Experimental Considerations for Temperature Modulated DSC at Low Temperature

Temperature modulated DSC (TMDSC) at low temperatures requires attention to the selection of experimental parameters that are within the capability of the instrumentation as well as special care in calibration of heat capacity measurement when high precision is required. Data are presented to facilitate selection of appropriate modulation periods and amplitudes at low temperature when using a mechanical cooling accessory. The standard error of the mean heat capacity measurement for a sapphire standard increased with decreasing temperature, decreasing period, and increasing pan mass. For ice in hermetically sealed pans, the standard error of the mean heat capacity measurement was larger than for sapphire and did not follow a predictable trend with changes in temperature and period of modulation. This was attributed to changes in sample geometry between successive measurements due to melting and resolidification. A simple one-point temperature calibration by TMDSC may be unsuitable for precise measurement of heat capacity because of the random error caused by sample placement and the systematic error caused by cell asymmetry, temperature dependence of the calibration constant, and different sample thermal conductivities. An alternative calibration procedure using standard DSC and either a linear or second order fit of the calibration constant over the temperature range of interest is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

鲍鱼中碳、氮同位素的分析

采用真空干燥法对鲍鱼样品进行预处理,通过稳定同位素比率质谱仪测定鲍鱼中碳、氮同位素的含量,测得的平均比率分别为–16.74‰,7.60‰,其相对标准偏差分别为0.02%,0.05%(n=7),表明方法的精密度良好。分析结果得知碳同位素含量主要与其所食用的食物种类有关,而氮的同位素含量不但与食物源和新陈代谢有关,也受气候、环境等方面的影响。     

Kinetics of Atmospheric Freeze-drying of Apple

We present investigations of the effect of Atmospheric Freeze-Drying kinetics on the quality (dehydration rate, shrinkage, color, and antioxidant properties) of apple cubes. The experimental data are compared with the result of convective and vacuum freeze-drying processes, and suitable operating parameters are determined. The experiments were carried out in an Internet controlled, fully automated heat-pump assisted drying system.     

Thermal and FTIR investigation of freeze-dried protein-excipient mixtures

The effect of excipients on the secondary structure of lyophilized proteins was studied through second-derivative Fourier transform infrared (FTIR) spectroscopic analysis. The glass transition temperature (T _g), denaturation temperature (T _d) and moisture content were determined by differential scanning calorimetry (DSC) and thermogravimetry (TG). T _g, T _d and the preservation of protein secondary structure were found to be dependent upon the type and amount of the excipient included in the formulation. Meanwhile, the lyophilized proteins easily adsorbed amounts of moisture during storage to reduce their T _gs and stability.     

Freeze-Dried Complexes of Furosemide with β-Cyclodextrin Derivatives

A freeze-drying method was used to prepare complexes of furosemide (guest) with three derivatives of -cyclodextrin (hosts) in different molecular ratios in order to increase the aqueous solubility and rate of dissolution of the drug, and also to study the influence of this method on different parameters of the guest and the host, such as the diffusion rate constant and the partition coefficient, and additionally the surface tension activity of the host (if any). The hosts were found to have significant, increasing effects on the solubility and the rate of dissolution of furosemide. X-ray diffraction confirmed the host–guest interaction, in support of the earlier results. The freeze-drying method increased the diffusion rate of the drug in complex form, while the partition coefficient varied with the type of -cyclodextrin in the product. It is well known that CD derivatives are highly surface active which gives rise to their hemolytic action. Our observations showed that their presence with furosemide in complex form might decrease (if not diminish) the hemolytic action.     

Structure and properties of polyimide aerogels with different skeleton flexibilities

ABSTRACT

In order to better understand the influences of polyimide (PI) skeleton structure and freeze-drying process on the properties of PI aerogel materials, PI molecular chains (ODPA-ODA, BPDA-ODA, BPDA-PPDA) with different stiffnesses and flexibilities were designed and a series of PI aerogels were accordingly fabricated by freeze-drying technique. The aerogels produced featured light weight (density of 0.01–0.16 g/cm³) and high flexibility, and their density, pore structure, and compress recovery performance could be well controlled by delicately tuning the molecular chain structure and solid contents of the poly (amic acid) salt solution. In addition, a hard PI aerogel with enhanced compressive strength was obtained by quick-freezing in liquid nitrogen.     

Apple Fibers as Carriers of Blackberry Juice Polyphenols: Development of Natural Functional Food Additives

Blackberry polyphenols possess various health-promoting properties. Since they are very sensitive to environmental conditions such as the presence of light, oxygen and high temperatures, the application of such compounds is restricted. Fibers are recognized as efficient carriers of polyphenols and are often used in polyphenols encapsulation. In the present study, the ability of apple fiber to adsorb blackberry juice polyphenols was examined. Freeze-dried apple fiber/blackberry juice complexes were prepared with different amounts of fibers (1%, 2%, 4%, 6%, 8% and 10%) and a constant amount of blackberry juice. Polyphenol profile, antioxidant activity, inhibition of the α-amylase, color parameters, as well as the IR spectra, of the obtained complexes were assessed. The results showed a negative effect of higher amounts of fiber (more than 2%) on the adsorption of polyphenols and the antioxidant activity of complexes. With the proper formulation, apple fibers can serve as polyphenol carriers, and thus the application as novel food additives can be considered.     

The Use of Antioxidant Potential of Chokeberry Juice in Creating Pro-Healthy Dried Apples by Hybrid (Convection-Microwave-Vacuum) Method

The visible trend in the development of the snack market focuses on the use of innovative technologies such as low-temperature or hybrid processes that allow the preservation of native ingredients of raw plant materials. In addition, the high antioxidant potential of, for example, chokeberry fruit can be used to support technological processes and create new products. The aim of the study was to evaluate the possibility of using chokeberry juice concentrate as a component of an osmotic solution to enrich apple samples with natural bio-ingredients and obtain dried apples with increased content of ingredients with antioxidant properties; pro-healthy apple chips. The research material consisted of apples that underwent osmotic dehydration in solutions of sucrose or sucrose and chokeberry juice concentrate and then were dried by the freeze-drying or the hybrid method. The freeze-drying was more beneficial for maintaining the vitamin C content, while the use of the hybrid method resulted in the preservation of more polyphenolic compounds. The sensory evaluation indicated the need to modify the composition of the osmoactive solution. Due to the use of chokeberry juice concentrate, the content of vitamin C, polyphenols, and the antioxidant activity of dried apples was increased.     

Sol-Gel Synthesis of Protoenstatite and a Study of the Factors That Affect Crystallization

Three different magnesium silicate sols were prepared from Mg(OMe)₂ and TEOS for which hydrolysis with H₂O₂ and H₂O was under stoichiometric, stoichiometric, or over stoichiometric. Xerogels were prepared from the sols by simple evaporation, spray-drying, or freeze-drying. The freeze-dried precursor formed mostly protoenstatite, a high-temperature polymorph of enstatite (MgSiO₃) that is generally not stable at room temperature; the other precursors formed mixtures of protoenstatite and clinoenstatite. The three xerogels and their calcined products were studied with XRD, HTXRD, BET, carbon analysis, TG/DTA and²⁹ Si-NMR. Residual carbon was found to be an important factor in the crystallization, and ²⁹Si-NMR spectroscopy was found to be a better tool than XRD to assess the phase purity of protoenstatite.     

顺铂冻干粉的含量测定

建立了顺铂冻干粉注射液含量测定方法的正相高效液相色谱法,色谱条件为:氨基键合硅胶柱,二甲基甲酰胺为样品溶剂,流动相为乙酸乙酯∶甲醇∶二甲基甲酰胺∶水(25∶16∶5∶5,V/V/V/V),在310 nm检测,流速1.5 mL/min,进样量20μL.该法线性相关,相关系数r为0.999 6,回收率为99.6%～100.3%,精确度为0.21%(n=6),最小检出限为59.2μg/L,符合含量测定要求.