酸乳中有机酸检测方法的研究进展

有机酸是酸乳中的重要指标.对有机酸的研究,不仅可以了解发酵的代谢背景,调控有机酸的产生,同时也对评价酸乳的营养价值、口感风味和研究其生理功能有重要作用.简要介绍酸乳中有机酸分离与定量的毛细管电泳法、离子色谱法、气相色谱法以及高效液相色谱法的步骤及其优缺点.     

PASTEURIZATION DESIGN CRITERIA FOR PRODUCTION OF EXTENDED SHELF-LIFE REFRIGERATED LIQUID WHOLE EGG

Pasteurization schedules of liquid whole egg are designed for inacti-vation of pathogens. Postprocess contamination and survival of heat resistant spoilage bacteria make it necessary to keep the product frozen for extended shelf-life. In this study, criteria required for production of a refrigerated pasteurized liquid whole egg are discussed. Pasteurization schedules which yield up to 5% soluble protein loss are suggested as the highest level of heat treatment. A combination of such heat treatment and aseptic packaging is suggested as a potential route for production of a long shelf-life pasteurized liquid whole egg.     

红提葡萄中有机酸成分的GC-MS分析

为研究葡萄中的有机酸成分，将葡萄有机酸提取、酯化后，采用GC—MS分析葡萄中的有机酸，研究表明，葡萄中含有17种有机酸，其中多元酸7种，饱和脂肪酸5种，不饱和脂肪酸4种，此外，还包括1种氧代有机酸。     

AN IMPROVED METHOD OF CHOLESTEROL DETERMINATION IN EGG YOLK BY HPLC

An improved method for cholesterol determination in egg yolk is reported in this paper. Egg yolk was first diluted. Cholesterol was then extracted with ether and petroleum ether, and quantified by reverse phase chromatography on a Zorbax ODS column (0.46 × 15cm, 5–6 μm) using a mobile phase of acetonitrile and 2-propanol (4:1) with a flow rate of 0.6 mL/min. A linear correlation was observed between cholesterol concentration at 0.05–0.40 mg/mL and its peak heights with a correlation coefficient of 0.9993 (n = 5). The average recovery was 98.9%, and detection limit was 0.02 mg/mL. No differences in cholesterol concentration were observed between egg yolk samples with and without saponification. Rapid and reproducible quantification of cholesterol in egg yolk can be completed with this simplified method.     

果品中有机酸提取方法比较研究

以新疆地产四种特色果品为试验材料，采用蒸馏水水浴、蒸馏水超声、80％乙醇匀浆、80％乙醇超声等分别提取有机酸，并通过反相高效液相色谱法同时测定。结果表明，不同的提取溶剂和提取工艺对4种干鲜果品中各种有机酸的提取效果有一定影响，其提取的种类和含量有一些差异。综合考虑试验步骤和结果等各方面因素发现，80％乙醇匀浆提取方法既能有效保证有机酸的提取种类和提取数量，又能大大简化试验步骤。     

ORGANIC ACIDS AND GLYCEROL IN BEER

The concentrations of pyruvic acid, citric acid, L-malic acid, acetic acid, L-lactic acid and glycerol were determined in beers of different type and origin. Large differences in organic acid and glycerol contents were found, especially between different types of beer. The amounts of acetic acid, lactic acid and glycerol can be used as process parameters. During malting a decrease of the malic acid-citric acid ratio occurred due to the pathway of the TCA-cycle. The acetic acid content and glycerol contents showed increases during fermentation. The latter parameter is useful to indicate if alcohol-free beer has been produced by fermentation. Determination of apparent final attenuation degrees of worts according to the usual laboratory practice resulted in higher glycerol contents than was found for the corresponding beers, making the value of this assay questionable.     

卡尔曼滤波分光光度法的改进及对Mo,W含量的同时测定

对卡尔曼滤波分光光度法中的吸光系数矩阵的建立作了改进，引入非零截矩（或交互作用）项，并用常规方法与改进方法处理Ｍｏ，Ｗ二组分体系．结果表明，改进方法在一定程度上校正了多组分之间的相互作用，比常规方法具有更强的适应性     

PULSED ELECTRIC FIELD TREATMENT OF LIQUID WHOLE EGG INOCULATED WITH SALMONELLA ENTERITIDIS

The effects of pulsed electric fields (PEF) on the inactivation of Salmonella Enteritidis inoculated into liquid whole egg (LWE) and on the physical properties and the shelf-life of LWE were studied. PEF processing conditions were 1.2 mL/s flow rate, 200 pps frequency, 2.12 μs pulse duration, 25 kV/cm electric field strength, and 250 μs total treatment time. The PEF processing caused up to 1 log₁₀ cfu/mL reduction in S. Enteritidis population in LWE. The PEF-treated samples were subjected to heat at 55C for 3.5 min to inactivate the remaining bacteria without denaturing the LWE. The combination of PEF and heat treatments led to a 4.3 log₁₀ cfu/mL reduction in S. Enteritidis population (P < 0.05 ) and caused no significant change in viscosity, electrical conductivity, color, pH, and Brix, relative to control samples (P > 0.05 ). The PEF + 55C treated LWE samples presented significantly longer shelf-life at 4C compared with the control and heat treated samples (P < 0.05 ).     

MAXIMUM CHANGE IN PHYSICAL AND QUALITY PARAMETERS OF FLUID FOODS DURING CONTINUOUS FLOW HEATING. APPLICATION TO LIQUID WHOLE EGG

A fluid in continuous flow heating approaches maximum thermal treatment as the viscosity profile becomes plug flow. This effect is examined for physical and quality changes in tubular heating of fluid foods. Arrhenius mathematical forms of constituent change are incorporated into the thermal profile models for the general case. Application to soluble protein loss (SPL) and viscosity change in liquid whole egg (LWE) are used as examples. Time and temperature schedules are suggested for pasteurization of LWE at elevated temperatures and shorter times, relative to standard schedules, based on the plug flow velocity profile assumption.     

METHODS FOR THE DETERMINATION OF VOLATILE NITROSAMINES IN MALT,WORT AND BEER

Methods for the analysis of beer, wort and malt for NDMA at the one in 10⁹ level using the thermal energy analyzer have been evaluated. The beer and wort procedure using Preptube extraction has been shown to give excellent results. For malt, the preparation of an aqueous extract, followed by analysis by the beer procedure, also gives excellent results. Vacuum distillation from mineral oil has also been examined for the analysis of malt. Providing sufficient aqueous phase is initially present, this procedure yields results similar to those from aqueous extraction. The methods will also detect NDEA, although no NDEA has been observed in any of the beer, wort or malt samples examined. NDMA has been observed to be present in bound forms in malt and Preptubes and is released by the addition of water     

葡萄及葡萄酒中的有机酸及降酸研究

为了探索降低葡萄酒中过量有机酸的有效方法,综述了葡萄和葡萄酒中有机酸的形成及变化,较系统地论述了国内外葡萄酒降酸研究的进展,着重介绍了本研究室以粟酒裂殖酵母与葡萄酒酵母为亲株,采用原生质体融合技术进行生物降酸的研究。