A new concept is described for mechanical extraction of oil from soybeans, using dry extrusion as a pretreatment. It was found that coarsely ground whole soybeans at 10 to 14% moisture could be extrusion cooked so that the extrudate emerges from the die in a semi‐fluid state. The dwell time within the extruder was less than 30 seconds, and the temperature was raised to about 135 C. The semi‐fluid extrudate was immediately pressed in a continuous screw press to obtain high quality oil and press cake. Extrusion prior to expelling greatly increased the throughput of the expeller over the rated capacity. An oil recovery of 70% was obtained in single pass expelling using pilot model expellers. Higher recovery rates can be expected with commercial scale expellers. The high temperature‐short time extrusion cooking process eliminates the prolonged heating and holding of raw material in conventional expelling. Under the experimental conditions, press cake with 50% protein, 6% residual oil and 90% inactivation of trypsin inhibitors was obtained. The low fat cake was easily ground in a hammer mill without the usual problems associated with milling of whole beans. The expelled oil was remarkably stable with an AOM stability of 15 hr, which is comparable to refined deodorized oil according to NSPA specifications. The new procedure offers potential for producing natural soybean oil and food grade low fat soy flour by a relatively low cost operation. It may be adopted as an improvement to existing conventional expelling operations in less developed countries or as a commercial or on‐farm operation for producing value added products from soybeans within the U.S.
Two chick growth experiments and a precision-fed cockerel digestibility assay were conducted to evaluate the effect of extrusion and expelling on the nutritive value of conventional (CSB) and Kunitz trypsin inhibitor-free (KFSB) soybeans. In the first experiment, performance of chicks fed CSB or KFSB autoclaved at 121 C was similar to that of chicks fed CSB or KFSB extruded at 138 C. The effect of extrusion temperature on protein quality of the soybeans was evaluated in the second experiment. Eleven corn-soybean diets were formulated to contain one of the following: CSB extruded at 104, 121, 138, or 154 C; KFSB extruded at 104, 121, or 138 C; CSB extruded at 121, 138, or 154 C followed by processing through an expeller; and commercial dehulled solvent-extracted soybean meal (SBM). All diets contained 20% crude protein and the same amount of soybean oil and were fed to chicks from 7 to 21 days of age. The CSB extruded at 104 or 121 C and KFSB extruded at 104 C yielded depressed growth and feed efficiency compared with SBM. Performance of chicks on the other treatments was similar to that of chicks fed SBM. Pancreas weight (as a percentage of BW) decreased as extrusion temperature increased, with the response being greater for CSB. Growth performance was greater and pancreas weights were lower for chicks fed KFSB extruded at 104 or 121 C compared with those of chicks fed CSB extruded at the same temperatures. Expelling improved weight gain and feed efficiency when CSB was extruded at 121 C. A 48-h digestibility assay with cecectomized cockerels indicated that digestibility of amino acids in CSB and KFSB increased as extrusion temperature increased and that digestibilities of amino acids in CSB extruded at 104 or 121 C were lower than those in KFSB extruded at the same temperatures. Results of this study indicated that extrusion of CSB at 138 to 154 C or extrusion of KFSB at 121 to 138 C yields protein quality similar to that of SBM.
Oilseeds occupy an important place in global agriculture by providing vegetable oils and high-protein meals for food, feed, and industrial uses. The leading oilseed crops by volume of world production are soybean, cottonseed, peanut, sunflower, rapeseed (canola), copra (coconut), and palm. The combined world production of these major oilseed crops in [2001][2002] The user has requested enhancement of the downloaded file.
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