I,VDVSTRIAL AND EArGINEERILVGCHEMISTRY
July, 1931
833
The Volatile Products and Water-Soluble Proteins in Cottonseed Meats as Related to Variations in Cooking Conditions' M. K. Thornton, Jr., and C. R. Bailey AGRICULTURAL AND
MECHANICAL COLLEOE O F
HE principal factors which influence the cooking of cottonseed meats are moisture content, temperature, time of heating, rate a t which the temperature is raised, and agitation. The yield and quality of the products are also influenced by the temperature of the press and the speed with which i t reaches the point of maximum pressure. The relative importance of these factors has been a subject of lengthy contention among oil-mill operators. It was hoped that a study of the gases evolved during the cooking and the variation in the water-soluble nitrogen compounds in the cake would aid in understanding the chemistry of the cooking process. The purpose of this investigation was to determine the relative amounts of the volatile acids and bases and water-soluble nitrogen compounds produced during cooking, and the effect of varying the temperature and the rate of heating upon the amount of these substances.
TEXAS, COLLEGE
DIVISIONS OF
COOK
Degrees
COOK
___.
1 1017 1 2 3 4
5 Mean
1 2
3
Mean
1044
110
112R
4
Jfinuies
Minutes
Minutes
Minutes
TEMPERATURE ENDOF Coox O
c.
TEMPERATURES FOR ALL O
c.
O
71.1
101.7 104.4 107.2 110.0 112.8
c.
93.3 93.3 93.3 96.1 96.1
71.1 71.1 76.7 76.7
COOKS
c.
c.
98.9 98.9 98.9 107.2 104.4
101.7 104.4 107.2 110.0 112.8
A steam-jacketed pipe led the gases from the cooker to a straight metal condenser. The discharge end of the condenser was fitted with a rubber stopper so that a flask containing measured quantities of standard acid could be easily attached and removed. The main purpose of this flask mas t o collect the condensate. A tube leading through the stopper conducted the gases from this flask to a U-shaped scrubber, which contained a measured quantity of standard acid and glass beads. From the scrubber the gases passed through
NITROGEN C O M P O U N D S IN
(%
___
Centigrade
1072
SOLUBLE
3
Data for Runs 1 t o 5 Inclusive
Table 11-Analytical
1
-
COOK
2
AT
Received December 23, 1930.
NITROGEN COMPOUXDS IN RAWMEATS( % "3)
TIMEOF
1
1 2 3 4 5 6 7 8 9
The cotton seeds used in these experiments were of good quality and remained in good condition throughout the experiments. They were obtained in two lots from upland fields located near the Agricultural and Mechanical College of Texas. These seeds, having been obtained from the same type of land in the same locality, showed very little variation in composition. The seeds used in cooks 1 to 5 contained 4.13 per cent ammonia (21.25 per cent protein) and 20.8 per cent oil, those used in cooks 6 to 9 contained 4.18 per cent ammonia (21.5 per cent protein) and 19.8 per cent oil. The seeds were cleaned, delinted, and decorticated. The meats, with the necessary hull bran, were then rolled and flaked. The ammonia in the meats used in cooks 1 to 5 varied between 6.03 and 6.25 per cent and that in cooks 6 to 0 between 6.4 and 6.8 per cent. The decorticated meats were passed through a series of cast-iron rolls to reduce them to a thin flake, and then passed to the cooking process. This process consisted of mixing
SOLUBLE
of Conditions of Cooking
Table I-Variations
Experimental Procedure
1
TEXAS
the meats with sufficient water to bring the moisture to 12 per cent and then cooking them in a large steam-jacketed cooker which had revolving sweeps arranged a t the bottom for mechanical agitation. After passing through suitable stages of time and temperature, the cooking process was complete. The cooked meats were wrapped in camel's-hair cloths and pressed into loosely formed cakes. These cakes, while still hot, were transferred t o a warm hydraulic press where the oil was expressed.
T
1
STATION,
'x __-
1044
Degrees
1072
0.1 N XaOH REQUIRED TO NEUTRALIZE CONDENSATE
c4KE
"3)
Centigrade
110
Degrees Centigrade
1128
Mean
101.7
104.4
107.2
110
112.8
7c
%
%
%
%
~
70 %
%
%
%
70
cc.
cc.
cc.
cc.
cc.
0.96 0.96 1, 0% 1.02 0.96 0.96 0.95 0.95 0.94 0.94 0.96
0.96 0.95 1.02 0.95 0.95 0 96 0.94 0.95 0.96 0 96 0.96
0.96 0.96 1.02 0 95 0 95 0 96 0 95 0.95 0 94 0 94 0 96
0.96 0.95 1.02 1.02 0.95 0.95 0.96 0.95 0.94 0.94 0.96
0.96 0.95 1.02 0.95 0.95 0.95 0.95 0.95 0.95 0.95 0.96
0.79 0.72 0.74 0.72 0.53 0.65
0.56 0.65 0.56 0.71 0.75 0.57 0.55 0.62 0.76 0.65 0.64
0.73 0.73 0.68 0.63 0.53 0.85 0.59 0.80 0.78 0.76 0.71
0.61 0.64 0.60 0.58 0.61 0.57 0.61 0.58 0.70 0.54 0.59
0.67 0.65 0.65 0.67 0.67 0.63 0.60 0.66 0.74 0.70 0 66
4.8 4.0 5.8 4.3 6.4 4.3 1.1 5.3 4.4 2.5 4.35
11.9 5.1 4.3 5.4 6.6 5.3 6.1 4.5 8.4 6.3 6.39
14.9 9.5 2.5
0.71 0 74 0 74 0.70
0.73 0.59 0.67 0.69 0.76 0.69 0.52 0.58 0.73 0.79 0.67
8.3 9.2 6.4 3 8 13.3 4 5 8.35
13.7 15.6 7.5 10.6 11.2 6.1 6.3 8.9 8.1 12.2 10.02
11.0 12.4 5.8 3.1 5.0 4.0 9.7 9.2 3.0 6.1 7.93
0.94 0.94 1.05 1.09 1.17 1.17 1.06
0.94
0.94 0.94 1.09 1.17 1.09 1.17 1.07
0.94 1.17 1.09 1.09 1.09 1.09 1.08
0.94 0.94 1.05 1.05 1.09 1.17 1.04
0.66 0.65 0.62 0.68 0.73 0.77 0.69
0.61 0.69 0.79 0.79 0.72 0.68 0.71
0.77 0.55 0.78 0.85 0.60 0.56 0.69
0.64 0.51 0.61 0.65 0.63 0.79 0.64
0.67 0.58 0.59 0.57 0.56 0.64 0.60
0.67 0.60 0.68 0.71 0.65 0.69 0.67
6.2 5.9 1.5 2.3 3.8 0.6 3.4
4.3 3 5 2.9 1.6 4.7 1.4 3.1
2.5 0.6 1.1 0.9 1.5 2.1 1.5
4.3 3.2 1.7 2.5 4 9 2.0 2.44
3.1 5.6 4.2 3.9 5.5 3.6 4.31
0.94
1.05 1.05 1.09 1.09 1.03
I
0.i5
10.1
834
INDUSTRIAL AND ENGINEERING CHEMISTRY
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another tube to the gas meter. T h e meter was e q u i p p e d with a water manometer which was m a i n t a i n e d at as nearly a constant level as possible. The gases passed from the m e t e r into another tube, which conducted them to the s u c t i o n p u m p . This method of collecting the sample did not permit the complete recovery of all gases evolved during the cooking process, but with the pump drawing vapors at the same rate and under the same head of water, it was believed that the results would be comparative. A f t e r t h e cook was completed, the standard acid solutions from the flask and scrubber were mixed and titrated with standard base. I n experiments 6 to 9, inclusive, the liquid was then poured into a Kjeldahl flask and distilled from caustic solution into a measured q u a n t i t y of standard acid. By titrating this acid solution, the amount of basic compounds in the gases e q u i v a l e n t t o tenth-normal acid was determined. T h e con densate from this Kjeldah1 determination was filtered t h r o u g h activated charcoal and evaporated in order to study t h e basic compounds. These compounds were not identified, but had a c h a r a c t e r i s t i c amine odor. Some of the condensate from the gases was distilled from acid solution in an effort to determine w h e t h e r a n y light oil fractions passed out of the meats. The distillate from this operation did not show the presence of oil, but the condensate from the vapors from the cooker contained some oil which contributed to the acidity as is shown in Table 111. No attempt was made to isolate and identify these acids.
Vol. 23, No. 7
Analytical Methods
The method of determining the percentage of soluble nitrogen compounds in the cakes was as follows: Three and four-tenths grams of the sample were placed in an Erlenmeyer flask and 100 cc. of distilled water added. The mixture was then shaken and immediately placed in a constant-temperature bath a t 40" C. for 30 minutes. While it was in the bath, the mixture was shaken every 5 minutes, after which the solid particles were separated from the liquid by filtration. The nitrogen content of the filtrate was determined by regular Kjeldahl procedure. The results were calculated as per cent ammonia in the cake. The methods for the other analyses were the same as given in the "Rules Governing Transactions between Members of the National Cottonseed Products Association Adopted a t the Thirty-third Annual Session of the Association Held at New Orleans, Louisiana." Results
Table I shows the temperatures at the end of definite increments of time and the rate a t which the temperature was raised to these temperatures. Tables I1 and I11 show the results obtained from the different cooks. From these results it is evident that as the temperature of cooking cottonseed meats is increased the amount of volatile acids is increased. These acids evidently are formed from decomposition of the pectins present. Varying the rate of temperature rise and increasing the time of cooking for 5 minutes do not affect the amount of acid formed unless the temperature is over 101.7" C. (215" F.) when the time is increased. On heating the meats to a high temperature a decided caramel odor is noticed; holding them a t intermediate temperatures for a long time results in the same odor. There is a loss of nitrogenous compounds during the cooking of cottonseed meats, the amount increasing with the temperature. Varying the rate of heating or increasing the time of heating does not affect the amount lost unless the temperature is over 101.7" C. (215' F.), The amount of water-soluble nitrogen compounds decreases with an increase in temperature and length of time of heating. This is due to an increased coagulation of the proteins or to volatilization or both. Conclusion
During the cooking of cottonseed meats there is some decomposition of the nitrogenous compounds and other substances present. The higher the temperature of cooking and the longer the time of cooking, the greater the amount of decomposition. This is evidenced by the increase in the soluble nitrogen compounds present in the cake and the volatile nitrogen compounds in the evolved vapors, and the increase in the amount of volatile acids in the vapors. The ideal temperature of finishing the cooking of cottonseed meats is 107.2" C. (225" F.), and the length of time for the meats to be held at this temperature is less than 20 minutes. United States Exports of Essential Oils to Canada-Canada is the second largest foreign market for American essential oils. Purchases have been increasing steadily in recent years, suffering only a slight recession in 1930. Domestic exports of essential oils to Canada increased in value from $433,784 in 1927 to $488,925 in 1930. In addition t o the regular domestic export trade, there is considerable rdxportation of foreign essential oils from the United States t o the Canadian market. Domestic exports of imported oils t o Canada increased from a value of $65,217 in 1927 t o $107,838 in 1929.
