Strawberry juice colour: The effect of some processing variables on the stability of anthocyanins

The colour stability of juice and purées made from a mixture of two strawberry varieties, stored at + 20°C or at –20°C under aerobic and anaerobic conditions, was studied. High-performance liquid chromatography and spectrophotometric analysis were used to monitor the changes in colour during storage. Pelargonidin 3-glucoside comprised 80% of the total anthocyanin content. Four other pelargonidin-based peaks were found, being 10.4%, 3.5%, 0.7% and 0.3% of the total and two cyanidin peaks were present, being 3.3% and 0.4% of the total. Clarification before storage caused considerable losses in the initial anthocyanin concentrations. Storage conditions (air versus nitrogen) did not influence the rate of loss of anthocyanins during storage or the formation of polymeric pigments. There were no losses in anthocyanins and no increase in the amount of colour measured at 510 nm due to polymers in samples stored at–20°C. Polymerisation occurred in the samples stored at + 20°C, especially in the clarified samples.     

液态挤压在铝合金减震筒上的应用：液态挤压比压值对制件性能影响的分析

指出了压力铸造及热挤压工艺生产铝合金减震筒的缺点，阐述了液态挤压的特征，介绍了液态挤压在减震筒上的应用，分析了比压值对制件性能的影响。     

阶跃信号突变点检测的小波分析法

文章运用小波理论这种新的数学工具,对于由基本平稳的慢变信号和阶跃型突变信号线性组合而构成的这类信号,提出了一种以连续小波变换为主体的检测和分析方法。理论以及实例分析表明,这种方法对于阶跃型突变信号的检侧,是颇为有效的。     

MLS结构的电容-电压特性

本文报导在 Si 衬底上拉制聚酰胺 LB 膜的电容-电压特性,结果表明:它具有与其它绝缘膜相似的特性,为聚酰胺 LB 膜应用于场效应器件奠定了基础。     

NCFW专家系统的汉语接口

NCFW系统是适合于花岗岩与变质岩地区的勘探地下水专家系统，系统的人机交互既可用菜单（亦称项目单）方式，亦可用汉语对话方式。这两种方式既可混合使用亦能灵活切换。本文着重描述了汉语接口的设计思想、实现中采用关键技术以及系统运行实例。     

Tannins/melamine–urea–formaldehyde (MUF) resins substitution of chrome in leather and its characterization by thermomechanical analysis

A new sulfonated melamine–urea–formaldehyde (MUF) resin of relatively low melamine content, prepared according to a sequential formulation, has been shown to be highly effective when coupled with different natural vegetable tannins to produce leather with the same good characteristics of leather prepared with chrome salts. In particular, the antishrinkage effectiveness of the leather prepared according to the new approach is comparable to that obtained with chrome tanned leathers. The comparison of the traditional leather shrinkage temperatures test method with a new thermomechanical analysis (TMA) test method in tension yields thermograms presenting three major modulus of elasticity (MOE) peaks. These are closely connected to molecular level phenomena determining the shrinkage temperature of leather. The three determining parameters appear to be as follows: (1) The average value of the temperatures at which the three MOE peaks occur: the higher the value of this average, the lower is the shrinkage of leather. (2) The average of maximum MOE values of the TMA peaks: the higher this average is, the better is the leather in regard to antishrinkage effectiveness. This means the leather maximum MOE at each peak is a measure of the resistance to the contraction force induced by heat. (3) The relative intensity of the first TMA peak in relation to the second: the higher the value of the MOE for the first TMA peak is in relation to the second peak, the lower the leather shrinkage appears to be. However, it has not been possible to better define or quantify this latter effect. This new TMA test method in tension has also yielded a mathematical relationship correlating the thermogram peak temperatures and MOE averages with the traditional shrinkage temperature to a high degree of confidence. A previous TMA test method, in compression, has proven to yield more problematic and finally not very reliable results when one needs to apply it to a wide variety of different cases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1889–1903, 2003     

Characterization of edible oils,butters and margarines by Fourier transform infrared spectroscopy with attenuated total reflectance

The combination of attenuated total reflectance (ATR) and mid-infrared spectroscopy (MIRS) with statistical multidimensional techniques made it possible to extract relevant information from MIR spectra of lipid-rich food products. Wavenumber assignments for typical functional groups in fatty acids were made for standard fatty acids: Absorption bands around 1745 cm⁻¹, 2853 cm⁻¹, 2954 cm⁻¹, 3005 cm⁻¹, 966 cm⁻¹, 3450 cm⁻¹ and 1640 cm⁻¹ are due to absorption of the carbonyl group, C−H stretch, =CH double bonds of lipids and O−H of lipids, respectively. In lipid-rich food products, some bands are modified. Water strongly absorbs in the region of 3600–3000 cm⁻¹ and at 1650 cm⁻¹ in butters and margarines, allowing one to rapidly differentiate the foods as function of their water content. Principal component analysis was used to emphasize the differences between spectra and to rapidly classify 27 commercial samples of oils, butters and margarines. As the MIR spectra contain information about carbonyl groups and double bonds, the foods were classified with ATR-MIR, in agreement with their degree of esterification and their degree of unsaturation as determined from gas-liquid chromatography analysis. However, it was difficult to differentiate the studied food products in terms of their average chainlength.     

痕量分析中金溶液的稳定性

评述了痕量分析中,金标准溶液和天然水试样中痕量金贮存的稳定性及影响贮存的重要因素,提出了标准溶液配制和贮存的方法。     

用激光测振仪测量扬声器纸盆的振动特性

用激光外差测振装置测量了扬声器纸盆振动幅度与激励电压及激励频牢之间的关系。为扬声器结构及振动特性的研究提供了一种精度高、重复性好的可靠测量方法。