Aqueous Enzymatic Extraction Of Corn Germ Oil And Protein Recovery By Nanofiltration

Aqueous enzymatic extraction technology of corn germ oil has been reported in many literatures, however, it could not be applied in industry scale because of its disadvantage such as a large variety of enzymes used, a mass of enzymes added, a long time reaction period and low oil yield. In the dissertation, the optimum technology and mechanism of aqueous enzymatic extraction of corn germ oil have been studied, on the base of this, nanofiltration technology was also applied to recover and purify protein from the hydrolysates, simultaneously, simultaneously,the quality of protein was researched.Above all, the technology of aqueous enzymatic extraction of corn germ oil was developed. Wet corn germ samples were dispersed in water (dry solids/water ratio 1:6 w/v). Citric acid was added and hydrothermal treatment was done by autoclaving at 110?C for 1h. The hydrothermally treated corn germ was milled by the ratio 1:4 (w/v dry solids/water) to get sludge of samples. 2.0% (w/w) of proteinase and 1.5% (w/w) cellulase enzymes were simultaneously added to commence extraction. The hydrolysis was continued at 40?C for 2h followed by an increase to 50?C and continued for another 8h. At the end of the enzymatic extraction, the temperature rose to 80?C and held for 15min to inactivate the enzymes. After centrifugation, the free oil, emulsion, hydrolysates and residues were separated. At the end of the process, the oil recovery was 93.7% of that in the original corn germ. The SEM showed the process of hydrothermal treatment and enzymatic extraction could drastically destroy the structure of corn germ, then the lipid could be released from the tissue of the corn germ.The influence of the aqueous enzymatic extraction technology of corn germ oil on the acid value was studied. The acid value of the original corn germ oil was 5.0mgKOH/g, after hydrothermal treatment, the acid value of the corn germ oil rose to 5.8mgKOH/g, but the acid value of the corn germ oil extracted by the aqueous enzymatic technology was up to 14.3mgKOH/g. The hydrolyzation of the proteinase put a large influence on the acid value of the oil, while the hydrothermal treatment almost had no effect on the acid value of the oil. It was concluded that the acidic proteinase used in experiment could hydrolyze not only peptide linkage but also ester bond, which caused free fatty acid release and the acid value was very high. The cellulase reaction caused the acid value of the oil change a little.The pI of the protein in the citric acid buffer was 5.5, and the citric acid buffer pH was about 4, so the content of soluble protein in the citric acid buffer was very high. Sepharose CL-6B gel-filtration of the soluble protein in the emulsion resulted in three peaks, in corresponding with peaks, the molecular weight (Mw) of the soluble protein focused on 305,562Da, 120,254Da and 75,440Da, during of which, the protein with the Mw of 12,0254Da was the main component, and the proportion of the protein (305,562Da) was relatively low. The emulsification of the protein was different due to its Mw.The NF200-2540 membrane was applied to recover the protein or peptide in the citric acid buffer and hydrolysates according to concentration model. The solution could get concentrated by 3 after nanofiltration, although the effectiveness of salt and acidic removal was poor. The HPLC showed that, during nanofiltration process, the content of the peptide in...