A review of the analytical methods to determine organic acids in grape juices and wines

The determination of low molecular weight organic acids in grape juices and wines is important because of their influence in organoleptic properties (flavour, colour and aroma) and in the stability and microbiologic control of these beverages. The analysis of these acids allows to check the process of maturation of grapes and to control the evolution of the acidity of wines during the several stages of their elaboration process (alcoholic fermentation, malolactic fermentation, aging process, etc).

In this work, a comprehensive review of the analytical methods developed for the determination of short-chain organic acids in grape juices and wines has been shown. This review included non-enzymatic spectrophotometric, enzymatic, chromatographic and electrophoretic methods. Details of the chromatographic and electrophoretic conditions of these methods have been collected in tables.     

UV-C treatment of juices to inactivate microorganisms using Dean vortex technology

A laboratory-scale UV-C treatment device based on Dean vortex technology was tested for its potential to inactivate spoilage microorganisms in cloudy fruit juices. A log 5 and log 6 reduction could be achieved by inactivating Lactobacillus plantarum BFE 5092 and Escherichia coli DH5α in naturally cloudy apple juice at 1.9 and 7.7 kJ/L, respectively. A treatment with 9.6 kJ/L led to an approximately log 4 inactivation of Saccharomyces cerevisiae DSM 70478 and Alicyclobacillus acidoterrestris DSM 2498. The effects of possible influencing parameters such as optical density, turbidity and viscosity were analyzed with regard to the efficiency of the UV-C treatment. The optical density based on dissolved compounds appeared to be the most important factor which influenced the bacterial inactivation efficiency. Cell counts of L. plantarum BFE 5092 could be reduced in quarter-strength Ringer’s solution adjusted with dye from an initial level of approximately 1 × 10⁸-1 × 10¹ cfu/mL at an optical density (254 nm) of 20 at 9.6 kJ/L. Only a log 1.5 reduction, however, could be achieved at an optical density (254 nm) of 140 using the same UV-C treatment. Furthermore, no noticeable effect on inactivation could be determined by varying the turbidity or the viscosity of the juices investigated. An increasing flow rate and the consequently higher Dean number clearly improved the efficacy of the UV-C treatment. Thus, the inactivation of L. plantarum BFE 5092 in blood orange juice could be enhanced by an approximately 2.5-log reduction by increasing the Dean number from 32 to 256 at 7.7 kJ/L. The UV-C treatment using Dean vortex technology was shown in this study to effectively inactivate microorganisms even in cloudy juices. The optical density value seemed to be the exclusive determining factor on the efficiency of the UV-C inactivation of microorganisms based on Dean vortex technology, while the effect of suspended solids was negligible as a result of the efficient mixing by Dean vortices.     

刺葡萄汁与其它几种葡萄汁及葡萄酒的原花青素含量对比

采用铁盐催化比色法,对刺葡萄汁、巨峰葡萄汁以及几种商品葡萄汁和2种葡萄酒中的原花青素含量进行了对比测定。结果表明:刺葡萄汁中的原花青素含量为3147μg/mL,巨峰葡萄汁为1187μg/mL,Welch’s紫葡萄汁2476μg/mL,蒙娜丽莎干红葡萄酒2854μg/mL,长城干红葡萄酒2757μg/mL,可见刺葡萄汁中原花青素含量显著高于其它葡萄汁和葡萄酒中的含量。     

Simple determination of main organic acids in grape juice and wine by using capillary zone electrophoresis with direct UV detection

An accurate, simple and rapid capillary zone electrophoresis (CZE) method with direct UV detection has been set up for the determination of main organic acids in grape juice and wine. The determination of tartaric, malic, and citric acids in grape juices and tartaric, malic, succinic, acetic, lactic and citric acids in wines can be achieved in less than 3 min with only a simple dilution and filtration treatment of the sample. Validation parameters of the method as detection and quantification limits, linearity, precision (intraday and interday analysis) and recovery were also studied in grape juice, white wine, rose wine and red wine, separately. The proposed method decreases the analysis times of the previous reported CZE methods and allows the rapid control of the grape maturity, the winemaking processes and the detection of wine alterations and/or illnesses.     

Ascorbic acid improves the antioxidant activity of European grape juices by improving the juices' ability to inhibit lipid peroxidation of human LDL in vitro

Antioxidant activities of red and white European grape juices towards copper induced lipid oxidation of human low-density lipoproteins (LDL) were examined in vitro . LDL lipid peroxidation was assessed spectrophotometrically by monitoring the development of conjugated lipid hydroperoxides at 234 nm. Red grape juice concentrate inhibited lipid peroxidation of LDL by prolonging the lag phase by 2.7 times relative to a control when evaluated at a total phenolic concentration of 10 μM gallic acid equivalents (GAE). Both red grape juices tested blocked lipid peroxidation of LDL at 20 μM GAE. White grape juice exerted prooxidant activity at 5–20 μM GAE. The antioxidant activity, inhibition of lipid peroxidation of LDL in vitro , was correlated with the juices' levels of total phenols ( r  > 0.98, P  < 0.01), anthocyanins ( r  > 0.99, P  < 0.01), flavan-3-ols ( r  > 0.97, P  < 0.05), and hydroxybenzoates ( r  > 0.96, P  < 0.05) when the phenolic composition of each grape juices was analysed by HPLC. 5 μM ascorbic acid alone did not exert antioxidant activity towards LDL, but combinations of 5 μM ascorbic acid with 5 μM GAE juice phenols eliminated the prooxidant activity of white grape juice, and significantly improved the antioxidant activities of red grape juices.     

Inactivation of natural microorganisms in litchi juice by high-pressure carbon dioxide combined with mild heat and nisin

The individual and combined effects of high-pressure carbon dioxide (HPCD), mild heat (MH) and nisin (200 ppm) on the inactivation of natural microorganisms, including aerobic bacteria (AB), yeasts and molds (Y&;M), in litchi juice were evaluated. The samples were treated at a pressure of 10 MPa and temperatures of 32, 42 or 52 °C for 5, 10, 15, 20, 25 or 30 min. Temperature played a prominent role in the inactivation of both AB and Y&;M when combined with HPCD, particularly for AB at 52 °C and Y&;M at temperatures ≥42 °C. Nisin increased the susceptibility of AB to the combined treatment of HPCD and MH (HPCD + MH). A reduction of 4.19 log cycles was achieved by HPCD + MH at 52 °C for 15 min, and complete inactivation of AB was obtained by combination of HPCD, MH and nisin (HPCD + MH + nisin). No significant effect of nisin was found on the inactivation of Y&;M.     

连续流动-水杨酸盐分光光度法测定葡萄酒及 葡萄汁中氨氮含量

目的利用连续流动分析仪建立以水杨酸-次氯酸盐比色法为基础的葡萄酒和葡萄汁中氨氮的分析方法。方法葡萄汁及葡萄酒样品经过滤后直接进样,试样与试剂在蠕动泵的推动下进入化学反应模块,在密闭的管路中连续流动,并按特定的顺序和比例混合、反应,显色完全后进入流动检测池进行光度检测。结果氨氮标准溶液利用12%乙醇溶液配制线性范围为0~60 mg/L,相关系数(r2)大于0.999;方法检出限(LOD)为0.015mg/L。在低、中、高三个浓度水平添加下,样品氨氮回收率范围为90.0%~96.8%,相对标准偏差(n=6)均小于1%。结论该方法灵敏度高,重复性好,操作简便,适用于大批量葡萄酒和葡萄汁中氨氮含量的检测。     

紫外线技术在纺织印染行业中的应用

简要介绍了紫外线技术在纺织印染行业中的应用,如处理纺纱用胶辊、利用其荧光效应鉴别纤维织物或服装的纤维种类、纤维表面改性以及固化处理等方面.指出紫外线技术是一种环保、高效、简便、快速的处理技术.用紫外线技术处理纺织品不用水作介质,也无需化学品、蒸汽,省去了烘干过程和废水处理,可操作性强,设备投资费用低.由于新型紫外光源的出现,紫外线技术得到了迅速发展.在Et益注重节能、环保的今天,紫外线技术的研究和应用前景将更加广阔.     

Stability of Pycnogenol® as an ingredient in fruit juices subjected to in vitro gastrointestinal digestion

BACKGROUND: The enrichment of fruit juices with concentrated polyphenolic extracts is an expedient strategy to compensate possible phenolic loss through gastrointestinal processing. Pycnogenol®, a standardised procyanidin‐rich extract from pine bark, has been proposed as a potential candidate for polyphenol enrichment of foods. In this study the effects of in vitro digestion on the phenolic profile of fruit juices enriched with Pycnogenol® were investigated. RESULTS: After in vitro digestion the level of detectable total phenolic compounds (expressed as gallic acid equivalent) was higher in both pineapple and red fruit juices enriched with Pycnogenol® than in non‐enriched commercial juices. Five phenolic monomeric compounds were identified by high‐performance liquid chromatography, namely chlorogenic acid, caffeic acid, ferulic acid, gallic acid and taxifolin, the last two being predominant. In vitro digestion of both Pycnogenol®‐enriched pineapple and red fruit juices led to a significant (P < 0.05) increase in detectable chlorogenic and ferulic acids, indicating that hydrolysis of more complex molecules occurs. On the other hand, in vitro digestion of non‐enriched juices was associated with a decrease in gallic and caffeic acids in pineapple juice and with a decrease in ferulic acid in red fruit juice. In no case did in vitro digestion increase the amount of detectable phenolic compounds in non‐enriched juices. CONCLUSION: The stability of Pycnogenol® after in vitro gastrointestinal digestion makes it a good choice for phenolic enrichment of fruit juices. Copyright © 2010 Society of Chemical Industry     

Changes in the polyphenolic and volatile content of “Fino” Sherry wine exposed to high temperature and ultraviolet and visible radiation

Experiments of accelerated oxidation of “Fino” Sherry wines have been conducted at different temperatures (25 and 45 °C) and under the influence of UV–Vis radiation (a xenon lamp of 1500 W). Two types of glass bottle were employed: topaz bottles (with low values of transmittance in the UV–Vis range) and transparent bottles. To identify significant differences between the wine before and after being subjected to the influence of these factors, the values of absorbance at 420 nm and the concentrations of various polyphenolic and volatile compounds were submitted to a multivariate variance analysis. The three factors “temperature”, “radiation”, and “time” had a statistically significant effect on the values of absorbance at 420 nm and on the concentration of most of the polyphenolic and volatile compounds, while the “bottle” factor was only significant for polyphenol content. All the wines showed losses in several polyphenolic compounds, which were more severe for the wines bottled in transparent glass. The combined application of high temperature and UV–Vis radiation provoked significant decreases in most of the volatile compounds monitored.     

Estimation of rumen outflow in dairy cows fed grass silage-based diets by use of reticular sampling as an alternative to sampling from the omasal canal

A study was conducted to compare nutrient flows determined by a reticular sampling technique with those made by sampling digesta from the omasal canal. Six lactating dairy cows fitted with ruminal cannulas were used in a design with a 3 × 2 factorial arrangement of treatments and 4 periods. Treatments were 3 grass silages differing mainly in neutral detergent fiber (NDF) concentrations: 412, 530, or 639 g/kg of dry matter, each combined with 1 of 2 levels of concentrate feed. Digesta was collected from the reticulum and the omasal canal to represent a 24-h feeding cycle. Nutrient flow was calculated using the reconstitution system based on 3 markers (Co, Yb, and indigestible NDF) and using ¹⁵N as a microbial marker. Large and small particles and the fluid phase were recovered from digesta collected at both sampling sites. Bacterial samples from the reticulum and the omasum were separated into liquid- and particle-associated bacteria. Reticular samples were sieved through a 1-mm sieve before isolation of digesta phases and bacteria. Composition of the large particle phase differed mainly in fiber content of the digesta obtained from the 2 sampling sites. Sampling site did not affect marker concentration in any of the phases with which the markers were primarily associated. The ¹⁵N enrichment of bacterial samples did not differ between sampling sites. The reticular and omasal canal sampling techniques gave similar estimates of marker concentrations in reconstituted digesta, estimates of ruminal flow, and ruminal digestibility values for dry matter, organic matter, starch, and N. Sampling site × diet interactions were also not significant. Concentration of NDF was 2.2% higher in reconstituted omasal digesta than in reconstituted reticular digesta. Ruminal NDF digestibility was 2.7% higher when estimated by sampling the reticulum than by sampling the omasal canal. The higher estimate of ruminal NDF digestibility with the reticular sampling technique was due to differences in NDF concentration of reconstituted digesta. This study shows that nutrient and microbial protein outflow from the rumen can be measured using a reticular sampling technique. The reticular sampling technique provides a promising alternative to sampling from the omasal canal because there is less interference with the animal and it does not require advanced sampling equipment.     

南美白对虾产业发展报告

为研究乳酸链球菌素（Nisin）对高水分烤虾常温下贮藏性的影响,在烤虾样品中分别添加20、60和100 mg/kg的Nisin,以感官结合菌落总数、蜡样芽孢杆菌数、挥发性盐基氮、pH等指标对样品品质进行评价。结果表明,烤虾的感官评分在常温贮藏过程中逐渐下降,菌落总数、蜡样芽孢杆菌数、挥发性盐基氮与pH则呈增长趋势。随着Nisin添加量的增加,菌落总数、蜡样芽孢杆菌数、挥发性盐基氮的增长趋慢。第6 d时,未加Nisin的对照组样品菌落总数达到行业标准《调味烤虾》中规定的限值（3×10⁴ CFU/g）,而添加20、60、100 mg/kg Nisin的样品,菌落总数达到规定限值的时间分别被延长至8、12和14 d。本研究表明Nisin对高水分烤虾中蜡样芽孢杆菌等腐败微生物生长有明显的抑制作用,能有效延长产品的货架期。     

Novel implementation of laser ablation tomography as an alternative technique to assess grain quality and internal insect development in stored products

In the last century, there have been important advances in peering inside the internal grain environment. This has included electrical conductance mills, acoustical tools, near-infrared spectroscopy, and soft X-ray imaging. Each technique has their own advantages and limitations. In this current study, we describe a novel process for assessing grain quality and internal insect development in grain using laser ablation tomography (LATscan) and compare it to soft X-ray imaging for three life stages (larva, pupa, adult) of Sitophilus zeamais and Rhyzopertha dominica. Our results suggest that X-rays overestimated grain volume loss by about a quarter compared to LATscan. Moreover, LATscan produces a rich digital dataset on the level of microns that can be explored to ask biologically-relevant questions. We discuss the current limitations of LATscan in context with other techniques. Ultimately, the results highlight LATscan as a useful additional tool to further our understanding pest-commodity interactions in the postharvest supply chain.     

基于喀什地区职业院校设置服装设计与工艺专业的必要性探究--以喀什职业技术学院为例

新疆发展纺织服装产业是带动百万人就业的重大决策。目标是到2020年,新疆纺织服装产业就业容量达60万人,喀什地区达6万人;预计到2023年,新疆服装企业就业容量达50万人,喀什纺织服装企业就业容量10万人,其中服装需求为5万人。通过调研,喀什地区纺织服装企业89%生产服装服饰用品。增设高职服装设计与工艺专业,可以满足本地高中生、服装中专毕业生学历提升的需求和企业用人的需求。对贫困家庭学子而言,因高职薪资普遍高于中职,一人就业能使全家脱贫,对维护喀什地区社会稳定以及脱贫攻坚具有重要的作用。     

Determination of total phenols in tea infusions,tomato and apple juice by terbium sensitized fluorescence method as an alternative approach to the Folin–Ciocalteu spectrophotometric method

A fast screening of total phenols in tea infusions, tomato and apple juice samples using terbium sensitized fluorescence is described. The proposed method is based on the fluorescence sensitization of terbium (Tb³⁺) by complexation with flavonols (quercein as a reference standard) (at pH 7.0), which fluoresces intensely with an emission maximum at 545 nm when excited at 310 nm. Quercetin and terbium cations (at pH 7.0) form a stable complex and the resulted emission at 545 nm can be used for the determination of the total phenols concentration expressed in terms of “quercetin equivalent”. Based on the obtained results, a sensitive, simple and rapid spectrofluorimetric method was developed for the determination of total phenols. In the optimum conditions, the calibration graph was linear from 0.01 to 2 μg mL⁻¹, with the limit of detection of 0.002 μg mL⁻¹. The relative standard deviation values were in the range of 0.75–2.3%. The total concentrations of quercetin equivalent in five tested samples were found in the range of 6.6–27.9 μg mL⁻¹ and the results compare favorably with those obtained by spectrophotometric method (r = 0.999).