Study On The Extraction Of Kenaf Seed Oil And Its Oxidative Stability

Kenaf is an annual herbaceous plant,which belongs to Malvaceae family.Kenaf seed is a by-product of kenaf planting and processing with high oil content in kenaf seed,which showed kenaf was a good new oil resources.Kenaf seed was mostly used in the harvest of kenaf plant,in addition to a small amount collection act as seeds,nature fell to the ground and abandoned.Kenaf seeds acted as a potential source of edible oil were usually ignored.The present study was to determin and analysis the major components of kenaf seed and qualities and trace components of seed oils from different cultivars extracted by solvent extraction method.And then,kenaf seed oils were prepared using different solvents,i.e.hexane,ethanol and aqueous enzyme with or without ultrasonic assistance.The components of extracted oils were investigated.What's more,the technology of ultrasonic-assisted extraction of kenaf seed oil was optimized.The changes of components of kenaf seed oils were investigated during the heating process.Firstly,the present study was to determine and analysis the major components of kenafseeds and qualities and trace components of kenaf seeds oils from four different cultivars.The oils were extracted from ground kenaf seed by solvent extraction method.The results showed that the content of crude oil and protein in kenaf seed from four different cultivars were in ranges of 18.52%~21.19%,25.35%~29.57%,respectively..Small differences of four different varieties of kenaf seed oils were found in refractive index,relative density,saponification value,and iodine value.The acid value of kenaf seed oil was ranging from 1.09mg/g to 16.72 mg/g,and the peroxide value was ranging from 0.95 mmol/kg to 2.01 mmol/kg.The main contents of fatty acids were linoleic acid(42.49%~50.28%),oleic acid(27.58%~32.38%),palmitic acid(17.04%~24.25%).The amount of vitamin E of the kenaf seed oils was ranging from 85.81mg/100g to 99.10 mg/100g.The main forms of vitamin E were?-tocopherols and?-tocopherols,which were accounted from 50.82%to 56.03%of the total vitamin E.Sterol contents of the kenaf seed oils were ranging from 199.15 mg/100g to 298.35mg/100g.What's more,?-sitosterol was indicated as the main component,which was accounted from 76.36%to 82.69%.The conspicuous differences were found in?-carotene,phospholipid,and total phenol content of kenaf seed oils of different varieties,which were in ranges of 0~9.66 mg/kg,1.68~4.53 mg/g,5.78~23.22 mg/100g,respectively.Then,kenaf seed oils were prepared using different solvents,i.e.hexane,ethanol and aqueous enzyme with or without ultrasonic assistance.The oil yield,thermal properties,fatty acid composition and minor components(vitamin E,carotene,phosphatide,total phenolic and sterols)of extracted oils were investigated kenaf seed oils oxidation stabilities were explored.Results indicated that the oil yield ranged from 84.71%to 51.12%.Kenaf seed oils showed two major melting peaks at-33.95 ~oC to-31.64 ~oC and-8.57 ~oC to-5.10 ~oC,respectively.Linoleic,oleic and palmitic acid were the major fatty acids in all extracted oils,which accounted for above 96%of the total fatty acids.The type of extraction solvent had a significant influence(p<0.05)on melting profile,fatty acid composition and minor component content of extracted kenaf seed oil.Compared with hexane and aqueous enzyme,ethanol-extracted oil contained more minor bioactive component such as carotene,phosphatide,total phenolic and sterols.Moreover,the oil yield extracted with ultrasound for60 min were equal or even higher than those for 4 h in the absence of ultrasound.The half inhibitory concentrations(IC50 value)of DPPH radical scavenging capacity by different solvents,i.e.hexane,ethanol and aqueous enzyme were 13.993mg/mL,6.319mg/mL and11.192mg/mL,resprctively.The antioxidant capacity was as follows:ethanol extraction,hexane extraction and aqueous enzyme extraction,so as the oxidation stability.More reasonable fatty acid composition and higher content of bioactive components indicated that ethanol extraction with ultrasonic assistance was the most promising alternative method for extraction of vegetable oils.After that,with kenaf seed as raw material,kenaf seed oil was extracted by ultrasonic-assisted solvent extraction.On the basis of single factor experiment,four extraction parameters including ultrasonic time,ultrasonic power,liquid-solid ratio(v/w)and extraction temperature were selected as independent variables,kenaf seed oil yield was investigate value,and ultrasonic-assisted solvent extraction conditions of kenaf seed oil were optimized by orthogonal experiments.The results showed that the optimal extraction conditions were obtained as follows:ultrasonic time 50 min,ultrasonic power 250 W,liquid-solid ratio 9:1 and extraction temperature 35?.Under these conditions,kenaf seed oil yield was 92.03%.The effect of various factors on the oil yield from high to low was as follows:liquid-solid ratio,ultrasonic time,ultrasonic power,and extraction temperature.What's more,kenaf seed oils were prepared using solvent with or without ultrasonic assistance.With the heating process of the two kinds of oil samples,its components were disscussed.During the 24d oven experiments,the peroxide value were presented significant rising trend.With the accelerated oxidation,the content of saturated fatty acid increased gradually and the content of polyunsaturated fatty acid showed a trend of gradually reduce.The melting and crystallization peak temperature of two kenaf seed oils were increased.The vitamin E content of two oil samples in general was on the decline and lost nearly 10%when the experiment finished.Sterol content showed a trend of decline,and the content of solvent extraction oil and ultrasonic assisted extraction oil lost 38.3%and 31.0%,respectively.The content of?-carotene reduced gradually and both the oil samples were undetected at the experiment of 18d.With the accelerated oxidation,the DPPH radical scavenging ability of oils was also gradually reduced.The vintamin E and?-carotene contents of kenaf seed oils were significantly related to the DPPH radical scavenging ability.In conclusion,ultrasonic assisted extraction of kenaf seed oil can effectively improve the oil extraction rate and shorten extracting time,and can also improve the fatty acid compositions of kenaf seed oil and raise the biological active ingredients of kenaf seed oil content.Accelerate oxidation experiments showed that the minor components of kenaf seed oil were reduced,so as the antioxidant capacity.