Mechanisms that control the extraction rate of essential oil from Zataria multiflora Boiss. (Z. multiflora) with subcritical water (SW) were studied. The extraction curves at different solvent flow rates were used to ...Mechanisms that control the extraction rate of essential oil from Zataria multiflora Boiss. (Z. multiflora) with subcritical water (SW) were studied. The extraction curves at different solvent flow rates were used to deter-mine whether the extractions were limited primarily by the near equilibrium partitioning of the analyte between the matrix and solvent (i.e. partitioning thermodynamics) or by the rates of analyte desorption from the matrix (i.e. ki-netics). Four simple models have been applied to describe the extraction profiles obtained with SW: (1) a model based solely on the thermodynamic distribution coefficient KD, which assumes that analyte desorption from the ma-trix is rapid compared to elution; (2) one-site kinetic model, which assumes that the extraction rate is limited by the analyte desorption rate from the matrix, and is not limited by the thermodynamic (KD) partitioning that occurs dur-ing elution; (3) two-site kinetic model and (4) external mass transfer resistance model. For SW extraction, the thermodynamic elution of analytes from the matrix was the prevailing mechanism as evidenced by the fact that ex-traction rates increased proportionally with the SW flow rate. This was also confirmed by the fact that simple re-moval calculations based on determined KD (for major essential oil compounds) gave good fits to experimental data for flow rates from 1 to 4 ml·min-1. The results suggested that the overall extraction mechanism was influenced by solute partitioning equilibrium with external mass transfer through liquid film.展开更多
以藕渣为原料,采用亚临界水萃取(Subcritical water extract ion,SWE)技术结合醇沉淀法制备藕渣中可溶性膳食纤维(Soluble dietary fiber,SDF),优化SDF的SWE工艺,并与常规热水提取(Hot water extraction,HWE)法比较。结果表明,SWE藕渣中...以藕渣为原料,采用亚临界水萃取(Subcritical water extract ion,SWE)技术结合醇沉淀法制备藕渣中可溶性膳食纤维(Soluble dietary fiber,SDF),优化SDF的SWE工艺,并与常规热水提取(Hot water extraction,HWE)法比较。结果表明,SWE藕渣中SDF的最佳工艺为:盐酸体积分数10%、萃取温度140℃、萃取时间16 min,料液比1:20(g/mL),此条件下藕渣SDF的萃取得率为40.80%,较HWE法SDF的得率提高16.8%。在一定浓度范围内,SWE的SDF的还原能力、对DPPH·和ABTS^+·的清除能力均弱于HWE的SDF,这可能与SWE使SDF得率提高,导致具有抗氧化活性的SDF成分含量相对降低或活性破坏或形成具有其它活性的SDF成分有关,其具体机制有待进一步研究。SWE藕渣SDF在萃取时间和得率上均较HWE占有较大优势,是一种SDF高效萃取的潜在方法。展开更多
基金support is gratefully acknowledged to the Semnan University and the Iranian Research Organization for Science and Technology (IROST)
文摘Mechanisms that control the extraction rate of essential oil from Zataria multiflora Boiss. (Z. multiflora) with subcritical water (SW) were studied. The extraction curves at different solvent flow rates were used to deter-mine whether the extractions were limited primarily by the near equilibrium partitioning of the analyte between the matrix and solvent (i.e. partitioning thermodynamics) or by the rates of analyte desorption from the matrix (i.e. ki-netics). Four simple models have been applied to describe the extraction profiles obtained with SW: (1) a model based solely on the thermodynamic distribution coefficient KD, which assumes that analyte desorption from the ma-trix is rapid compared to elution; (2) one-site kinetic model, which assumes that the extraction rate is limited by the analyte desorption rate from the matrix, and is not limited by the thermodynamic (KD) partitioning that occurs dur-ing elution; (3) two-site kinetic model and (4) external mass transfer resistance model. For SW extraction, the thermodynamic elution of analytes from the matrix was the prevailing mechanism as evidenced by the fact that ex-traction rates increased proportionally with the SW flow rate. This was also confirmed by the fact that simple re-moval calculations based on determined KD (for major essential oil compounds) gave good fits to experimental data for flow rates from 1 to 4 ml·min-1. The results suggested that the overall extraction mechanism was influenced by solute partitioning equilibrium with external mass transfer through liquid film.
文摘以藕渣为原料,采用亚临界水萃取(Subcritical water extract ion,SWE)技术结合醇沉淀法制备藕渣中可溶性膳食纤维(Soluble dietary fiber,SDF),优化SDF的SWE工艺,并与常规热水提取(Hot water extraction,HWE)法比较。结果表明,SWE藕渣中SDF的最佳工艺为:盐酸体积分数10%、萃取温度140℃、萃取时间16 min,料液比1:20(g/mL),此条件下藕渣SDF的萃取得率为40.80%,较HWE法SDF的得率提高16.8%。在一定浓度范围内,SWE的SDF的还原能力、对DPPH·和ABTS^+·的清除能力均弱于HWE的SDF,这可能与SWE使SDF得率提高,导致具有抗氧化活性的SDF成分含量相对降低或活性破坏或形成具有其它活性的SDF成分有关,其具体机制有待进一步研究。SWE藕渣SDF在萃取时间和得率上均较HWE占有较大优势,是一种SDF高效萃取的潜在方法。
