Chemical Constitution and Antimicrobial Activity of Kefir Fermented Beverage

Kefir beverage (KB) is a fermented milk initiated by kefir grains rich with starter probiotics. The KB produced in this study seemed to contain many chemical compounds elucidated by gas chromatography–mass spectrometry (GC-MS) and IR spectra. These compounds could be classified into different chemical groups such as alcohols, phenols, esters, fatty esters, unsaturated fatty esters, steroids, polyalkenes, heterocyclic compounds and aromatic aldehydes. Both KB and neutralized kefir beverage (NKB) inhibited some pathogenic bacteria including Escherichia coli ATCC11229 (E. coli), Listeria monocytogenes ATCC 4957 (L. monocytogenes), Bacillus cereus ATCC 14579 (B. cereus), Salmonella typhimurium ATCC 14028 (Sal. typhimurium) as well as some tested fungal strains such as Aspergillus flavus ATCC 16872 (A. flavus) and Aspergillus niger ATCC 20611 (A. niger), but the inhibitory activity of KB was more powerful than that obtained by NKB. It also appeared to contain four lactic acid bacteria species, one acetic acid bacterium and two yeast species. Finally, the KB inhibited distinctively both S. aureus and Sal. typhimurium bacteria in a brain heart infusion broth and in some Egyptian fruit juices, including those made with apples, guava, strawberries and tomatoes.     

氧化铱纳米颗粒修饰碳纤维电极用于水果中pH在线检测

pH检测在农业生产、食品加工、环境保护、疾病诊断等领域有着重要意义.电化学法具有响应速度快、灵敏度高和操作简单等优点,是目前最常用的pH检测方法之一.然而,商品化的pH计存在体积大、质子敏感膜易损等问题,仅能在相对稳定的样本溶液环境中工作,并不适用于植入式pH分析.本文将氧化铱纳米颗粒修饰在碳纤维微电极表面,构建了一种微型、可植入的固态pH传感器.该传感器具有超能斯特pH响应,可以达到约65.5 mV/pH的灵敏度,宽检测范围(pH≈2–12)和较高稳定性.最后我们将该pH传感器植入水果组织内,实现了水果内pH值的在线检测.     

Analysis of native carotenoid composition in orange juice using C30 columns in tandem

In the present contribution, a novel analytical approach based on using serial coupled conventional LC columns is proposed to the study of the native carotenoid composition of orange juice. The great difficulties that are found when analyzing complex carotenoid samples, due to the high natural variability of these compounds as well as to the presence of carotenoid esters are well documented. To overcome some of these limitations, we have developed a methodology including the study of both the saponified and the intact sample by means of two different LC-DAD/APCI-MS methods. The increase in the resolution and separation power obtained when using two serial coupled C(30) columns is demonstrated, and significant increases in peak capacity have been achieved. By using this new methodology, 44 different carotenoids have been tentatively identified. Among them, several violaxanthin diesters have been directly identified in orange juice for the first time. The main carotenoids in orange juice were violaxanthin, lutein, luteoxanthin, 9-cis-antheraxanthin, and beta-cryptoxanthin. Some of them were found in both their free and esterified forms. To the best of our knowledge, this is the first application of serial couplings of C(30) columns for the identification of the native carotenoid composition of natural matrices.     

Multicomponent pervaporation process for volatile aroma compounds recovery from pomegranate juice

The present work describes the possibility of using pervaporation process to recover the pomegranate aroma compounds from an actual pomegranate juice and a model aroma solution. Four different chemicals representing four major kinds of aroma compounds, namely, 3-methyl butanal, isopentyl acetate, n-hexanol and α-ionone, were utilized in this work. Three POMS membranes and two PDMS membranes were tested for pervaporation and compared for their separation performance. The influence of various operating parameters such as feed flow rate, feed temperature and permeate pressure on the permeation flux and aroma compounds enrichment factor was investigated. Feed flow rate was shown to have no significant effect on both total flux and aroma enrichment factor, whereas feed temperature and permeate pressure had highly significant effects. An increase in feed temperature led to higher flux and enrichment factor. As permeate pressure increased, the flux and enrichment factor of some aroma compounds decreased. Some of the aroma compounds showed higher enrichment factor at higher permeate pressures. Finally, the activation energy of permeation and the membrane permeability for each aroma compound were determined.     

Comparison of different extraction methods for the simultaneous determination of pesticide residues in kiwi fruit using gas chromatography-mass spectrometry

The methods of simultaneous extraction of iprodione, chlorpyrifos-methyl, EPN and endosulfan (with its metabolites) from kiwi fruit using accelerated solvent extraction (ASE), supercritical fluid extraction (SFE), and liquid-liquid extraction (LLE) were tested and compared in terms of their of limits of detection and quantification, as well as the highest pesticide recoveries with the lowest residues in the final extracts. The analysis was performed using gas chromatography-mass spectrometry in the selected ion monitoring mode. The proposed methods featured good sensitivity, pesticide quantification limits were low enough, and the precision (expressed as relative standard deviations) ranged from 0.56 to 7.17%. The recoveries obtained from ASE, SFE and LLE were 77.5-120, 71.9-109.1 and 75.6-127.1%, respectively. The proposed methods were successfully applied for the monitoring of the selected pesticide residues in kiwi fruit samples collected from Jollanamdo area, Republic of Korea. Iprodione was detected at a level lower than the maximum residue limit (MRL) established by the Korea Food and Drug Administration (5 ppm), while EPN was detected at a level higher than the Korea Food and Drug Administration MRL (0.1 ppm) in the real samples. The proposed sample preparations led to a higher preconcentration of the pesticide fraction, and allowed the sensitive and selective determination of pesticides with varied physicochemical properties in kiwi fruit. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Evaluation of Cashew Apple Juice for the Production of Fuel Ethanol

A commercial strain of Saccharomyces cerevisiae was used for the production of ethanol by fermentation of cashew apple juice. Growth kinetics and ethanol productivity were calculated for batch fermentation with different initial sugar (glucose + fructose) concentrations. Maximal ethanol, cell, and glycerol concentrations were obtained when 103.1 g L⁻¹ of initial sugar concentration was used. Cell yield (Y _X/S) was calculated as 0.24 (g microorganism)/(g glucose + fructose) using cashew apple juice medium with 41.3 g L⁻¹ of initial sugar concentration. Glucose was exhausted first, followed by fructose. Furthermore, the initial concentration of sugars did not influence ethanol selectivity. These results indicate that cashew apple juice is a suitable substrate for yeast growth and ethanol production.     

微柱高效液相色谱法分离八角茴香挥发油成分

利用微柱高效液相色谱法(μ-HPLC)对八角茴香果实挥发油成分进行了分离,对固定相类型、流动相组成及流速等条件进行了优化。结果表明,选用氰基分析柱(250mm×0.32mmi.d.,5μm),正己烷-乙腈-二氯甲烷(80∶8∶12,体积比)为流动相,流速为2μL·min-1,八角茴香果实挥发油成分在微柱液相色谱上分离效果最好。在优化的实验条件下,对实际样品中反式-茴香醚、茴香醛等成分进行了定量。本实验为以后的μ-HPLC与毛细管气相色谱联用分析植物挥发油奠定了基础。     

A covalently cross‐linked microporous polymer based micro‐solid phase extraction for online analysis of trace pesticide residues in citrus fruits

Covalently cross‐linked microporous polymers are a new class of highly cross‐linked porous network materials with large surface area and potential superiority in sample pretreatment. In this work, a covalently cross‐linked microporous polymer was well designed and synthesized by condensation of acylhydrazines in terephthalic dihydrazide with aldehyde groups in 1,3,5‐benzenetricarboxaldehyde. The adsorption mechanism was explored and discussed based on π‐π stacking interaction and steric effect. Then, a covalently cross‐linked microporous polymer was employed as the adsorbent of online micro‐solid‐phase extraction coupled with high‐performance liquid chromatography for the enrichment and analysis of trace pesticide residues in citrus fruits. The method was successfully applied to the online analysis of sugar orange and Huangdigan samples with the detection limits of 0.10–0.30 μg/kg. It was satisfactory that chlorpifos and triazophos in real sugar orange and Huangdigan samples could be actually found and quantified at concentrations of 0.20 and 0.51 mg/kg, respectively. The recoveries of sugar orange and Huangdigan samples were in the range of 70.0–103 and 74.0–119% with relative standard deviations of 0.4–9.7 and 0.5–9.2% (n = 3), respectively. The proposed method was accurate, reliable, and convenient for the online simultaneous analysis of trace pesticide residues in citrus fruits.     

Turbo flow在线净化-超高效液相色谱-串联质谱法检测水果中5种咪唑类农药残留

建立了Turbo flow （TF）在线净化-超高效液相色谱-串联质谱同时检测水果中吡咪唑、咪唑烟酸、咪鲜胺、咪唑嗪和咪唑菌酮等5种咪唑类农药的方法。以饱和氯化钠溶液溶解样品,乙腈提取,蒸干,乙腈-水（1：1,v/v）溶液定容后进入Turbo flow-超高效液相色谱-串联质谱系统分析,外标法定量。对影响TF净化的条件如TF色谱柱、流动相、洗脱溶液、洗脱速率等进行了优化。在优化的实验条件下,以Turbo flow C18 （50 mm×1.0 mm）为净化柱,Hypersil GOLD aQ （100 mm×2.1 mm）为分析柱,乙腈和5 mmol/L甲酸铵溶液（含0.1%（v/v）甲酸）为流动相进行梯度洗脱,在电喷雾正离子选择反应监测模式下进行检测。结果表明,各目标化合物在0.0075~0.75 mg/L范围内线性关系良好（相关系数均大于0.99）,定量限为0.005 mg/kg。对实际样品分别加标0.005、0.01、0.05和0.5 mg/kg,回收率为71.2%~122.4%,相对标准偏差（RSD）为0.5%~8.9%。该方法简便、快速,结果准确可靠,适用于水果中5种咪唑类农药残留的检测。     

超高效液相色谱-串联四极杆质谱法测定葡萄中单咖啡酰酒石酸酯、单香豆酰酒石酸酯和单阿魏酰酒石酸酯

建立了超高效液相色谱-串联四极杆质谱测定葡萄汁、皮和籽中羟基桂皮酒石酰酯类化合物含量的方法。采用的色谱柱为Waters UPLC HSS T3 (150 mm×2.1 mm, 1.7 μm),流动相为含0.1%甲酸的水-乙腈体系,梯度洗脱,流速0.3 mL/min,柱温35 ℃;质谱采用电喷雾离子源、负离子多反应检测模式。对单香豆酰酒石酸酯和单阿魏酰酒石酸酯,其含量以单咖啡酰酒石酸酯当量表示。结果表明,单咖啡酰酒石酸酯在25～2000 μg/L范围内线性关系良好(r2=0.9989);检出限为0.25 μg/L,定量限为25 μg/L;在250、750、1200 μg/L添加水平下单咖啡酰酒石酸酯的平均回收率为97.7%～99.5%,相对标准偏差小于2.5%。实验结果表明,葡萄汁、皮和籽中羟基桂皮酒石酰酯类化合物的含量差异显著。该方法简单快速、灵敏度高、回收率高、准确性好,可用于葡萄产品中单咖啡酰酒石酸酯、单香豆酰酒石酸酯和单阿魏酰酒石酸酯的分析。