利用超临界CO2技术萃取红酵母β-胡萝卜素的初步研究水

本研究初步尝试了利用超临界CO2萃取技术从红酵母中提取β－胡萝卜素的效果。结果表明,红酵母经酸-热法破壁后,在所确定的最适萃取条件下（萃取压力30MPa、温度40℃、CO2流量20Kg／h、萃取时间90min）,β－胡萝卜素萃取率可达0．83％。这说明,利用超临界CO2苹取红酵母β－胡萝卜素有一定的可行性,但萃取率较低,对影响萃取的各种因素有待今后深入探讨。     

Lipase-catalysed interesterification between canola oil and fully hydrogenated canola oil in contact with supercritical carbon dioxide

The processing parameters in enzymatic reactions using CO₂-expanded (CX) lipids have strong effects on the physical properties of liquid phase, degree of interesterification, and physicochemical properties of the final reaction products. CX-canola oil and fully hydrogenated canola oil (FHCO) were interesterified using Lipozyme TL IM in a high pressure stirred batch reactor. The effects of immobilised enzyme load, pressure, substrate ratio and reaction time on the formation of mixed triacylglycerols (TG) from trisaturated and triunsaturated TG were investigated. The optimal immobilised enzyme load, pressure, substrate ratio and time for the degree of interesterification to reach the highest equilibrium state were 6% (w/v) of initial substrates, 10 MPa, blend with 30% (w/w) of FHCO and 2 h, respectively. The physicochemical properties of the initial blend and interesterified products with different FHCO ratios obtained at optimal reaction conditions were determined in terms of TG composition, thermal behaviour and solid fat content (SFC). The amounts of saturated and triunsaturated TG decreased while the amounts of mixed TG increased as a result of interesterification. Thus, the interesterified product had a lower melting point, and broader melting and plasticity ranges compared to the initial blends. These findings are important for better understanding of CX-lipid reactions and for optimal formulation of base-stocks of margarine and confectionary fats to meet industry demands.     

牡丹籽油超临界CO2萃取工艺优化及抗氧化活性的研究

以牡丹籽为原料,利用超临界CO2萃取法提取牡丹籽油。采用单因素试验对影响牡丹籽油萃取率的3个因素(温度、压力和时间)进行了考察;以萃取率为响应值,以温度、压力和时间3个主要影响因素设计正交实验(L9 33),对提取条件较为温和、对油脂抗氧化性成分破坏较小的超临界提取工艺进行了优化;采用DPPH法和亚铁离子(Fe2 )诱导的过氧化体系法,以油酸和亚油酸为对照,研究了压榨法和超临界CO2萃取法两种工艺提取的牡丹籽油清除DPPH自由基和抗脂质过氧化能力的差异。结果表明,萃取时间对萃取率影响最大,其次为萃取温度,萃取压力对萃取率影响最小;超临界CO2萃取法提取牡丹籽油的优化工艺条件为：温度35℃、压力30 MPa、时间60 min,牡丹籽油的萃取率为28.86%;牡丹籽油的抗氧化性质与脂溶性抗氧化剂类似;超临界油清除DPPH自由基的能力明显高于压榨油,而经Fe2 诱导的脂质过氧化程度则低于压榨油,说明超临界CO2提取的牡丹籽油品质优于压榨油,建议采用超临界CO2萃取技术提取高附加值牡丹籽油。     

Effects of supercritical carbon dioxide extraction conditions on yields and antioxidant activity of Chlorella pyrenoidosa extracts

Yields and antioxidant activity of Chlorella pyrenoidosa extracts obtained by supercritical carbon dioxide extraction through an orthogonal experiment (L₁₆(4⁵)) were investigated to get the best extraction conditions. The results showed that extraction pressure, temperature and modifier were the main three variables that influenced the yields of extracts. The highest yield was obtained at 32 °C, 40 MPa, 20 L h⁻¹ with dosage of modifier 1 mL ethanol g⁻¹ sample for 3 h. Moreover, increasing pressure and concentrations of modifier led to the increase of extraction yields and antioxidant activity. DPPH radical scavenging method showed that almost all the extracts had significantly higher antiradical activities varying from 29.67 ± 0.29% to 54.16 ± 4.49% comparing to -tocopherol, Trolox, and BHT as references except extracts at 32 °C, 35 MPa and 15 L h⁻¹ without modifier for 1.5 h. These results indicate that supercritical extraction is a promising alternative process for recovering compounds of high antioxidant activity from C. pyrenoidosa.     

Supercritical fluid extraction of fish oil from fish by-products: A comparison with other extraction methods

Fish and fish by-products are the main natural source of omega-3 polyunsaturated fatty acids, especially EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), both of them with a great importance in the food and pharmaceutical industries. Comparing to conventional fish oil extraction processes such as cold extraction, wet reduction or enzymatic extraction, supercritical fluid extraction with carbon dioxide under moderate conditions (25 MPa and 313 K) may be useful for reducing fish oil oxidation, especially when fish oil is rich in omega-3 such as salmon oil, and the amount of certain impurities, such as some species of arsenic. Furthermore, taking profit of the advantages of supercritical carbon dioxide as extractive solvent, a coupled extraction-fractionation process is proposed as a way to remove free fatty acids and improve fish oil quality, alternatively to physical and chemical refining procedures.     

超临界水氧化技术处理2-萘酚废水的研究

2-萘酚是严重污染环境和危害人体健康的有害物质,目前采用传统废水处理方法,很难将其彻底去除.超临界水氧化技术是一种新兴废水处理技术,能够对许多传统方法难以去除的有机废水进行有效处理.对含2-萘酚废水的超临界水氧化降解进行了研究,主要讨论了温度、压力、停留时间等因素对反应的影响,2-萘酚的降解率随着这3个因素的升高而升高...     

Inactivation of polyphenol oxidases in cloudy apple juice exposed to supercritical carbon dioxide

The inactivation of polyphenol oxidase (PPO) in cloudy apple juice exposed to supercritical carbon dioxide (SCCO₂) treatment was investigated. Higher pressure, higher temperature, and longer treatment time caused more inactivation of PPO. The maximum reduction of PPO activity reached more than 60% at 30 MPa and 55 °C for 60 min. The experimental data followed first-order reaction kinetics; the kinetic rate constant k and the decimal reduction time D were closely related to the pressure and temperature of SCCO₂ treatment. Higher pressures or higher temperatures resulted in lower D values (higher k), the D value of PPO was minimized to 145 min treated by the combination of 30 MPa and 55 °C. Activation energy of 18.00 kJ /mol, was significantly reduced by SCCO₂ treatment at 30 MPa, as compared to activation energy of 72.0 kJ/mol for identical treatment at atmospheric pressure. Pressure and temperature sensitivity of kinetic parameters were studied. Z_P at 55 °C was 66.7 MPa and Z_T at 30 MPa was 108 °C.     

SUPERCRITICAL AND SUB-CRITICAL FLUID SOLVENT EFFECTS ON A DIELS-ALDER REACTION

The effect of pressure on the measured bimolecular rate constant of the Diels-Alder reaction between maleic anhydride and isoprene was investigated in supercritical CO₂ and sub-critical propane. The reaction was carried out at 35°C in CO₂ and 80°C in propane. Measured bimolecular rate constants are also compared to predictions from the thermodynamic pressure effect using transilion state theory and the Peng-Robinson equation of state. The rate constants in supercritical C0₂ agreed closely with the thermodynamic pressure effect predictions over the entire pressure range. Furthermore, the mole fraction based rate constants were found to vary linearly with the density of the solution. The rate constants in the sub-critical propane solvent significantly diverged from the thermodynamic pressure effect predictions and were found to deviate from this linear density dependence at the lower pressures studied. The results are interpreted in the context of local reactant concentrations about the reacting maleic anhydride and solvent-solute and cosolvent-solute interactions.     

Generation of chitosan nanoporous structures for tissue engineering applications using a supercritical fluid assisted process

In recent years, considerable attention has been given to chitosan-based materials and their applications in the field of tissue engineering. However, the techniques proposed until now for the formation of chitosan scaffolds present some limitations such as: they are very time-consuming, use organic solvents, have difficulties in the obtainment and preservation of various levels of porosity and the 3-D structure. In this work, a new SC-CO₂ assisted process for the production of chitosan scaffolds is proposed; it consists of three steps: formation of a chitosan hydrogel by thermally induced phase separation; substitution of water with a suitable solvent; drying of the gel using SC-CO₂. Using this process, we produced chitosan nanostructured networks with filaments diameters around 50 nm, without any collapse of the gel nanostructure, characterized by a high porosity (>91%) and high compressive modulus (150 kPa).     

Continuous synthesis of Zn2SiO4:Mn fine particles in supercritical water at temperatures of 400-500 °C and pressures of 30-35 MPa

Sub-micron sized Zn₂SiO₄:Mn²⁺ phosphors particles were continuously synthesized in supercritical water with a flow reactor. Colloidal silica or sodium silicate was used as the Si source. Zn and Mn sources were chosen from their nitrates, sulfates, and acetates. The syntheses were carried out at temperatures from 400 to 500 °C, at pressures from 30 to 35 MPa, at NaOH concentrations from 0.014 to 0.025 M, and for residence times from 0.025 to 0.18 s. Sodium silicate formed α- and β-Zn₂SiO₄:Mn²⁺ phases regardless of the Zn and Mn sources, while colloidal silica formed phases dependent on the type of Zn and Mn sources used in addition to the use of alkali. As the reaction temperature increased, the crystallinity of α-Zn₂SiO₄:Mn²⁺ phase increased and the Mn substitution into the Zn sites of the α-Zn₂SiO₄ phase decreased. Of the conditions studied, the most highly crystalline α-Zn₂SiO₄:Mn²⁺ was produced at a temperature of 400 °C, a pressure of 30 MPa, a NaOH concentration of 0.14 M, and a residence time of 0.13 s with Zn and Mn sulfates and colloidal silica as starting materials. The α-Zn₂SiO₄:Mn²⁺ fine particles synthesized were round in shape, had an average diameter of 268 nm, and exhibited a green-emission with a peak wavelength of 524 nm.