INDUSTRIAL AND ENGINEERING CHEMISTRY
Demlllber, 1949
1183
ULTRAVIOLET ABSORPTION
Figure 3 presents plots of the ultraviolet absorption curves for alkali-isomerized methyl linoleate and the fatty acids extracted from soybean flours. Since it had been observed that, during the high-temperature deterioration of soybean flour, an oily distillate collected in the air outlet tubes, highly purified methyl linoleate was added to a solvent-extracted flour to the extent of 10% by weight. Within 6 hours a t 110' C., an appreciable quantity of oily distillate appeared in the air outlet tube of the methyl linoleate flour mixtures. A sample of this decomposition product which was alkali-isomerized had a spectral curve (Figure 3).
TABLEIV. RELATIVESTABILFFIES OF SOLVENT-EXTRACTED SOYBEAN FLOURS AT 100" C. Sample
Manufacturer C
No. 1 2 3 4 5
Stability a t 100' C., Hr. 216 250 232 378 310
%
0.7 0.6 1.3 1.3 0.7
D E
TABLE V. CHANGES IN THE FATTY ACIDSOF FULL-FAT SOYBEAN FLOURS Flour Sample 3B (110' C., 45hour induction period)
I 2
F a t Content,
2B (100' C., 77hour induotion period) 1A (100' C. 46hour induction period)
Hours Aerated
0
36 37 89 43.5 0 72 76
78 79 0 44.6 46.5 49
Peroxide Value
..8
9 15 25 59 39 140 168
..68
249 314
Iodine Value 139 136 133 131 130 138 183 123 102 94 141 135 91 56
Linoleic Acid,
%
Linolenic Acid,
66.6 65.9 64.8 51.5 62.6 67.1 66.1 45.8) 88.6 36.3 55.4 49.36 27.6 7.4
70
8.4 7.7 7.9 7.6 7.7 8.4 7.5 6.9 7.3 5.6 9.2 8.8 9.0 8.6
Iodine
Valueo
...
136 134 128 130
...
134 112 101 91
I29 90 52
Calculated from chan e in diene and triene acid contents. b Value for diene probaby too low.
ACKNOWLEDGMENT
The authors wish to express appreciation to C. B. Shaffer for photographing the apparatus (Figure 1) and also to H. E. Longenecker for continued interest and advice during the investigation. Thanks are also due the 8oy Flour Association for supplying many of the soybean flours for the investigation.
O t
LITERATURE CITED
2 (1) Baldwin, A. R., and Longeneoker, H. E., Oil & Soup, 22, 151 230 250 270 290 WAVELENGTH n Figure 3.
p
Spectral Absorption Curves
1. Oily dbtillate from methyl linoleate deoompomitlon. Math Ilinoleate. 8, 4, 5. 5atty midm from oil extraoted from moybean flour 2Bi 3. no aeration, 4, aerated 78 hours; 5, aerated 79 h o w .
a.
The marked general absorption of this isomerized distillate
ia the region 270 to 280 mp is probably due to carbonyl resonance. Hoiman et al. (6)recently investigated oxidation products of unsaturated fatty acids in this region of the ultraviolet. Their experiments indicated that carbonyl resonance served to increase the general absorption in this region. The inflectionsa t 270 and 280 mp in the three abaorption curves (Figure 3) for the alkali-isomerized fatty acids extracted from soybean flour are indicative of triene acid. Apparently, oxidation reduced the amount of triene acid without the appreciable formation of decomposition products having marked general absorption in this region. The small amount of spectroscopically active triene material in the methyl linoleate represented about 0.5% triene acid. Since the investigation on the soybean flours was aoncerned primarily with rancidification under conditions of accelerated oxidation, the reversion effect of the soybean oil in the soybean flour was not considered since it was difficult to detect. Evaluation of reversion in soybean flour requires the use of a suitable tasting panel. Studies are currently in progress on possible correlation of the stabilities of soybean flours as determined by accelerated oxidation with stabilities determined under varying conditions of controlled humidity and temperature.
(1946). (2) Cha m a ,R. A., and McFarlane, W.D., Can. J. Rmsoroh, B21, l& 11843). - ~ , (3)F i e r y L. J., Jr., Mattil, R. F., and Longenecker, H.E., Oil & Soap, 22, 190 (1946). (4) Frankel, J., and Brown, J. B., J. Am. C h m . SOC.,65,416 (1943). (6) Holman, R. T., etal., Ibid., 67, 1285,1386, 1390 (1946). (0) James, F. E., F a d Indwtriss, 17,492 (1946). (7) Kine, A. E.,Roschen, H.L.,and Irwin, W.H., Oil & Soap, 10, 105 (1933). (8) Mehlenbacher, V. C., Ibid., 19, 137 (1942). (9) . . Mitchell, J. H., Jr., Kraybill. H. R.. and Zscheile. F. D., IND. ENO.CHBIM., ANAL.ED., 15, 1 (1943).
.
(10) Payne, D. 8., and Stusrt, L,B., "Advances in Protein Chemistry", Vol. I, p. 187, New York, Academic Press, 1944.
T R ~work : described wa8 carried out under a contract, recommended by t h e Committee on Medical Research, between the Office of Scienti5c Research and Development and the University of Pitbbwgh. Contribution 550 from the Department of Chemiatry, University of Pittsburgh.
Inhibitors of Corrosion of Aluminum-Correction An error should be pointed out in this article Khich appeared in the August, 1945,issue O f INDUSTRIAL AND ENQINEERINQ &EMISTRY. Two values are given for magnesium in the synthetic tap water analysis near the bottom of the second column of page 738. The second entry a t the end of the table (1.4p.p.m.) should refer to manganese. G. G. ELDREDGE AND R. B. MEARS ALUMINUMRESBIARCE LABORATORIES N l W KElWlNOTOK, P A .
