A
SURE OF
WATER, MM. HG
Figure 1. Isosteres of Water .idhorbed on Dehjdratcd Alfalfa Meal at Moisture LeFels between 2.1 and 1 I.1pIc
Xo difficulty with carbon dioxide as meritioncd by Alakoivcr (3I w~ experienced, although the high temperature (70' (',) : i i which he worked was not used. DISCUSSION AND RESULTS
The vapor pressure data obtained are given in Tablc I. Tlit~w data w r e obtained by plotting measured w p o r pressure against moisture content. Graphical interpolation then pei,inittcd t 111, construction of the table. If the data are treat,ed by the met,hod d w c r i b d !>yOtliincir iinii Sawyer (5),they may be interpreted graphically as shown i r t Figure 1 by plotting the vapor pressure of water in equilibti.in~ with the dchydrated alfalfa against the vapor pressure of 1rui'c' water at the same temperature. This gives a linear plot which permits extrapolation, within reasonable limits, to lower or Iiigtir~r tymperaturrs. The experimental data fit straight, lines uiccl>.. As has been shown for white potatoes ( d ) , blanching produew n c,hange in the dehydrated product which is reflected in chanyc.. iii the vapor pressure data; consequently it was thought advis:rl)lta t o obtain vapor pressure data on steam-blanched alfalfa mc:tl. When t,his procedure was follon'ed, the type of change in vapiir pressure, due to blanching white potatoes, was not observed. anti the data obtained were identical with those obtained oti u t i blanched samples. Hoivcv~r,commercial dehydration of alfalfa is a rapid process; it occurs a t high temperatures and thcr(~foi~i~ differs considerably from the usual vegetable dehydration procedures. This may account for similarit it:< obtained undct. t Figure 2. two conditions, since it is possiblr that alfalfa is alniost wltI i ( b
idsorption Isotherms for Deh?drated ilfalfa \leal at 30' and 30' C.
September 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
low humidities and the beginning of multilayer and capillary adsorption. The isotherms of Figurr 2 suggest that the'adsorption data should follow the theory of Brunauer, Emmett, and Teller ( 1 ) . Calculations based on their equation were made but are not presented here, because more rsperimental points would be desirable for proper handling of these data. However, it was noted that, ) approximately in the region of relativo pressure ( P , ' P o betncxen 0 . 2 and 0.5, the data approsimatecl a straight line in accordance with their thc~ory. 4CIiNOW LEDGMENT
The' :assistance. of Dale Eoivlin in making sonw of thc vapor piwmeawi'enients is gratefully acknowledged. This work was supported hy the Kansas Industrial Developmc~ntCoininision.
1162
LITERATURE CITED (1) Brunauer, S..Enimett, P. H., and Teller, E., J. Am. C'hem. Soc., 60, 309 (1938). (2) Emmett, P. H., "Advances in Colloid Science," p . 1 , New Tork. Interscience Publishers, I n c . , 1942. (3) Makower, B., IXD.ESG.CHEY.,37, 1018 (1945). (4) Makower, B., and Dehority, B. L., Ibid., 35, 193 (1948). ( 5 ) Makower, B., and Myers, S . , Proe. I n s t . Food Tech., 4th C o n f . . 1943, p. 156. (6) Othmer, D., and S a w e r , F. G . . IKD. E s u . CHEY.,35, 1269 (1943). (71 Silker, R. E., Schrenk, W.G.. and King, H. H., I b i d . , 39, 1160 (1947). (8) Stamin, .-i. J., and Millett, AI. A , , J . P h y s . C'heni., 45, 43 (1941). (9) Wilson, R. E., and Fuwa. T., IXD. ESG. (:HEM., 14, 913 (1922).
SUI'('
Contribution 320 f r o m t h e Department of C h e ~ i i ~ ~ tl irnyn ., i i r Y t a t e C'ollege.
Industrial Aspects of Browning RGaction H. Ar. BARNES AND C.
w.
K.IUFMAN
Geriercrl Foods Corporntiori. Hobolien,
T h e browning reaction in foodstuffs ib attributed to a reaction between reducing sugars and proteins or other amino bodies. This reaction has steadily achiered increased recognition as a factor in the forniation of color and flaror in foodstuffs since 3Iaillard published his paper on the reaction of amino acids with glucose in 1912. The flavor and color effect of the browning reaction niaj be either desirable, as in the drying of malt and i n bahing. or undesirable, as in the storage of dried fruits and iepetables. The experience in the General Foods laboratories with dcsiccated coconut and tomato is summarized. The stud, of the formation of flaiors from the reaction of pure amino acids with reducing sugars rebulted in the discorery that aminobutSric acid and others of similar molecular weight giie rise to a flaior similar to that of maple.
M
AILLARD presented his paper in 1912 on the action of amirio acids on sugars to produce what, he called inelanoidins, dark colored nitrogen compounds of high carbon content (24). Lafar (19) followed t,his 4.ith his study on foam fermentation in the sugar industry, and Ruckdeschel (29) with a consideration of this reaction in kiln malt, lvhereupon t h P ;\Iaillard r ~ e tion took on industrial importance for the first tinie. Ppasmodically, during thc early 1920's and in increasing tempo through the 1!)3O's, the information on the Xaillard reaction grew, t o reach a climax during the recent riar years. Today it is the subject of estensive programs in many industrial laboratories and a major effort of a coordinated attack by university, government, industrial, and private laboratories under the sponsorship of the United States Office of the Quartermaster General. Until the war ?-cars the AIaillard reaction had been just slightly more than a laboratory curiosit,y. Then operations in the tropics developed food spoilage problems attributable t o the browning reaction and necessitated immediate study to develop a means of control. =\ctually. the problrm was not ney, but it now became inipoi,tant. Earlier investigators had recognized the reaction in the sugtr industry (9, 19, 53). the beer industry (11. 201, malting (21, 22, 23, 2.91, and milk (28). 1Iore recent work has demonstrated like drt,eriorative effects on dried eggs (3,4,20, SB), molasses ( 7 ) , dehyclrated vegetables (8, 271, dried fruit (1.5, 30.
Y. J .
S I ) , dried juicos (161,bwaliiast cwc,al ( I T ) , wcoriut, (f7),soups (171, ancl dried fish and ineats (17). I t is undoubtedly a factor in the crumb color of h e a d s and cakes and is suspected of being responsible for off colors developed in canned goods during process ing. There is some indication of its occurrence in wines. One glance at this list is, the authors believe, sufficient,justification for the importance no signed to the Ifaillard or browning rwvtion, in so far as the food industry is concerned, and its eventual control assumes great importance in our plans for nwareli today. Thv course of the reaction between amino acids arid sugars has bec.11 .studied by carbon dioxide evolution (1, 2 , 6 , 1 4 ) , color change of reaction products (23), decrease in amino nitrogen during the course of the reaction (2, 6, 18), decrease in pH which occurred a s the free amino groups were used u p (6, I S ) , increase in property of reducing methylene blue (6, 12, 1.41, freezing point determin& tion ( 1 2 ) , and the change in optical rotation ( I $ 14, 26). Euler ( 1 2 ) showed t h a t the decrease in free glucose determined by \~illstatt.er-Schudel method coincides with the decrease in amino acid deternlined according t o Van Slyke, and both are i n agreement with the results of the freezing point determina tioris. The velocity of the reaction depends on t,he nitrogen compound and carbohydrate used, conditions of coiicwitration, temperature, p I l and time of heating, and the presenre of accelerating and inhibiting agents. Nore recently, fluoresccmce has come to the fore as a tool in measuring the coursc of the rcac-' tion, ancl Dutton and Edwards ( I O ) report the colored compounds and the fluorescent compounds as identical. The present work confirmed this to the extent of showing that t,hc color and fluorescrnce curves are parallel, but with an interesting exception. I n tho pi'esence of bisulfite the ratio of fluorescence to color was shout five times that of an unprotected samplc,. BASIC RESEARCH WORK
In our own laboratories n-e have attacked this general problem i n two ways. Our basic rcscarch group has proceeded from the premise that a study of the reactions between individual anlino acids and individual carbohydrat,es would ultimately develop a sufficient understanding of the reactions involved, so as t o e m b l e this type of change to be controlled much more rationally than al;
