Effect of prepressing conditions before extraction on the quality of corn oil and residue
1990
Sitima Jittinundana
Four levels of screw-press pressure were studied for pressing wet-milled corn germ which had oil content of 53.51 percent on dry weight basis. After pressing, the oil remained in prepressed corn germ was 43.68, 40.48, 37.08 and 34.30 percent on dry weight basis, respectively when pressure was increased from level 1 to level 4. The higher screw-press pressure, the darker yellow color of the prepressed corn oil. Prepressed corn oils, in the order of increasing pressing, contained 5.12, 5.40, 5.82 and 6.25 percent free fatty acid. High pressure pressing, resulted in powder, while low pressure pressing, resulted in flake. Free oil contents in prepressed corn germ were 5.0, 8.3, 10.1 and 10.6 grams per 100 grams of corn germ, respectively with increasing levels of pressing. Oil extraction times with normal hexane to reduce oil content to less than 1.5 percent for prepressed corn germs with oil contents were 120, 90, 45 and 30 minutes, respectively. High pressure pressed corn germ had higher rate of oil extraction than low pressure pressed one. Nitrogen solubility indexes of prepressed-solvent extracted corn germ meals were 26.63, 24.36, 22.16 and 21.40 percent, respectively. No significant differences in chemical and physical properties of refined corn oils. Refined corn oils had a light yellow and good aroma and contained 82 percent unsaturated fatty acids which composed of 35 percent oleic acid, 46 percent linoleic acid and linolenic acid less than 1 percent.
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