ORGANIC ACIDS PROFILE IN TOMATO JUICE BY HPLC WITH UV DETECTION

A simple method was developed to determine 10 organic acids simultaneously in tomato products using reverse‐phase high performance liquid chromatography (HPLC) column with the diode array detector set at 210 nm. After centrifugation and filtration, the samples were passed through to an anion exchange resin and the organic acids were released using 0.1 N HCl. The chromatographic separation was achieved with isocratic analysis in a 20‐min run. The method was reliable and sensitive. The coefficient of determination of the standard calibration curve is 0.9925 ≤ r² ≤ 0.9999 and the limit of detection ranged from 0.08 to 6.00 mg/kg for trans‐aconitic acid and acetic acid, respectively. The limit of quantification ranged from 0.19 to 15.18 mg/kg for trans‐aconitic and acetic acid, respectively. To establish the efficiency of the anion resin the procedure was applied to a standard solution of a mixture of organic acids. The organic acids recovery ranged from 87.0% ± 1.9 for citramalic acid to 109.9% ± 5.2 for fumaric acid.     

RELATIONSHIPS OF COLOR, VISCOSITY, ORGANIC ACID PROFILES AND ASCORBIC ACID CONTENT TO ADDITION OF ORGANIC ACIDS AND SALT IN TOMATO JUICE

Malate and citrate acidified juices produced statistically similar results for pH and titratable acidity (TA), but these acidified juices were significantly different from nonacidified juice when comparing pH and TA. During storage time, the pattern of the pH and TA curves, regardless of acidification, were similar. Salted juice exhibited a significantly higher ascorbic acid content and greater viscosity than did the unsalted juice during storage. The organic acids citric, lactic, malic, and pyrocarboxylic increased immediately after heat processing for commercial sterility, while the presence of salt in this juice lowered these same organic acids. There was minimal correlation of the organic acids or the summation of the acids equivalents of all the organic acids to the titratable acidity or pH of the juices. Juices acidified with malate or citrate did not consistently display an increased level of that specific acid after processing and storage.     

VISCOSITY AS AFFECTED BY VARIOUS CONSTITUENTS OF TOMATO JUICE

SUMMARY— Degradation of proteins of tomato juice with pronase caused a relatively small loss of viscosity. Commercial cellulase freed of pectolytic activity with 8 M urea greatly decreased the viscosity of washed tomato solids. Further degradation with pectinase was ineffective in reducing viscosity. Cellulase extracted from the tomato lowered viscosity of tomato juice. Enzymatic degradation as indicated by chemical analysis did not always result in a loss of viscosity. By extracting the solids with water, viscosity of tomato juice was lowered drastically. The extent of the reduction was not affected by previous treatment with cellulase or pectinase. Viscosity was not affected by extraction with versene. The greater reduction in viscosity of tomato juice by extraction of the solids with water than with ethanol indicates that the high molecular polymers associated with the insoluble solids contribute greatly to viscosity. The data did not indicate a significant contribution of the uronides to the viscosity of tomato juice.     

NONVOLATILE ORGANIC ACIDS IN GUAVA

ABSTRACT— The nonvolatile organic acids of guava were extracted and isolated. TLC of the acids showed the presence of 6 acids, 5 of the acids identified as lactic, malic, citric, ascorbic and galacturonic. GLC of the methyl esters of the guava acids confirmed the presence of malic, citric and lactic acid. Quantitative determinations using succinic acid as an internal standard showed citric and malic acid to be present in almost equal amounts and lactic acid in much lesser amount in cultivated guavas. In wild guavas, citric acid was the predominant acid, with lesser amounts of malic and lactic acids.     

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。     

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.     

VISCOSITY AND QUALITY OF TOMATO JUICE AS AFFECTED BY PROCESSING METHODS

ABSTRACT

Quality and viscosity of tomato juice is strongly governed by mechanical and thermal abuse during processing. The effect of processing and storage duration on the viscosity and quality parameters of tomato juice was evaluated in the present work. Tomato juice was obtained by two different methods, normal method (NM) and variable method (VM), and was heated by both conventional and microwave hot break treatments. Tomato juice was evaluated for various quality characteristics including precipitate weight ratio, degree of serum separation (DOSS), Brookfield viscosity, lycopene levels, vitamin C, phenols and antioxidant activity. Changes observed in several quality parameters during storage were statistically insignificant. The methods and processing had the greatest contribution toward viscosity, whereas storage duration had no significant effects. Viscosity parameters viz precipitate weight, DOSS and Bostwick consistency revealed that juice processed by VM was more viscous than that of NM, irrespective of the hot break processing used. Ascorbic acid and lycopene content varied significantly with mechanical methods and processing conditions. However, phenolic content and antioxidant activity remained stable. The variable process represents an improvement over the conventional by enabling tomato processors to improve the consistency of the tomato product.

PRACTICAL APPLICATIONS

Quartering or slicing tomatoes followed by hot break processing techniques can significantly improve the quality of tomato juice in terms of reduced degree of serum separation and precipitate weight ratio. The modified technology could be considered as a viable and economical method for small‐ and medium‐scale tomato processors with limited resources and facilities at their disposal.

     

CHANGES IN THE PROFILE OF ORGANIC ACIDS IN PLAIN SET AND STIRRED YOGURTS DURING MANUFACTURE AND REFRIGERATED STORAGE1

The organic acids profile in fermented dairy foods is an indicator of the metabolic activity of added bacterial cultures. These acids act as natural preservatives and contribute to the characteristic sensory properties. This study was done to determine the effect of encapsulation on the metabolic activity of probiotic supplements, i.e. bifidobacteria, in plain yogurts. Metabolically active bifidobacteria may increase the concentration of certain organic acids, mainly acetic and propionic acids, which might lead to decreased acceptability of the product. Changes in the profiles of organic acids were determined in plain set and stirred‐type yogurts containing the starter culture and microencapsulated and nonencapsulated probiotic strains of either Bifidobacterium longumB6 or B. longum ATCC15708. Ion‐exchange high‐performance liquid chromatography was used for the separation and quantification of the organic acids. Concentrations of acetic and lactic acid increased during storage, while those of citric and uric acid remained stable. No particular pattern was observed for propionic or butyric acid, while pyruvic acid initially decreased and then increased during storage.     

高效液相色谱法测定野蔷薇果中Vc含量的研究

建立一种高效液相色谱法测定野蔷薇中Vc含量的新方法.采用Diamonsil 5μ C18反相柱(200mm×4.6mm×5μm)分离;流动相为甲醇-0.01%磷酸水溶液(3:7,体积分数);柱温25℃;流速1.0mL/min;二级管陈列检测器,检测波长254nm.Vc在浓度为20mg/L～1500mg/L范围内呈良好的线性关系,线性回归方程为y=17.136x 120.8,相关系数为0.9992,方法回收率为97%～101%相对标准偏差小于3%.该方法简便、快速、准确、适合于测定其它水果和蔬菜中Vc的含量.     

GAS CHROMATOGRAPHIC DETECTION OF DIACETYL IN ORANGE JUICE

A GLC method was developed for detection of diacetyl (2,3-butanedione) and acetoin (3-hydroxy-2-butanone) in orange juice. Retention times for diacetyl and acetoin were 2.8 ± 0.03 and 6.8 ± 0.02 min, respectively. Concentration by distillation was essential to detect small quantities by GLC of diacetyl but was ineffective for acetoin. A linear response of diacetyl concentration to peak area was observed between 0.05 and 0.5 ppm. The peak areas at 0.05 and 0.5 ppm diacetyl were 1242 ± 203 and 20142 ± 1120, respectively. Elevating the column temperature and decreasing the carrier gas flow rate, increased the limit of detection for acetoin from ≥ 100 ppm to ≥ 10 ppm, but diminished the resolution of the diacetyl peak from juice volatiles.     

转基因番茄DNA检测芯片的研究

自19世纪70年代世界上第一例转基因植物问世以来，它对人类健康及环境的安全性问题，受到了全世界广泛的关注：本研究根据转基因番茄（Zeneea）中所转入的外源基因，选择CaMV35S启动子、NOS终止子、PG／NOS基因和内源PG基因设计特异性引物，采用多重PCR法对待测样品进行扩增，通过缺口平移法合成DIG—dUTP标记杂交探针，并制备基因芯片。在对PCR反应和扩增产物与芯片杂交条件进行优化的同时，比较了芯片检测的特异性和重复性，并对检测的灵敏度进行测试。结果表明，该方法具有较好的特异性和重复性，检测灵敏度可达0．5％，由于采用了多重PCR技术一次可同时检测多个基因，提高了检测的；隹确性和效率。     

THE ROLE of PULP INTERPARTICLE INTERACTION IN DETERMINING TOMATO JUICE VISCOSITY

Pulp interparticle interaction plays a major role in determining the viscosity of tomato juice. Indices of second order and of compounded high order interparticle interaction have been evaluated by diluting tomato juice samples with their own serum, and determining the slope of the reduced viscosity curves at the very dilute and at the original concentration regions, respectively. the second order interaction index, reflecting the behavior of a pair of colliding particles, has practically a similar value for samples having the same process history. On the other hand, tomato juice samples differ markedly in their value of the interaction index describing the effect of high order interparticle interaction on the viscosity at the original juice concentration. the higher that value, the higher the viscosity. the value of this index decreases by concentrating the tomato juice and increases by homogenization. It has a maximum value at pH 4–4.5 and most importantly it is greatly dependent on the mechanical abuse history of the juice. Enzymatic depolymerization of the soluble and especially the insoluble pectin markedly reduces the value of the interaction index, indicating that pectin plays a major role in determining the level of that interparticle interaction.