| Rapeseed is an important oil crop of China. The cultivation area of rapeseed is up to 7 million hm2, and the production of rapeseed is more than 12 million tons. The traditional technology of rapeseed oil production is prepress-extraction(PE). PE has many disadvantages that the dark color and poor quality of crude oil, high level of crude fiber in rapeseed cake, the severe denaturation of protein. In order to improve the quality of rapeseed oil and cake, the technology of low temperature pressed de-hulled rapeseed has been gradually developed. The quality of low temperature pressed cake of de-hulled rapeseed(LTPCR) is better, so it is a problem that how to efficiently extract the oil from LTPCR. The technology of n-hexane extraction(NHE) is the first choice to extract the residue oil from LTPCR. But the high temperature in the solvent removal process may lead to the decline of oil’s quality and the severe denaturation of protein. NHE is hard to realize the efficiently utilization of LTPCR. The subcritical extraction technology(SFE) is a newly extraction and separation technology that developed in recent years, which has many advantages, for example, the low extract and desolventizing temperature, high extraction rate and the less destruction of thermo-sensitive ingredients. Currently, SFE has been applied to the extraction of special vegetable oil, essential oil and phenols successfully. But the study of extract oil from LTPCR by SFE has not been reported. In order to achieve the high additional value of LTPCR, this paper study the SFE of oil from zhongshuang-11 LTPCR and the quality evaluation of product. The results are as follows:(1) The influence of pretreatment methods to SFE of oil from LTPCR. At first, LTPCR was treated by four pretreatment methods: flaking, crushing, microwave and puffing respectively. And then SFE will be operated under the following conditions: ratio of solid material to liquid is 1:10, extraction temperature is 40°C, extraction time is 30 min and extract only once. The control group is LTPCR was directly extracted by SFE. The results of experiments show that the oil extraction rate is the highest when the rapeseed cake was crushed to 60 mesh. When compared with the control group, the level of acid value, peroxide value and phospholipid rapeseed oil increased slightly, but when compared with microwave and puffing, the acid value decreased 0.30 and 0.37 mgKOH/g, the peroxide value decreased 0.44 and 0.84 m mol/kg, the phospholipid decreased 2.48 and 5.50 mg/g respectively. The level of Vitamin E, sterol and Canolol are higher than the control group, and increased 7.31 mg/100g、57.28 mg/100 g and 4.83μg/g respectively. Therefore, crushing is the most appropriate pretreatment method for extracting oil from LTPCR by SFE.(2) The optimum experiments of SFE of oil from LTPCR. The results of single factor experiment show that with the increasing of ratio of solid material to liquid, extraction time and extraction times, the oil extraction rate was improved, but the extraction temperature had the contrary effect. The optimum conditions of SFE were obtained by orthogonal text: extraction temperature is 40°C, extraction time is 30 min, ratio of solid material to liquid is 1:8, extract 3 times. The extraction rate was 95.07% at the optimum extraction conditions.(3) The quality evaluation of rapeseed oil that extracted by SFE. SFE was carried out under the optimum conditions, and compared with NHE. The acid value of oil that extracted by SFE was 0.91 mgKOH/g, the peroxide value was 0.65 m mol/kg, the content of phospholipid was 1.22mg/g, which were significantly lower than NHE, and it also conformed to the third level of national standard. The content of micro nutritive components(Vitamin E, sterol and Canolol) were significantly higher than NHE, and the content was up to 97.42mg/100g、698.74mg/100 g and 78.51μg/g respectively. The quality of rapeseed oil that was obtained by SFE is better than NHE.(4) The comprehensive evaluation of SFE. The nitrogen solubility index of defatted meal that was obtained by SFE was the highest, and it was up to 44.77%, which was 8.53% higher than the NHE. The content of glucosinolate, phytic acid, tannin and neutral detergent fiber were 1.28%, 5.64%, 12.21μ mol/g and 26.39% respectively, which were significantly lower than the NHE. SFE needs fewer extraction times, lower extraction and desolventizing temperature to achieve the similar oil extraction rate. The energy consumption of SFE is the 1/3 of NHE. |
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