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The potential of Fourier transform mid-infrared spectroscopy (FT-MIR) using an attenuated total reflectance (ATR) cell was evaluated for the authentication of 11 unifloral (acacia, alpine rose, chestnut, dandelion, heather, lime, rape, fir honeydew, metcalfa honeydew, oak honeydew) and polyfloral honey types (n = 411 samples) previously classified with traditional methods such as chemical, pollen, and sensory analysis. Chemometric evaluation of the spectra was carried out by applying principal component analysis and linear discriminant analysis, the error rates of the discriminant models being calculated by using Bayes' theorem. The error rates ranged from

Front-face fluorescence spectroscopy, directly applied on honey samples, was used for the authentication of 11 unifloral and polyfloral honey types (n = 371 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis. Excitation spectra (220-400 nm) were recorded with the emission measured at 420 nm. In addition, emission spectra were recorded between 290 and 500 nm (excitation at 270 nm) as well as between 330 and 550 nm (excitation at 310 nm). A total of four different spectral data sets were considered for data analysis. Chemometric evaluation of the spectra included principal component analysis and linear discriminant analysis; the error rates of the discriminant models were calculated by using Bayes' theorem. They ranged from

Milk samples, collected from nine healthy mid-lactation Holstein cows, were analysed organoleptically by two sensory panels, and chromatographically using mass spectrometry/flame ionization (MSD/FID) and olfactometric detectors. The sensory panels found that the samples collected after the cows were forage-starved for approximately 12 h were of good flavour quality, whereas at least 89% of the samples collected after they were fed baled grass silage were tainted with off-flavour characterized as “feed”. The corresponding MSD/FID chromatograms revealed that 30 min post-feeding samples had significantly ( p 0.05 ) higher concentrations of ethanol, propane-2-one, dimethyl sulphide, butane-2-one, hexanal, heptanal and octane-2,3-dione, whereas 3 h post-feeding samples showed higher concentrations of four of these compounds (propane-2-one, dimethyl sulphide, butane-2-one and hexanal). Olfactometric analysis performed on five milk samples (four off-flavoured and one of good flavour quality) revealed approximately 75 aroma-active compounds. Nearly all these compounds were common to all the analysed milk extracts (both off-flavoured and good quality samples), suggesting that off-flavour originated from the concentration differences of a common set of compounds rather than from the absence or presence of specific compounds.

To establish whether fishy off-flavour observed in cows' milk in Sweden is due to abnormal concentrations of trimethylamine (TMA) in milk, 15 milk samples from 13 cows of the Swedish Red and White breed (SRB) were analysed for this compound using dynamic headspace (DHS) gas chromatography (GC). A mass selective detector (MSD) was used for the qualitative and a flame ionization detector (FID) for the quantitative analyses. Further confirmation was obtained using a solid phase microextraction (SPME) followed by GC-olfactometry (GC-O) and GC-NPD (nitrogen and phosphorus detector). Samples were also evaluated by a two-person organoleptic panel for the presence of fishy off-flavour. Results showed that the seven milk samples with a fish-like taint contained >1 mg TMA/kg milk, whereas, with a single exception, the seven samples that were judged to be normal did not contain this compound. Furthermore, there were indications of a dose-dependent relationship between TMA concentration and fishy off-flavour score.

A simple, rapid, reliable and highly automated analytical method has been developed to determine trimethylamine (TMA) in milk using an MS based electronic nose (SMart Nose). A set of Swedish milk samples with and without naturally occurring TMA was used to compare this new method with sensory analysis and dynamic headspace (DHS) gas chromatography with flame ionisation detection (GC-FID). The results show good agreement between these three analytical methods. A lower detection limit (0.5 mg kg–1) and better repeatability were achieved with this new method compared to both sensory and DHS GC-FID analyses (1–2 mg kg–1). The user-friendly multivariate analysis software provided with the SMart Nose system was used for TMA determination via a numerical PCA. Using Excel, peak intensity, correlated with TMA concentration via a second order equation, gave similar results. Thus, this is an up to date method of choice for the quantitative determination of TMA in milk. It is also able to give further qualitative information on the milk analysed using the PCA analysis supplied with this equipment.

Le present travail actualise un article de synthese paru en 1993 sur ce sujet. Il synthetise les principales nouvelles donnees et connaissances acquises a ce jour, notamment dans le domaine de nouveaux materiaux d'emballage attractifs et prometteurs comme le polyethylene terephtalate (PET). Apres un bref rappel theorique des mecanismes qui expliquent la photo-oxydation des produits alimentaires, notamment les effets conjugues (synergie) de la lumiere et de l'oxygene ainsi que le role cle joue par la riboflavine comme sensibilisateur, il passe ensuite en revue les principaux effets de la photo-oxydation sur les produits laitiers : perte de vitamines, oxydation des lipides insatures, decoloration et apparition de defauts de la flaveur. Dans sa conclusion, ce travail propose un certain nombre de mesures simples et concretes permettant de limiter, voire de prevenir ce type de reaction quant aux choix i) de la lumiere/de l'illuminant utilise(e), ii) de la translucidite et de la permeabilite de l'emballage a l'oxygene et iii) des conditions de stockage.

The current review lists a total of 126 chiral compounds described in the literature for at least 21 different cheese varieties: 30 alcohols, 8 ketones, 2 aldehydes, 20 esters, 20 lactones, 27 carboxylic acids, 13 hydrocarbons (8 terpenes), 4 furanones, and 2 amines. Of these only a few authentic reference compounds are commercially available. All these data are compiled in seven tables.

This preliminary study aims to compare two different extraction and concentration methods often used for the gas chromatographic analysis of volatile components in food to determine the advantages and drawbacks of both for future routine investigation of PDO (protected designation origin) ewes’ milk cheeses. Roncal, Pecorino Sardo and Fiore Sardo were investigated at different ripening stages. The dynamic headspace technique using a Purge & Trap device (DHS) makes it possible to extract more highly volatile compounds than the simultaneous distillation extraction (SDE) method. Consequently, the latter is more efficient for extracting low-volatile components such as phenols, free fatty acids, lactones and longer-chain aldehydes, ketones, alcohols and esters. These two extraction methods are therefore complementary.

The flavour of a typical sample of Gruyere cheese and that of a Gruyere exhibiting a potato-like off-flavour was examined by instrumental and sensory analyses. Based on the results of dynamic headspace gas chromatography-mass spectrometry (DHGC/MS), aroma extract dilution analysis (AEDA) and gas chromatography-olfactometry of static headspace samples (GCO-H), 2-/3-methylbutanal, methional, dimethyltrisulphide, phenylacetaldehyde, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, methanethiol, as well as butyric, 2-/3-methylbutyric and phenylacetic acid form the typical flavour of Gruyere cheese. The potato-like character of the sample showing an aroma defect, however, could not be attributed definitively to one of these compounds. Considering the results of DHGC/MS and AEDA, 2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine could be the possible causes of the off-flavour.

This paper examines the distribution of mono- and sesquiterpene secondary metabolites in 47 plants present in grazing areas from which cheeses are produced. In total, 54 terpenoid volatiles, derived from both highland and lowland plants, were obtained by a gaseous purge-and-trap system without the use of organic solvents and then identified by automated GC/MSD-FID analysis using mass spectral libraries, retention indices, and data acquired by the authors with authentic substances. Single ion monitoring proved valuable in identifying overlapping compounds with similar spectra for the subsequent semiquantitative determination of compositions. These are displayed as radar plots. It is suggested that flavor/aroma differences in cheeses produced from animals grazing in different areas and seasons arise from species (n = 38), phenological stages (n = 8), locations (n = 4), and seasonal variation in terpenoids present (the most common were trans-β-ocimene, limonene, and trans-β-caryophyllene). This hypothesis is...

Resume Le present travail reconsidere les effets de certains procedes de fabrication, de conditions de stockage et de traitements a des fins culinaires de quelques produits laitiers a l'etat frais du commerce susceptibles d'oxyder le cholesterol. Des fromages, des beurres fondus et un lait en poudre frais ou stockes a basse temperature a l'abri de la lumiere et de l'oxygene ne contiennent pas ou que de faibles traces d'oxysterols. Faire fondre des fromages (raclettes) n'en genere pratiquement pas, mais porter un beurre fondu 30 min a 170–175 °C ou plus de 10 min a 205–210 °C en produit. Un stockage de fromages exposes a une lumiere fluorescente (blanc froid) deux a 4 mois a 6 °C et d'un lait en poudre d'une activite en eau de 0.11 1 annee a 30 °C en presence d'oxygene (660 mL/L) peut oxyder 10 a 15% du cholesterol. Ces resultats confirment la bonne stabilite du cholesterol dans les produits laitiers stockes et/ou traites dans des conditions ‘normales’, les conditions extremes envisagees dans ce travail correspondant en fait a des tests acceleres.

Cholesterol oxidation products (COPs) may produce adverse biological effects, and there is increasing concern regarding the potential health implications of these products in the diet. We have developed a GC/MS method allowing the quantification of COPs in commercially available milk powders and infant formulas. Since oxidation artifacts from cholesterol are essentially impossible to avoid, we have used a deuteriated cholesterol probe to precisely monitor the formation of cholesterol oxidative artifacts during all stages of sample analysis. This strategy allowed the determination of the artifactfree cholesterol oxide content of the samples. We found that freshly opened full crea powders which had been packed under inert gas contained only traces of COPs (

A compilation of publications on the analysis and formation of aroma compounds produced by microorganisms used in dairy production is presented. Literature published between 1970 and 1993 is reviewed whereas literature published before 1970 is covered by a bibliography of review articles. Special attention was given to the contribution of lactobacilli, streptococci, lactococci, and bifidobacteria on the formation of volatile aroma compounds in dairy products. Comparative quantitative data including complete citation of the references are listed in tables thus providing a quick access to an area of special interest with the help of key words.

The aim of this study was to test the suitability and performance of various stationary phases and column dimensions for dynamic headspace gas chromatography of food aromas. The trials were performed using an aqueous test mixture containing thirty seven volatile flavor components of intense aroma, and a sample of ripe Swiss Emmental cheese. The best performance with both samples was obtained with a capillary column coated with a thick film of polydimethylsiloxane. This column resolved the greatest number of compounds in the cheese sample and resulted in the overlapping of one pair of peaks only from the test mixture. Because of its other advantages, i. e. high capacity owing to its film thickness, and insensitivity to the high moisture content of some samples or traces of oxygen in the carrier gas, the polydimethylsiloxane column appears suitable for the analysis of the volatile and highly polar compounds present in complex mixtures such as food aroma.

Electronic noses produce data which are difficult to transfer between identical instruments because of differences in the characteristics of "identical" instruments and because of sensor drift. The transportability of data is, however, essential for the setting up of databanks. Results of the present investigation, using processed cheeses and evaporated milk as reference materials, show that data transfer between two electronic noses based on mass spectrometry is possible and simple.

The objective was to determine the influence of the season of manufacture and the ripening time on the volatile terpenoids and benzenoids of La Serena cheese made in summer, winter and spring, using a plant coagulant. Ewes were fed with formulated feed in summer, grazing on natural pastures in winter and spring. Most terpenoids and benzenoids present in cheese were observed in the formulated feed (mainly terpenes), and in the Cynara cardunculus extract (mainly benzenoids). The enantiomeric α(+){plus 45 degree rule}α(-)-pinene ratio changed during ripening. γ-Curcumene, α-humulene, ethyl benzene and propyl benzene and all xylene isomers decreased, while α-terpineol, verbenone, benzyl alcohol, 2-phenyl-ethanol, benzoic acid methyl ester, and the phenolic compounds increased significantly during ripening. Safranal, geranyl acetone, γ-curcumene and α-curcumene were more abundant in spring than in winter cheeses. Alkyl benzenes and other benzenoids were significantly more abundant in summer than in winter or spring cheeses. © 2007 Elsevier Ltd. All rights reserved.

Fourier transform near-infrared spectroscopy (FT-NIR) was evaluated for the authentication of eight unifloral and polyfloral honey types (n = 364 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis. Chemometric evaluation of the spectra was carried out by applying principal component analysis and linear discriminant analysis. The corresponding error rates were calculated according to Bayes' theorem. NIR spectroscopy enabled a reliable discrimination of acacia, chestnut, and fir honeydew honey from the other unifloral and polyfloral honey types studied. The error rates ranged from

A compilation of literature data on the content of cholesterol oxidation products (COP) in various food products and in blood demonstrates a large variation in content in products or tissues of very similar nature when analyzed in different laboratories according to a large number of methods. The lack of validated, internationally recognized methodology with published accuracy and precision has so far hindered such assessments. Hence an interlaboratory comparision of methodologies of COP analysis was undertaken on egg yolk powders (EYP), whole milk powders (WMP), skim milk powders (SMP), and lard (L). Each product type had one fresh sample (low) and one aged (high) in COP contents. A total of 17 sets of results on WMP, 15 on SMP and EYP, and 13 on L were compared. Overall results (mg/kg sample) varied extensively: Fresh EYP 0.72–265, aged EYP 2.51–361; fresh WMP 0.02–18.1, aged WMP 0.02–26.9; fresh SMP 0.02–6.51, aged SMP < 0.01–6.51; fresh L 0.18–97, aged L 4.15–452. Some results were questioned, viz., those from laboratories not indicating substantial differences between samples “low” and “high” in total COP. Others were excluded because of lack of verification of identity of gas chromato-graphic peaks by mass spectrometry. Then a more narrow range of core results (mg/kg sample) was observed: Fresh EYP 5.69–29.5 sample, aged EYP 11.8–79.0; fresh WMP 0.12–1.76, aged WMP 1.17–13.7; fresh SMP < 0.30–

Potent odorants of a typical sample of Gruyere cheese and of a Gruyere exhibiting a potato-like off-flavour were quantified by isotope dilution analysis. The studies of sensory models revealed that 2-/3-methylbutanal, methional, dimethyltrisulphide, phenylacetaldehyde, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, methanethiol, as well as acetic, propionic, butyric, 3-methylbutyric and phenylacetic acids comprise the typical flavour of Gruyere cheese. The potato-like character of one sample showing an aroma defect, however, was mainly attributed to a too high concentration of methional.