Study On Detoxification And Lignans-extraction Techniques Of Flaxseed

Flaxseed is abundant in many nutrients, such as polyunsaturated fatty acid, protein, amino acid and prandial fiber. The recent research proved that flaxseed is also the richest source of lignans. So it was reputed as "functional foodstuff of the 21 century".Because of the existence of cyanogenic glycoside (CG) and other anti-nutritional factors, the application of flaxseed in foodstuff and feedstuff is quantificationally restricted. The aim of this study was to investigate and optimize the detoxification and lignans-extraction technologies, model the process of extraction kinetics, in order to provide some experimental data and a theoretic basis for the development of value added flaxseed products.The detoxification results of 6 kinds of processing methods, including solvent extraction (SE), water boiling, microwave roasting, oven roasting, autoclaving and supercritical CO₂ extraction (SCE), were investigated. According to the water quantity added into the sample matrix, the residual quantity of CGs obtained by methanol, ethanol and isopropanol were reviewed, so, the suitable solvent syetem was determined with regard to economy, safety and lignans recovery, and the optimal parameters for this system were also decided; based on extraction experiments, the optimal temperature, the suitable solvent-matrix ratio and extraction cycle were determined according to the influence of processing parameters on the residual quantity of CGs. The optimal parameters, such as processing temperature and cycle for both oven roasting and autoclaving, were determined by means of examination, analysis and evaluation. The suitable cycle and output power for microwave roasting, the optimal pressure and temperature for SCE were also determined according to the influence of processing parameters on the residual quantity of CGs.SE and SCE methods were introduced to extract lignans from defatted flaxseed flour (DFF). The ethanol was chosen to serve as extraction solvent depending on the extraction effectiveness, and the optimal concentration, temperature and time were determined in terms of lignans recoveries therefrom; hollow-fiber Ultrafiltration (UF) devices was used to clarify the extracion solution and, the osmosis model was established. The ethanol was also chosen as the final modifier in SCE process because it was more effective than tetrahydrofuran. The suitable tret, temperature, pressure and cycle were determined for the SCE method.Based on Peng-Robinson equation of state (PR-EOS), the EOS was established and extracting process was modelled for SCE; derived from Fick' law, the "core shrinking" model for SCE and the kinetic model for SE were established, and the prediction precision of absolute error for the latter was less than 0.7% at all circumstances in this experiment.With the recovery of lignans as experimental indexes, the quadratic orthogonal regression experiments were designed, and the regressive equations concerning the experimental indexes and experimental parameters were obtained for both SE and SCE, what' more, the extraction technology was optimized for SE on the basis of regressive equation. The optimal conditions for SE were ethanol concentration, 68.9⁸2.1 %; extracting cycle, 27²8 h; extracting temperature, 38⁴0℃. Extraction according to the optimal conditions mentioned above, the recoveries of lignans obtained from DFF willreach more than 8% with a possibility of 0.95; the recovery will come to a head of 9.25% with a condition of ethanol concentration 70%, extraction time 28 h and extraction temperature 40℃ obtained by means of statistic excellence-hunt method. According to the influence of experimental parameters on recoveries of lignans for SE, the order of parameters is, extracting time > extracting temperature > ethanol concentration. The optimal conditions for SCE were pressure, 30 Mpa; extracting time, 30 min; extracting temperature, 60℃.The influences of detoxification and lignans-extraction technologies on nutritional components in flaxseed were also investigated and analysed; a stabilization method for...