Metrological concepts required for food safety and quality testing

The safety of the food we consume has a direct impact on our well-being and is a determinant for the quality of life. Food testing and the metrological principles associated with this activity play a key role in helping to ensure the safety of the food chain. The globalisation of food trade and national as well as international food safety regulations has produced an enormous demand for comparability of analytical results independent of temporal or spatial borders. Measurement-related elements of EU food legislation and their practical implementation as well as analytical requirements derived from the Codex Alimentarius are discussed in this contribution.     

成像技术在食品安全与质量控制中的研究进展

食品质量与安全是政府、食品行业以及消费者十分关注的问题。为了保证食品质量与安全,需要对食品中的风险因子进行检测。传统的分析方法如生物化学方法和仪器分析方法(色谱法、色谱-质谱法)存在前处理比较复杂,耗时,对样品具有破坏性及无法获取目标物空间信息等缺点。因此,开发快速,无损,实时和可视化的检测技术十分重要,这也是食品领域研究的热点。近年来,高光谱成像技术融合了成像和光谱两种技术,可以作为一种用于食品质量和安全评估的非破坏性和实时检测的工具。拉曼光谱成像技术可以同时获得待测物的光谱和空间信息,具有快速,无损和低成本等优点,在食品安全评价和质量控制中也得到了成功应用。质谱成像技术不需要标记和染色,即可实现样品组织表面待测物的可视化和高通量分析。它作为一种分子可视化技术,可以获得食品中营养成分及内、外源性有害物质的空间分布信息,在食品领域也表现出良好的应用前景。本文检索了近几年国内外发表的成像技术在食品研究中的相关文献,介绍了高光谱成像技术、拉曼光谱成像技术和质谱成像技术的原理,并综述了它们在食品安全与质量控制中的应用。此外,本文分析和讨论了这几种成像技术的优缺点,并对成像技术在食品领域的发展...     

Mass spectrometric analysis for carboxylic acids as viable markers of petroleum hydrocarbon biodegradation

The characterization of metabolites, which are considered markers of bacterial degradation of hydrocarbons, is gaining in importance. Over the years, carboxylic acids have served as useful indicators of aerobic and anaerobic hydrocarbon biodegradation. This interest has been accompanied by the extensive and robust development of analytical methods for monitoring, untargeted identification, and specific and sensitive determination of carboxylic acids in complex matrices. This review discusses critically the state-of-the-art of mass spectrometry as a reliable analytical technique to identify and quantify carboxylic acid metabolites. Attention is paid to sample pre-treatment, selective group pre-concentration, and gas and liquid chromatography preceding mass spectrometry to alleviate matrix effects and ionization discrimination. Recent specific applications of mass spectrometry in monitoring carboxylic acids for assessing hydrocarbon biodegradation are reviewed. Presently, no single technique is sufficient for holistic profiling of carboxylic acids. The direct characterization of carboxylic acids by mass spectrometry is the ultimate goal but despite recent significant developments, challenges persist.     

Dicarboxylic acids and hydroxy fatty acids in different species of fungi

Secondary metabolites of fungi can be responsible for allergies; therefore, the identification of compounds produced by these organisms is very important. Fungi produce large amounts of secondary metabolites, which belong to groups of chemicals such as: dicarboxylic acids, hydroxy acids, alcohols, hydrocarbons, esters, fatty acids, sterols, amino acids and mycotoxins. The presence of all these compounds in human proximity contributes to many diseases. Therefore, the aim of the study was a qualitative and quantitative analysis of hydroxy and dicarboxylic acids produced by fungi occurring in student hostel in Poland, in the province of Pomerania. The following species of fungi were subjected to extraction: Aspergillus niger, Aspergillus fumigatus, Aspergillus candidus, Rhizopus sp., Geotrichum candidum, and Penicillium chrysogenum. A mixture of ethyl acetate and methanol was used for the extraction. The obtained extracts were further analyzed by gas chromatography mass spectrometry (GC–MS). In all samples of fungi, the presence of a total of 22 acids, including 13 dicarboxylic and 9 hydroxy acids, was confirmed. Most acids (17 different acids) were identified in A. fumigatus. Only 10 acids were identified in the mycelium of G. candidum and A. niger. Acids which were identified in all samples of the mycelium were 22-hydroxydocosanoic acid, 24-hydroxytetracosanoic acid and adipic acid. The most abundant compounds were 22-hydroxydocosanoic acid in A. fumigatus, A. candidus, Rhizopus sp., G. candidum and P. chrysogenum, and succinic acid in A. niger. More experiments are needed to understand the physiological role of hydroxy and dicarboxylic acids. We hope that our results are an important contribution to further studies on the human health.     

Thermal analysis and food quality

Summary Thermogravimetry (TG) and derivative thermogravimetry (DTG) are proposed as a fast and sensitive tool to discriminate the industrial processing of spaghetti pasta by focusing the attention on the thermal profiles of the structured water release. Thirteen different name-brand and store-brand kinds of spaghetti pasta were analysed. The results show different profiles according to the drying procedures. By on-line coupling a FTIR spectrometer to the thermobalance, the evolved gas analysis (EGA) allowed to confirm the water releasing step.     

Histamine-modified cationic beta-cyclodextrins as chiral selectors for the enantiomeric separation of hydroxy acids and carboxylic acids by capillary electrophoresis.

The enantiomeric separation of alpha-hydroxy acids and carboxylic acids was successfully performed by using 6-deoxy-6-N-histamino-beta-cyclodextrin (CD-hm), a monosubstituted positively charged beta-cyclodextrin (beta-CD) bearing a histamine moiety linked to the C6 of a glucose unit in the upper CD rim via the amino group. Good results were obtained at a low selector concentration (1 mM). The number of positive charges on the upper rim may be modulated as a function of pH, because of the different pKa of the amino and the imidazolyl groups, and was found to affect both the enantioselectivity and resolution factors. With the analogous 6-deoxy-[4-(2-aminoethyl)imidazolyl]-beta-cyclodextrin (CD-mh) bearing the histamine moiety linked to the C6 via the imidazolyl group, very poor results were obtained, showing that the proximity of the positive charge to the cavity plays an important role in the enantiomeric recognition. The complexation mode was studied by electrospray ionization-mass spectrometry (ESI-MS) and two-dimensional nuclear magnetic resonance (2-D NMR) ROESY experiments: the recognition model is consistent with an inclusion complexation of the aromatic ring of the analyte within the CD cavity coupled to electrostatic interactions between the carboxylate and the protonated amino group of the cyclodextrin.     

Research in the field of heterocyclic chemistry. XL. Organic acids as intramolecular condensing agents for arylamide hydroxy acids

It is shown that the basic properties of arylamides of diarylglycolic acids are determined not only by the nature of the aryl radicals of the acid part of the molecule, but also by the extent to which hydrogen atoms of the amino groups are substituted. Formation of carbonium salts of arylamides is considerably influenced by the nature of the solvent. Intramolecular condensation of tertiary arylamides of 4, 4-dimethoxy- and 4, 4-dimethylbenzylic acids gives a number of new 1-alkyl (aryl)-3, 3-diaryloxindoles. Ethyl N-n-propyl- and N-isobutyloxanilate and N,N-diethylamide-4, 4-dimethoxybenzylate are described for the first time.For part XXXIX see [1].     

Liquid chromatography-mass spectrometry of hydroxy and non-hydroxy fatty acids as amide derivatives.

A useful method for analyzing fatty acids by liquid chromatography-mass spectrometry with an atmospheric-pressure chemical-ionization interface system has been developed. The sensitivity of six kinds of palmitamide derivatives monitored by a single ion of [M+H]+ was, in decreasing order: N-n-propylamide greater than anilide greater than N,N-diethylamide, amide greater than N,N-diphenylamide greater than N-1-naphthylamide. Individual fatty acids were identified from a mixture of amide derivatives of authentic fatty acids from C16:0 to C30:0 on a mass chromatogram. This method was used to detect both hydroxy and non-hydroxy fatty acids. Many kinds of fatty acid, including hydroxy fatty acids of the rat brain, were detected in a single run.     

Automated clean-up procedure for the analysis of sugars and acids in food

Summary In the gas-chromatographic analysis of sugars and acids in foodstuffs, isolation and purification of the two types of components is time-consuming and laborious. An automated clean-up procedure, based on ion-exchange, has therefore been developed. A liquid food sample is successively percolated over a cation and anion and a cation exchanger. Sugars and acids are collected under the second and third column, respectively. A time programmer operates a set of pumps and a pneumatic valve system enabling simultaneous regeneration of columns not being eluted. Hence, handling of samples is continuous; each clean-up cycle takes 50 min.

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Automatisiertes Abtrennungsverfahren für die Analyse von Zuckern und Säuren in Nahrungsmitteln

Zusammenfassung Eine flüssige Nahrungsmittelprobe wird nacheinander über einen Kationen-, einen Anionen- und einen Kationenaustauscher perkoliert. Die Zucker und die Säuren werden abgetrennt und im Eluat der zweiten bzw. dritten Austauschersäule gefunden. Ein Steuergerät schaltet auf Zeitbasis eine Gruppe von Pumpen und ein System mit pneumatischen Hähnen derart, daß in einem Cyclus (50 min) die Substanzen eluiert und die Säulen regeneriert werden. Anschließend werden die Proben verarbeitet. Einige Ergebnisse verschiedener Nahrungsmittel werden angeführt.

On leave from Lisbon University, Portugal.     

Esterification of aliphatic hydroxy acids to n-propyl esters in aqueous solutions for their gas chromatographic analysis

Summary Aliphatic hydroxy acids were esterified in aqueous solution in the presence of different amounts of sulfuric acid. Esterification of lactic, tartronic, malic and citric acids in water/n-propanol mixtures with mole ratios between 0.03 and 2.15 can be utilized for the determination of these acids by gas chromatography. Water does not interfere at water/n-propanol mole ratios below 0.03. For mole ratios above 0.03 anhydrous sodium sulfate is used for the binding of water. The mole ratio range was 0.24–2.13 for anhydrous sodium sulfate/water, and 0.16–1.28 for sulfuric acid/anhydrous sodium sulfate.     

Esterification of aliphatic hydroxy acids to n-butyl esters in aqueous solutions for their gas chromatographic analysis

Summary Aliphatic hydroxy acids were esterified in aqueous solution in the presence of sulfuric acid. Esterification of lactic, tartronic malic and citric acids in water/n-butanol mixtures with mole ratios between 0.02 and 2.53 can be utilized for the determination of these aliphatic hydroxy acids by gas chromatography. Water does not interfere at water/n-butanol mole ratios below 0.02. For mole ratios above 0.02 anhydrous sodium sulfate is used for the binding of water. The mole ratio range was 0.25–2.53 for anhydrous sodium sulfate/water, and 0.32–1.27 for sulfuric acid/anhydrous sodium sulfate.     

Mass spectrometry of hydroxy dicarboxylic acids as trimethylsilyl derivatives. Rearrangement fragmentations

Gas chromatography—mass spectrometry offers a convenient method for the separation and identification of hydroxy dicarboxylic acids as open-chain trimethylsilyl (TMS) derivatives. Mass spectra were studied of aldaric (tartronic, tartaric, pentaric and hexaric) acids and deoxyaldaric (malic, 2-deoxypentaric, 2-deoxyhexaric, 3-deoxypentaric and 3-deoxyhexaric) acids. The different structural types can be readily identified from their characteristic spectra. The most prominent fragmentations involving the rupture of one bond are the loss of a siliconlinked methyl group and the formation of α-cleavage ions by carbon chain cleavage. The further decay is characterized by a number of significant rearrangements specific of TMS derivatives. Several of these can be classified as involving migration of a TMS group to an oxygen atom or migration of an ester OTMS group to a silicon atom. Concomitant loss of a stable molecule often provides a driving force. Prominent odd-electron ions are formed by a McLafferty-type rearrangement of a TMS group. The decomposition of several even-electron ions can be regarded as analogous to that rearrangement.     

食品中反式脂肪酸分析方法的研究进展

食品中反式脂肪酸(TFAs)对人体健康有重要影响,因此日益受到人们的关注。针对TFAs的分析方法较多,包括光谱分析、色谱分析、质谱分析和电泳分析等。本文就目前报道的TFAs检测方法进行了综述,并详细介绍了各种方法的优缺点及其在相关食品分析中的应用。     

Anion-exchange separation of hydroxy acids in acetate medium

A great number of hydroxy acids have been separated in an anion-exchange column using sodium acetate as eluant. It is essential that lactones be saponified before loading the column. With hydroxy acids containing only one or two hydroxyl groups this method is superior to separations in borate medium. With complicated mixtures the methods supplement each other.     

Thermal analysis and safety in relation to food processing

The adaptation of thermal analysis techniques to study exothermic phenomena and self-ignition of foodstuffs, and the use of special tools to simulate and analyze dust explosions are described. The examples shown should provide a better understanding of the mechanisms involved in phenomena which can lead to the bursting of an autoclave, to fires or to dust explosions during food processing operations.     

GC-MS analysis of hydroxy and epoxy acids from seed oil of Hippopha? rhamnoides

By the GC-MS method using a packed column, in the mixture of TMS derivatives of hydroxy acid methyl esters obtained from the seed oil of the sea buckthorn, in ten chromatographic peaks (CPs) 13 monohydroxy compounds have been characterized by their mass spectra, the main ones being derivatives of dimorphecolic and coriolic acids. Structures are proposed for four dihydroxy acids of the C₁₇–C₂₀ series. The mixture of methyl esters of di- and tetra-TMS derivatives obtained from the mixture of epoxy acids from the same source has been analyzed by a similar method. In seven CPs, 11 compounds, reflecting the presence of nine epoxy acids in the initial mixture, have been characterized by their mass spectra. The main component of the mixture was 15,16-epoxyoctadeca-9,12-dienoic acid.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 626–634, September–October, 1989.     

原位电离质谱技术在食品质量安全检测中的应用

原位电离质谱技术能够在常压环境下直接分析各种食品样品,无需或仅需极少的食品制备,大大提高了分析效率,已经成为一种重要的食品快速分析方法。本文对原位电离质谱的离子化技术和工作流程进行了介绍,从食品污染物检测、非法添加物筛查、食品真伪鉴别和品质评价等方面出发,综述了该技术在食品质量安全检测中的应用。讨论了其应用于食品分析领域时面临的挑战和未来发展趋势。