INDUSTRIAL AND ENGINEERING CHEMISTRY
586
Liquid and carbon were observed in all experiments. The highest yields in volume per cent of acetylene, ethylene, propene butenes, and butadiene were 76.6, 42.6, 22.6, and 23.3, respectively. The volume of cracked gas reached a maximum in every pyrolysis except that of propene and 1-butene a t 1100" C. and ethylene a t 1400' C. in the range of contact times studied. A change in the reaction mechanism is suggested as a possible explanation. The yields of paraffins were above 25 per cent except in the case of ethylene and propene. Hydrogen is an important product a t the longer contact times in all pyrolyses, the yield increasing with the contact time with but few exceptions which are probably due to experimental error. The relative stability a t l l O O o C. decreases in the order: ethylene, propene, 2-butene, 1-butene, isobutene. The severe conditions of pyrolysis completely masked the primary reaction products because of extensive decomposition. I t is pointed out by experiment and theoretical considerations
+
VOL. 28, NO. 5
that the decomposition of olefins is preceded by polymerization and that the gaseous products are produced by secondary reaction.
Literature Cited Egloff and Parrish, paper presented before Division of Petroleum Chemistry a t the 13th Midwest Regional Meeting of American Chemical Society, Louisville, Ky., Oct. 31 t o Nov. 2, 1935. Egloff, Schaad, and Lowry, J. Phys. Chem., 35, 1825-1903 (1931). Egloff and Wilson, IND. ENG. CHEM.,27, 917 (1935). Hurd, Ibid., 26, 50 (1934); Hurd and Eilers, Ibid., 26, 776 (1934). Hurd and Goldsby, J. Am. Chem. SOC.,56, 1815 (1934). Hurd and Spence, Ibid., 51, 3356 (1929). Lebeau and Damiens, Ann. chim., 8 , 221 (1917). Norris and Reuter, J. Am. Chem. SOC.,49, 2624 (1927). Rice, Trans. Faraday SOC.,30, 152 (1934). Tropsch and Mattox, IND.ENQ.CHEM., Anal. Ed., 6 , 104 (1934). R E C ~ I V EDecember D 26, 1935. Presented before the Division of Organic Chemistry a t the 90th Meeting of the American Chemical Society, San Francisco, Calif., August 19 to 23, 1935.
EFFECT O F HEAT ON
NUTRITIVE VALUE OF
SOY-BEAN OIL MEAL
I
N SPITE of the established place of soy-
bean oil meal in animal feeding, no work has been reported on the effect of variation in the amount of heat used in the manufacturing process on its nutritive properties. Up to the present time, nutrition investigators have paid no particular attention to the history of the samples of soy-bean oil meal studied beyond determining the process by which they are manufactured. The fact that some of the results were a t variance with others indicates that there were differences occurring among the samples used. I n previous studies on soy-bean oil meal by the authors, no particular advantage could be attributed to meals prepared by any of the manufacturing processes in common use, since the commercial meals studied were equally satisfactory in protein efficiency regardless of whether they were prepared by the expeller or by the hydraulic process ( I O ) , and since part or all the meat scrap in a practical chick ration could be replaced by solvent-process soy-bean oil meal with equal or superior growth (11). One sample of hydraulic-process meal, however, was slightly inferior in protein efficiency in these studies ( I O ) . This behavior was attributed tentatively to insufficient cooking, since this meal had a slightly raw, beany flavor and a light color. Probably, therefore, differences in the nutritive value of soy-bean oil meals were due to differences in the amount of heat treatment rather than to characteristics peculiar to the process. That these differences may occur was shown by the work of Osborne and Mendel (6) and of Robison (7') who reported that feeding soy beans cooked a t a high temperature improves the growth of rats and swine, respectively, over that
H. S. WILGUS, JR., L. C. NORRIS, AND 0 . F. HEUSER Cornel1University, Ithaca, N. Y.
obtained with raw beans. This work appears to substantiate the demand in the field for a well-cooked meal of brownish color and without any raw or beany flavor. On the other hand, an excess amount of heat might be harmful as indicated by the reports on the detrimental effect of heat op cereal proteins by Morgan (6) and on fish meal proteins by numerous investigators previously cited by the authors (9). Because of the lack of definite information on the effect of heat treatment and in view of the increasing production of soy-bean oil meal, it appeared highly desirable to determine the effect of the amount of heat used in the manufacturing process on the nutritive value of the meal.
Experimental Methods Since the nutritive value of common protein supplements has been shown to be due to quality of the proteins and to their content of growth-promoting vitamin G, the relative protein efficiency and the relative vitamin G content of the samples of soy beans and soy-bean oil meal were determined by methods described elsewhere in detail (IO). The relative protein efficiency is an expression of the utilization for the growth of White Leghorn chicks of the protein of a protein supplement when combined with an equal quantity of protein from yellow corn meal and wheat flour middlings. It was obtained by determining the percentage of protein stored during the seventh week of age, dividing the percentage storage by that of a standard diet in which casein was used as the protein supplement, and multiplying by 100. In the vitamin G studies, day-old White Leghorn chicks were depleted of their natural reserve of vitamin G by placing
MAY, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY T.4BLE
Sample No.
1 2 3 4
Soy-Bean Material
Beans Oil meal Oil meal Oil meal
OF MANUFACTURING PROCESS UPON RELATIVE PROTEIN EFFICIENCY I. EFFECT
Drier-Temp. Time c. Min.
7 -
.....
100-112 100-112 100-112
..
8
8 8
Beans Oil meal Oil meal Oil meal
9
Beans Oil meal
8
..
66-80 60-80 60-80
60 60 60
-Heater-10 a
Ground several weeks before use.
io
---ConveyerTemp.
Time
c.
Min.
-Prewarmer-Temp. Time c. Min.
Expeller Process
si:90
82-90 82-90
'i 7 7
13 13
100-112
13
ib
66 60 60
i0
Si 105 121
45
them for 2 weeks on a ration deficient in this vitamin but complete in all other respects. They were then fed the basal ration to which 5 or 10 per cent of the material under study was added. The differences in gains during the following 4 weeks between the pens receiving the supplemented rations and a pen receiving the basal ration were compared to those obtained by feeding graded amounts of a standard dried pork liver. The relative vitamin G content was expressed in percentage with dried pork liver as 100, and was obtained by dividing the amount of standard pork liver which afforded a gain equivalent to that obtained on a supplemented ration by the percentage of supplement used and multiplying by 100.
it,
TABLE
Sample NO.
1
2 3 4
75165 75-65 80-68 -Aerator
98
Conti;luous Ground immediately before use.
----Press
90 90 90
10 10 Solvent Process -Extractor---Drier-
7-
105 112-125 130 140 150
..
..
Relatiye Relative Proteln Vitamin G Efficiency Content
Expeller-Temp. Time O c. Min.
.....
..
.....
90
100-112
Hydraulic Process --Heater-Cooker-
-Drier--
5 6 7
587
7i3145
2 '0 1.5 1.0 1.5 1.0
50-60 50-60 50-60
38 a 47 80
2 2 1
84
2
60b
3 2
80 88
3
82
3
57b 92
4 3
and Cooler-
lOi0
OIL MEALS 11. ANALYSISOF SOY-BEAN
Soy-Bean Material
Beans Oil meal Oil meal Oil meal
6 7 8
5
Beans Oil meal Oil meal Oil meal
9 10
Beans Oil meal
Moisture
Protein
Ether Extract
Ash
%
%
%
%
19.56 6.77 5.12 4.87
4.30 4.98 5.24 5.34
18.20 4.84 5.09 4.97
4.06 5.00 5.47 5.56
18.78 0.56
4.78 5.97
Expeller Process 8.94 34.32 7.30 39.84 6.59 43.68 6.39 42.72 Hydraulic Process 36.75 7.18 43.43 10.65 45.76 5.59 6.00 45.58 Solvent Process 6.92 35.73 7.51 46.06
Preparation of Soy-Bean Oil Meals When the cooperation of various manufacturers of soy-bean oil meal was sought, the authors were informed of the study undertaken on the same subject by J. W. Hayward, of the Wisconsin Agricultural Experiment Station. At the sugges-
Soy-bean oil meals which are satisfactory as sources of high-quality protein for feeding poultry may be produced by the expeller, hydraulic, and solvent processes, by the application of a sufficient amount of heat. The optimum temperature found in this study for the expeller method was 140" to 150" C. for 2 minutes in the expeller, and for the hydraulic method was 105" C. for 90 minutes in the cooker. A solventprocess meal produced at 82" C. for 15 minutes (the usual commercial procedure) was excellent in protein efficiency. The vitamin G content of the soy beans studied was low and was not affected to any measurable extent by the manufacturing processes. The color and flavor of the meals were not infallible criteria of their nutritive value, but a raw, beany flavor was indicative of an insufficient application of heat and a resulting inferior protein efficiency.
tion of one of the manufacturers, Hayward kindly supplied the experimental samples used in these studies together with samples of the raw beans from which the meals were prepared. These samples were produced a t commercial plants under his supervision and under controlled conditions by the expeller, hydraulic, and solvent processes. Samples were prepared by the first two processes a t low, medium, and high temperatures. The medium temperatures are generally used commercially. Only one solvent-process sample was prepared, since the temperature could not be varied to any marked extent. The essential data on the preparation of the samples are included in Table I, and the analyses for moisture, protein, ether extract, and ash are given in Table 11. The soy beans used in the preparation of the various samples by each of the three processes consisted of the following varieties or mixtures of varieties: Process Expeller Hydraulic Solvent
Sample No. 1-4 5-8 9-10
Variety Illini Manchu and Illini Illini, Manchu, some Black Ebony
Effects of Processes
KO effect of the amount of heat treatment was apparent on the analysis of the meals. In the expeller-process meals, the protein content of low-temperature sample 2 was slightly reduced, became of a slightly higher moisture and fat content resulting from the low pressure exerted in the expeller. The very low fat content of the solvent-process meal was caused by the nature of the extraction process. The biological results are presented in Table I. No significant differences in relative vitamin G content were found between the raw soy beans and the soy-bean oil meals, since all of the values were within the range of experimental error. The vitamin G content of all the samples was low, averaging
588
INDUSTRIAL AND ENGINEERING CHEMISTRY
about 3 per cent of that found in the standard liver (or about 15 per cent of that present in dried skim milk). This is in agreement with the values previously reported by the authors on other samples of soy-bean oil meal (10). On the other hand, the effect of amount of heat on the relative protein efficiency was very marked, since a difference of 4 was previously shown to be significant (IO). All the raw bean samples were found to be inferior to the meals. The low value of these soy beans is in agreement with unpublished data a t this laboratory and with published results; the most outstanding were those of Tomhave and Mumford (8) with chicks, Osborne and Mendel (6) with rats, and Robison (7) with swine. The low value found for soy-bean sample 1 may have been due to the oxidation of the fat during the time elapsed between grinding and feeding, since it was not fed until several weeks after grinding, whereas samples 5 and 9 were incorporated in the rations immediately after grinding. In some unpublished work, a value of 31 was also found for another sample of soy beans fed a number of weeks after grinding. Both of these samples were unpalatable to the birds. Mitchell and Smuts (4) showed that cystine is a limiting factor in the biological value of soy-bean protein; Csonka and Jones ( 1 ) reported that the chief protein, glycinin, of soy beans is higher in cystine (but not in tryptophan or tyrosine) in the Manchu variety than in the Illini variety. Probably, however, the difference in cystine content was not responsible for the differences in protein efficiency obtained between raw soy-bean sample 1 and samples 5 and 9, since the basal ration used was well supplied with this amino acid by means of the proteins from corn and wheat ( 3 ) . Furthermore, the cystine content of the glycinin from the Illini variety, 0.74 per cent, is more than double that generally accepted for casein, 0.33 per cent (2). There were no consistent differences in protein efficiency between the soy-bean oil meals produced by the several processes; but within processes where controlled temperature variations were applied to the soy beans, significant differences were obtained in protein value. In the expeller method the highest protein efficiency was found for the meal subjected to a temperature of 140" to 160" C. in the expeller. This sample had a pronounced nutty flavor, a slightly roasted odor, and a brown color. Themeal produced a t about 125" C. was slightly inferior in protein efficiency. It possessed a mild nutty flavor, no roasted odor, and a light brown color. The meal produced a t 105" C. with a water-cooled shaft was of little more value than the ground soy beans. This meal had a distinctly raw, beany flavor and a light yellow color. In the hydraulic process a cooking temperature of 105" C. gave the highest protein efficiency. This meal had a cooked flavor and a light brown color. The meal produced a t 121" C. was poorer; this temperature, therefore, is above that a t which the product may be produced without some detrimental effect. This sample possessed a cooked flavor and a brown color. Even the temperature of 82' C. produced a meal of fair protein quality, although it was slightly raw and beany in flavor and light in color. The relative protein efficiency of the solvent-process meal
VOL. 28, NO. 5
was good. Apparently the cooking effect in the two drying periods was sufficient even at the moderate temperatures used. This sample had no distinct flavor or odor and was light in color. These results show that the main factor in the production of a soy-bean oil meal of high nutritive value is the amount of heat applied in the manufacturing process. It is a function of both the temperature and the length of its application. In the expeller process the very short time of exposure to heat was apparently compensated by the higher temperatures used. Probably the pressure within the expeller should be such as to raise the temperature as high as possible without scorching the meal or injuring the quality of the oil (around 140" C.). A good yield of oil is also thus attained. In the hydraulic process the low temperatures used were compensated by the longer time of exposure to heat. The optimum temperature found in these studies was 105" c. In the solvent process a low temperature for an even shorter period of time than in the hydraulic method appeared satisfactory for a reason not yet apparent. Possibly the solvent exerted some beneficial effect. The color and flavor of the meals were generally in direct correlation with the amount of heat used in their production. A comparison of color and flavor with relative protein efficiency shows that the expeller-process meal, which possessed a brown color and a distinctly nutty flavor, was of high nutritive value. This was not true of the hydraulic meals, since the one subjected to the highest temperature was slightly inferior to the one produced a t the next lower temperature. Nor is it true of the solvent process meal which was nearly as light in color as the ground beans and possessed no pronounced flavor, but was nevertheless of excellent protein efficiency. These results therefore demonstrate that the color and flavor of soy-bean oil meal may not offer infallible criteria of its nutritive value. It is probable, however, that a meal of raw, beany flavor is of inferior value because of insufficient heat treatment. Upon comparing the relative protein efficiencies obtained in these studies with those previously reported ( I O ) , it is evident that in this respect properly prepared soy-bean oil meal is generally superior to meat scraps and only slightly inferior to most fish meals. Other unpublished experiments in this laboratory substantiate this evidence.
Acknowledgment Acknowledgment is hereby made of the cooperation of the Grange League Federation Exchange, Inc., of Ithaca, N. Y . , which made this investigation possible by establishing a temporary investigatorship a t Cornel1 University.
Literature Cited (1) Csonka, F.A., and Jones, D. B., J.Agr. Research, 46,51 (1933). (2) Jones, D . E., and Gersdorff, C. E. F., J. Biol. Chem., 104, 99 (1934). (3) Mitchell, H . H.,and Hamilton, T. S., "Biochemistry of Amino Acids," A. C. S. Monograph Series 48, New York, Chemical Catalog Co., 1929. (4) Mitchell, H. H., and Smuts, D. B., J.Biol. Chem., 95,263 (1932). (5) Morgan, A. F., Ibid., 90, 771 (1931). (6) Oshorne, T.B.,and Mendel, L. B., Ibid., 32,369 (1917). (7) Robison. W. L.. Ohio Am. Exat. Sta.. Bull. 452 (i930). ' (8) Tomhave, A. E., and Mumford, C. W., Del. Agr. Expt. Sta., Bull. 183 (1933). (9) Wilgus, H . S,Jr., Norris, L. C., and Heuser, G. F., IND.ENG.CHEM.,27, 419 (1935). (10) Wilgus, H. S., Jr., Norris, L. C., and Heuser, G . F., J . Agr. Research, 51, 383 (1935). (11) Wilgus, H. S.,Jr., Norris, L. C., and Heuser. G. F., unpublished results. 1
,
RECEWEDDecember 2 , 1935.
I
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