Production of high quality soybean oil and meal: Studies on extraction methods, processing steps, deep-fat frying and optimization of extrusion aided screw pressin

The objectives of this research were to evaluate the effects of extraction methods, processing steps, frying time and optimization of extrusion aided screw pressing on the quality of soybean oil and meal. The Crude soybean oil was obtained by commercial hexane solvent extraction (SE), or extrusion aided screw pressing (EASP) or by low temperature screw pressing (SP) methods. Five gallons of each of degummed, refined, bleached, non-deodorized hydrogenated and deodorized hydrogenated oils were prepared and characterized. The five processed oils were tested for stability against frying times. Optimization of extrusion aided screw press processing variables were performed by the application of Response Surface Methods using Design-Expert software package. The crude soybean oil produced by EASP and SP did not show any significant differences in physical and chemical characteristics compared to the crude oil extracted by SE method. All processing steps did not exert the same effect on all quality parameters, but reduced or increased other parameters. The stability of degummed, refined, bleached, and hydrogenated oils did not only depend on the frying time, but also on the nature of processing. Degummed oil was shown to be more stable than refined or bleached oils but less stable than hydrogenated oils. Two prediction models were produced and a combination of 135 $pm$ 2$spcirc$C temperature, 8.35 $pm$ 1.5% moisture and 10-p-10-8-8 steam lock were found to give the optimum oil yield of 78 $pm$ 2% of commercial grade, and good quality meal with PDI of 24%, 45% protein and a TI value as low as 2%.