Comprehensive Utilization Of Flaxseed

As a natural functional food material, Flaxseed, which is rich in oil, gum, protein, lignans and other active ingredients, was widely studied. However, it hadn’t yet form the overall planning of the development and utilization of flaxseed process route and the corresponding products in domestic. This research aimed to study the comprehensive utilization of flaxseed processing technology, including extraction of flaxseed lignans and protein, purification of crude extract of lignans and enrichment of alpha linolenic acid, with the aim to maximize comprehensive utilization of the flaxseed and provide theoretical basis for the industrialization process.Firstly, this article screened out the most optimal process routes of comprehensive utilization of flaxseed:pretreatment → extraction of gum through water-extraction and alcohol-precipitation → drying and crushing → extraction of oil through solvent-extraction → degumming and skimmed flaxseed power → one-step extraction of lignans and protein → residue, by adjusting extraction order of the four functional components. One-step extraction of lignans and protein could obtain proteins and lignans simultaneously by leaching with alkaline alcohol solution and acid precipitation. Next, the optimal extraction conditions of one-step extraction of lignans and protein were confirmed (solid to liquid ratio of 1:20, ethanol concentration 40%, alkali amount 0.07 mol·L^-1, temperature 50 °C,2 h, two times) by single factor and orthogonal design experiment. The yields of flaxseed gum, linseed oil, lignans and protein were respectively 9.67%,39.46%,11.03% and 15.27%. The purity of lignans was 28%. The process could obtain several products to realize further comprehensive utilization of flaxseed by merging the extraction of protein and lignans and then reducing the process steps.With the aim to improve the purity of lignans crude products, the adsorption ability of X-5, D101, AB-8 macroporous adsorption resins for lignans was compared. The results showed that X-5 type macroporous resin was the optimum resin. The sample concentration 10 mg·ml^-1) and sample amount（25 ml） were determined by dynamic adsorption and desorption experiments. The effect of two types of elution （gradient elution and isocratic elution） to the purity and recovery of lignans was mainly investigated. The loss rate of elution process using deionized water was 12%. Gradient elution can achieve a variety of products with different purity （for example,30% ethanol fraction showed the highest purity of 85%）, the totle recovery rate of which was 77.63%. The results of isocratic elution indicated that the highest purity of 85% （recovery rate 57.59%） and the highest recovery rate of 75.05% （purity 59.35%） were achieved with 30% and 60% ethanol solutions as eluent, respectively. Prification process of lignans by glucan gel chromatograph was studied with 1.5ml sample amount of lignans crude extract and flow rate of 0.6ml/min. It could obtain two products:the purity of one product was 14.43% （recovery rate 20.14%） and the purity of another was 71.36% （recovery rate 78.22%）. There was almost no loss of lignans in the process with the total recovery of 98.36%. Although the ultimate highest purity was only 71.36% by gel chromatography, the total recovery rate was higher than the method of macroporous resin.It had studied the composition and positional distribution of main fatty acids in flaxseed oil. To obtain higher purity of alpha linolenic acid the research explored two methods, including enzymatic catalytic reaction and freezing crystallization. The main fatty acids were 5.09% palmitic acid,3.32% stearic acid,23.18% oleic acid,15.10% linoleic acid and 53.32% alpha linolenic acid（ALA）. Palmitic acid and stearic acid mainly distributed in Sn^-1,3 position, the fatty acids in Sn-2 position were mainly oleic acid （24.02%）, linoleic acid （21.29%） and ALA （54.69%）, which accounted for 34.19% of total ALA. In the preliminary inquiry of lipase catalysis enrichment of ALA, optimum reaction condition of alcoholysis reaction was:lipase Ls-20, enzyme amount 5%,10 ml n-hexane,2 g oil, mole ratio of oil/alcohol= 1:10, reaction time 48 h. The content of monoglyceride was up to 25.44% and the yield was 76.40%. The fatty acids of monoglycerides mainly were oleic acid, linoleic acid and alpha linolenic acid, with the percentage of 26.248%,21.749% and 51.603% respectively. Although it showed no specific selectivity of lipase in this study to alpha linolenic acid, saturate fatty acids had been removed and the purity of linolenic acid was improved. The effect of lipase catalyzed enrichment for alpha linolenic acid was not ideal, comparing to the enrichment of DHA and EPA, so it was needed for further exploration. It was found that solvent ratio on its enrichment effect is not obvious by freezing crystallization. The purity of alpha linolenic acid could achieve 60% under certain freezing temperature（-30 °C） and freezing time（24 h）.