超临界CO2流体萃取技术提取红花籽油的研究

通过超临界CO2流体萃取红花籽油的试验，研究了物料的粉碎度、萃取压力、萃取温度、萃取时间对红花籽油萃取效果的影响。结果表明，超临界CO2流体萃取红花籽油的最佳工艺条件为粉碎度30目、萃取压强30MPa、萃取温度40℃、萃取时间2h。     

ANALYSIS of BUTTERFAT EXTRACTION and FRACTIONATION USING SUPERCRITICAL CARBON DIOXIDE

A flow through extraction reactor was used to study supercritical fraction-ation of butterfat. the rate of extraction of butterfat was constant for an initial period followed by a decreasing rate of extraction. DSC and GC analyses showed that more soluble triglycerides extracted preferentially in the initial stages exhibited lower melting behavior. the chemical and physical properties of the fractions changed with extraction time. Residual butterfat concentration in the bed was obtained as a function of distance from the bed entrance. the breakthrough curves had a sigmoidal shape, with the ascent-portion of the curves advancing through the bed with the degree of extraction. At the highest extents of extraction, the lower acyl carbon number triglycerides were totally depleted from the lowest portions of the bed, where fresh CO₂ was introduced.     

夹带剂在超临界CO2萃取天然产物中的应用

综述了夹带荆在超临界CO2萃取天然产物中的作用机理、使用方法、夹带剂的种类，以及夹带荆在提取生物碱、酚酸、皂苷、黄酮、脂肪酸等天然产物中的应用。     

EXTRACTION of MILK FAT IN HIGH PRESSURE SOLVENTS

Extraction of milk fat in several high pressure solvents was compared. Solubility of milk fat in supercritical (SC) ethylene and liquid propane was compared to previous results in SC CO₂. At the same operating conditions (temperature and pressure), solubility of milk fat was higher in SC ethylene than in CO₂, although levels generally remained below 5% (w/w). This resulted in significantly higher solubility in SC ethylene when compared at equivalent solvent density. Very little fractionation of milk fat occurred in liquid propane over the range of pressures (3.45 to 5.52 MPa) and temperatures (30 to 90C) studied. Below 77.5C and 2.76 MPa, liquid propane and milk fat were miscible, while a slight fractionation was observed above these conditions. A high pressure sight-gage apparatus was used to visually confirm these conditions for separation.     

MATHEMATICAL MODELING of TRANSIENT HEAT and MASS TRANSPORT IN A BAKING BISCUIT

Drying behavior of a single baking biscuit was modeled using unsteady state, anisotropic, two dimensional, simultaneous heat and mass balances. Solutions of these equations agreed well with the experimentally determined temperature and the moisture data. Modeling revealed that in the outer sections of the baking biscuit conduction and diffusion were the dominant heat and mass transfer mechanisms, respectively. In the central section of the biscuit the gas cells cracked with the increased vapor pressure and the upward volume expansion, then air/vapor enclaves were formed among the horizontal dough layers in the radial direction. the dominant heat and mass transfer mechanisms in the central section of the biscuit were convection. Presence of two different regime zones in a baking biscuit may have important consequences concerning the strength of the commercial products against crumbling during marketing and consumption.     

DISTRIBUTION of HEAT TRANSFER RATE and LETHALITY IN A SINGLE BASKET WATER CASCADE RETORT

Temperature and heat distribution studies were carried out in a single basket horizontal water cascading retort at two temperatures and two air over-pressure levels under fully loaded operating conditions. Various heat transfer parameters (heating and cooling rate indices, f_h and f_c), lag factors (j_ch and j_cc) and process lethality (F_o) were used as indicators of the retort performance. Time-temperature data gathered from 24 Lexan^TM transducers were used for calculation of the heating and cooling rate indices as well as lethality. There were significant variations in the temperature distribution and heat transfer parameters at the different tray levels; however, these variations did not contribute to large variations in the accumulated overall process lethality.     

ESTIMATION of CONVECTIVE HEAT TRANSFER BETWEEN FLUID and PARTICLE IN CONTINUOUS FLOW USING A REMOTE TEMPERATURE SENSOR1

The convective heat transfer coefficient (h_fp) between fluid and particle in continuous tube flow was estimated using a temperature pill, a remote electronic temperature sensor which uses a quartz crystal as the temperature sensing element. the temperature history of a particle (with temperature pill mounted within) was monitored as it moved through a test section. A finite element algorithm was then used to back calculate h_fp from the time-temperature data. the value of h_fp ranged from 134 W/m²K to 669 W/m²K (Nu=3.6 to 17.3) over a fluid generalized Reynolds number range (restricted by experimental constraints) from 19 to 196.8. As expected, h_fp decreased with increasing carrier medium viscosity and increased with increasing flow rates. Even with several conservative factors at play, the lowest Nusselt number was greater than the 2.0 expected for a spherical particle in a stagnant fluid. Potential applications of the technique include noninvasive measurement of the temperature (and h_fp values) of the particles moving within a fluid stream in otherwise inaccessible locations.     

RESIDENCE TIME DISTRIBUTION of CYLINDRICAL PARTICLES IN A CURVED SECTION of A HOLDING TUBE: the EFFECT of PARTICLE SIZE and FLOW RATE1

The residence time and the residence time distributions of cylindrical particles (density 1130 kg/m³ and particle concentration 20% v/v) in a U-bend of 22 cm radius of curvature were studied. All experiments were conducted at room temperature and with an aqueous solution of sodium carboxymethylcellulose (0.5% CMC) as the carrier medium. Two levels of particle size (11 and 20 mm) and three levels of product flow rates (0.66 × 10^?3, 0.81 × 10^?3, and 0.97 × 10^?3 m³/s) were used. the results obtained from this study showed that the mean and the standard deviation of the normalized residence time of particles decreased as either particle size or flow rate was increased. the E(θ) and F(θ) curves indicated that flow profile of particles approached the plug flow profile as the particle size or the flow rate was increased. Results obtained from regression analyses revealed that the mean and the standard deviation of the normalized residence time were significantly influenced by particle Froude number and most strongly by particle-to-tube diameter ratio.