EXPRESSION OF VEGETABLE OILS A General Equation on Oil Expression EUGENE C. IC00 National Bureau of Industrial Research, Ministry of Economic Affairs, China
meal immediately before and Based upon experimental data on the exafter pressing. In the fourth aspects of the processes pression of seven kinds of oil seeds (soybean, series of runs only the moisture involved in the oil excottonseed, rapeseed, peanut, sesame seed, content in the meal was varied pression (mechanical extractung nut, and castor bean), the following throughout the steaming and tion) have been studied by general equation is found to be applicable cooking. The seven kinds of Better and Munk ( 2 ) ,Woolrich oil seeds studied are given in and Carpenter ( l a ) ,Kolpakov (on the dry basis) : Table I. and Pasmanik (9), Heublyum Typical experimental data and Japhe (7), and others; w = cwo dP47$6on the effects of pressure, pressure, temperature, moistime, temperature, and moisture, and pH are the factors where W is the oil yield; C, a constant for ture content on oil yield durmentioned which affect the ing the expression of cottonone kind of oil seed; Wo,the oil content of processes. Goldovskii ( 4 , 5 , 6 ) seed are given in Tables I1 advanced and proved a physicothe Geed; P , the pressure; 6, the pressing to V. After delinting, hulling, chemical theory of oil exprestime; v, the kinematic viscosity of the oil and steaming, the cottonseed sion. Jamieson (8)stated that at press temperature; and z, the exponent used contained 31.72 per cent 8-9 per cent moisture in the on viscosity factor varying from 1/6 to 1/2. oil and 8.2 per cent water. meal will give good press room The moisture content of the The press efficiency during expressing can results; however, Beisler ( 1 ) meal was kept constant a t found that in the pressing of be calculated from ( W / W o ) . Experimental 8.2 per cent during the runs tung nut the moisture content data reveal that for one kind of oil seed duron the effect of pressure, should not exceed 6 per cent. ing expression there is an optimum range temperature, and time. From Taylor (11) showed that inof moisture content for maximum oil yield. constants kj, k2, (Tables 11, creasing the percentage of 111, and IV) the following Of the various oil seeds studied, this range water in cottonseed by presequation is proposed for the sure cooking above 129.5' C. varies from 5 to 13 per cent. expression of cottonseed: increases the oil yield by 0.46 oer cent. However. no exact ;elation appears in the literature for the various factors which affect oil production during expression. Previous papers (10) reported studies on the expression of seven kinds of oil seeds found in China. Pressure, temperaTable IV (effect of moisture content on oil yield) shows that ture, pressing time, and moisture content are the factors there is an optimum range of moisture content during expreswhich affect oil yield. The present article summarizes the sion. At 18' C. this optimum is 6-11 per cent moisture; previous studies and presents a general equation which states at 100" C. the range is 8-13 per cent (Figure 2 and Table IV). the relation of the common factors in expression. Complete data on the effect of the four variables on oil yield for the six other oil seeds were obtained, and their individual constants were calculated. Pressure, temperature, and time Experimental data for the optimum range of moisture content found exA laboratory hydraulic press similar to the Carver model perimentally are listed in Table VI. According t o these (3) was employed. It has 6 X 6 inch pressing surfaces, bestudies the following empirical equation can be ufied to express tween which a maximum pressure of 5000 pounds per square inch can be obtained by a hand-operated oil pump. Electric hot plates were provided for heating when the temperature effect was being studied. Four hundred t o six hundred grams TABLE I. DESCRIPTION OF OIL SEEDS of oil seed were used for each run. The samples were hulled, Common Origin in Botanical decorticated (and delinted in the case of cottonseed), and Name China Family Genus and Species ground t o the desirable uniform size. Cooking and steaming Leguminosae Glycine soja S. and Z. Soybean Nanking brought the moisture content of the meal up to a higher value Nanking Malvaceae Gossypium P. Cottonseed Brassica juncea Chungking Cruciferae Rapeseed than that of the original sample and this moisture content Leguminosae Arachis hypogaea L. Peanut Chungking was kept constant throughout the first three series. I n these Tung nut Chungking Euphorbiaceae Aleurites fordii Hemsl. runs the effects of pressure, temperature, and time were tested Sesamum indioum L. Sesame seed Chungking Pedaliaceae by varying one factor a t a time. The oil yield in weight per Euphorbiaceae Ricinus communis L. Castor bean Nanking cent was calculated from the difference in the weight of the 342
HE p h y s i c o c h e m i c a l
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I N D U S T R I A L ANI) E N G I N E E R I N G CHEMISTRY
March, 1942
Since on the dry basis Equation 2 becomes
TABLE11. EFFECT OF PRESSURE ON OIL YIELD OF COTTONSEED (T 18O C.; 6 = 4 hours) P, Lb./Sq. In. z/F ki 2000 44.7 2500 50.0 3000 54.7 3500 59.2 4000 63.2 Average
pw W;2 = K a ,
3
W,, Wt. % 10.03 11.25 12.16 13.10 14.00
= W/
