Soy-Bean Oil Quality and Yield as Affected by Conditions o f Expression R. L . SMITH AND H. 11. K ~ ~ ~ Y B I'urdue I L L , University Agricultural b'xperiment Station, Lafayette, Ind.
A
PI'ARENTLY the first soy beaus were int r o d u c e d int.o the United Statesin 1804. At t h a t t i m e t h e y were regarded as a botanical c u r i o s i t y and it was not until recent years that the s o y - b e a n industry (i e v e lo p e d ex t e n sively. According to Morse ( 2 ) the first soy beans m i l l e d in tliia c o u n t r y were pressed in a cottonseed-oil mill in North Carolina i n 1913. The p r o d u c t i o n of soy-bean oil and soyiiean Oil has increased very much in the last five v e a r s .
EXPELLERS USEDIN P ~ o ~ u c i nSOY-BEAN o OIL AND MEAL BY PROCESS
is the leading state in soy-bean production; with North Carolina second and Indiana third. Soybean oil is used oolnmercially for a wide variety of purposes: in paints, varnishes, lacquers, linoleum, waterproof fabrics, core-binding oils, soaps, etc. Soy-bean oil is also finding considerable use today as an edible oil. For many purposes, particularly in the manufacture of paints and varnishes, a "nonbreak" soy-bean oil is desired. A "nonlireak" soy-bean oil is one that when heated to a temperature of approximately 600" I?. shows little or no precipitate and bleaches to a colorless or a very pale yellowisli colored oil. The soy-bean oil that is produced today by passing the beans through expellers or hydraulic presses when heated to 600" F. develops a dark color and a dark colored precipitate. This oil is known as a "brea.k" oil.
D a m m ~ nSor B s n m O.OPESCliNT LIOISTORE
Color oi Oil
iodine No. Oil
1lC.
'Txlit.. PnEsSE"
noom
"452 50 55
60 65
70 75 80 85
90 95 1W
,
-
_
_
Oil
ne-
teat
teat
tcst
311
10 5
i:s2.5 133.6 134.0 138.3 133.6 134.1 134.8 133.9 131.4 132.6 133.8 132.9 134.0 131.8
iP*!I
35
a5 40 40 35 40 45 45
50 55 00 50 60
5
10
10
15 40
45 55 65
80 85 100 100
irrt
test
:xu
9 5 5 10 10
127.0 :3S 127.8
:35
127.7
35
128.4 40 129.8 40 130.0 45 127.9 40 127.5 4 6 128.8 45 128.7 45 126.5 45 12R.0 45 1 2 6 3 55
20
16 30
:la 45 51)
76
no
85
-
hh'XHDS
d quantity of soy beans was grtiund fine enough to pass tlirougli a 2-mm. sieve and dried in the vacuum oven a t a temperature of 48" to 50" C. The various moisture contents were obtained by placing a weighed quantity of the nical in a desiccator and adding to the desiccator the required amount of water. The ground soy beans were then permitted to remain in t,he desiccat.or with occasional stirring until the moisture had become uniformly distributed throughout the sample. The samples of soy heaxis of known moisture contents were jiressed in the laboratory hydraulic press and the temperatiires were controlled by means of hot plates above and beknv the cylindrical press. The temperature on the inside
~
test
Color of iodine No. Oil Oil lle?.tier lore After Ilcfixe After break brank break break break toni ,?at test teat test
M 2 . 0 125.7 i a s . 7 128.6 131,8127.9 132.6 126.8 1:35.3 126.3 132.3 126.7 135.2 127.6 135.2 127.0 134.2 lZ5.!l 132.8 128.6 lS3.6 127.6 132.2 1 2 6 . 6 132.0 1 2 7 , o 134.0 P26.2
B PBiiCYiYT JdOlYTOBE
8 PBK CINT Y",bll"RE Color of iodine No.
Color of Oil Be-
Iodine No.
tea,
,,%It
test
test
teRC
test
10 'IS 40 40 40
5
1:i24 13X.6 l34:I 1a4.0 13:i.i 131.2 181.7 133.4 133.3 181.1 136.0
128, 128.C 128.5 127.u 127,s 127.7 P2R.1
35 40 40 46 40 40
10 10 25 43
Oil
fnie Aft,ei Befoia After break break break break
35 40 40 45 45 45
50 55
65
334
__
I \ ~ N C B VSor B m n s
I P 1 R CBNI % r O I I ~ " B E
Iodine No Oil
ioie Aftar Before .After fore Alter Liefore bieakbieak break break bioaklwerrk break test
_
0 . 8 P B " CBNT YOmTvBe
Color of
It has been known for s o m e t i m e that when the beans are pessed cold without heating, a nonbreak oil may be obtained. In commercial practice, h o w e v e r , the yield o b t a i n e d is m u c h lower if t h e beans are pressed without heating. At the p r e s e n t time ill commercial practice the beans are heated a t temperatures above 100"C. Since the quality of the soybean oil is impaired by pressing at high temperatures, it EXPEI,LEH seemed worth wliile to s t u d y t h e effect of moisture content uird
5 5
6 1.5 25 45
7s
100 106 110 110 iin 110
Me
Oil
break break break
35
I ~ ' I 40
127.4 128.4 127.7 U2.o 129.0 i:i3.1 127.8 1:i1.2 128 L
Oil
fore After Before
40
35 40 55
65 65
5 5
50 75 100
105 105 110 110 110
teet
1JO.6 132.4
After
break test
127.0 127.5
134.9 132.8 1'31.9 133.1 131.3 152.6
128.%
132.2
128.0 127.9 128.3 127.4
129.1
128.0
127.1 127.6 l28.S 131.1 128.6 134.2 1 2 7 . 4
134.0 182.9 133.4
March, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
335
ferent conditions. The figures given for color of the oils represent the number of milligrams of iodine in the iodinepotassium iodide solution which matched the color of the oil when equal depths of the two liquids were compared. Changes in moisture content and temperature of pressing of the soy beans did not affect the iodine number of the oil Heating the oil during the break test lowered the iodine number of the oil in all instances. When pressed dry, the results with the two varieties of soy beans were very similar. At temperatures of 55" C or below, the color of the oil after the break test was similar to that pressed a t room temperature after the break test, but when the temperature was raised above 55" C. there was an increase in the color of the oil after the break test. When the temperature of pressing reached 60" to 65" C., there was a rapid increase in the color of the oil after the break test. With Manchu soy beans containing 4 per cent of moisture, a satisfactory nonbreak oil was produced by pressing a t 65" C. With moisture contents of 6 and 8 per cent the
of the cylinder was taken before pressing by means of a thermometer inserted in the sample. The actual time required for pressing the sample was 2 hours. For the first 30 minutes the pressure was kept a t approximately 5000 pounds per square inch. The pres-
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