| Mustard seeds,with high glucosinolate content,is dry seeds of Brassica juncea. The basic chemical structure of GLs is a ?-thioglucoside-N-hydroxy sulfate with a sulfur-linked?-D-glucopyranose moiety and a side chain (R), which determines the class of GLs(aromatic, indolic,and aliphatic).And in the presence of myrosinase or other suitable chemical conditions, GLs can be converted to many degradation products. Recently,with the intensive study of GLs and their degradation products, their health effects have got people's interest and awareness .In this paper, mustard seeds were studied, and the yield of GLs was considered as research aim. First, the optimum extraction conditions of GLs were obtained by optimizing the solvent extraction technology and ultrasonic extraction process. At the same time,comparative of both extraction processes were analyzed by scanning electron microscopy(SEM) to explain the mechanism of increased yield. Then S-8 resin was selected as the purification method, and the adsorption behavior and thermodynamic properties of the resin were investigated. Finally, factors affecting the thermal stability and thermal degradation of GLs in the heating process were also studied. The major concents of the study were as follows:(1)On the basis of single factor tests and BBD design, the optimum extraction parameters obtained finally were as follows: material/liquid ratio (g/ml) 1:25, 50.01? and 50 % ethanol concentration for an extraction duration of 2.01 h, and the yield of sinigrin was found to be 0.0465 %(2)Through the pre-test, cell walls can be destructed by ultrasound, thus improving the extraction rate of sinigrin. After five single-factor tests, ultrasound power and ethanol concentration were identified by Plackett-Burman (PB) design as main factors that influence ultrasound extraction. And the optimal regions were approached by the steepest ascent design. Then regression equation, R1=2.65 + 0.37*A + 0.098*B -0.32*AB -0.15*A2-0.46*B2, was established. The optimal ultrasound extraction conditions were as follows: ultrasound power 300 W, extraction time 25 min, ratio of liquid to solid 15:1(mg/L), ethanol concentration 48%, ultrasound time 4s.Under this optimum condition,the yield was 2.902 %, which was higher than conventional solvent extraction rate.(3)Through the static adsorption and desorption experiments, the S-8 resin was selected. The infrared spectra (IR) was used to analyze mechanism of the adsorption process, and found that they may be combined by hydroxyl group. Then according to the static adsorption kinetics, optimum adsorption time was identified as 75 min. On the basis of the static adsorption experiments, the adsorption isotherm was investigated,and the Freundlich equation was suitable to describe the adsorption process of S-8 resin.Simultaneously, the adsorption process is spontaneously and physically endothermic process.(4)The thermal stability of sinigrin was investigated. The result indicated that high temperatures can accelerate the degradation of sinigrin and the degradation. process is a first order degradation kinetic process. At the same time,the thermal stability can be affected by pH and metal ions. Weakly acidic condition was conducive to the stability of sinigrin. And the exist of Iron(?) has little influence on the thermal degradation, while higher concentration of Iron(?) can affect the degradation of sinigrin to a certain extent .At last, the degradation products were identificated by GC-MS, and the results shows that Allyl-ITC was the main product. |
PDF Full Text Request