Point Pyrolysis Mass Spectrometry Research Articles

Evaluation of collagen and lipid contents and texture of meat by Curie point pyrolysis–mass spectrometry

The aim of this study was to evaluate the potential of Curie point pyrolysis–mass spectrometry (CpPy–MS) to estimate the collagen and lipids contents and the texture of lamb meat. The work was carried out using the longissimus muscle from 120 commercial lambs originating from different European countries and from contrasting production systems. Meat characteristics varied largely between animals, e.g. 582 (S.D. ± 124) μg hydroxyproline g −1 for collagen content and 22.5 (S.D. ± 9.6) mg g −1 for lipid content, and 2.9 (S.D. ± 1.2) kg cm −2 for shear force value. Non-linear models of prediction were calculated by Artificial Neural Networks (ANNs). The results showed that it is possible to evaluate lipid and collagen contents and meat texture from CpPy–MS fingerprints. The best predictions obtained with test samples were for lipids ( r = 0.89; mean prediction error = 10%), for collagen ( r = 0.85; mean prediction error = 11%) and for texture ( r = 0.78; mean prediction error = 12%).

Curie point pyrolysis–mass spectrometry applied to rapid characterisation of cheeses

The use of Curie-point pyrolysis coupled with mass spectrometry (CpPy–MS) for the rapid characterisation of ‘Camembert’ type cheeses is described. After testing three methods of sample preparation, 5 g of cheese was homogenised in a solution of sodium deoxycholate (3 g l −1). Two microlitres of the resulting cheese suspension was placed on an iron–nickel alloy foil and pyrolysed at 530 °C. The volatile pyrolysis products were then ionised by electron ionisation at 34 eV. The mass spectra thus obtained were considered as ‘fingerprints’ of the analysed cheeses. After several data pre-processing steps a forward stepwise factorial discriminant analysis was used to select a reduced number of mass fragments that allowed a satisfactory classification of the five batches of cheese studied.

Pyrolysis-mass spectrometry characterisation of ovine fat tissues according to diet

The lipids of subcutaneous fat tissues from 120 lambs were analysed by Curie point Pyrolysis - Mass Spectrometry (Py-MS) after extraction of the lipids with hexane. The animals came from six European countries with different production sys- tems. The classification of the fat tissues according to the predominant type of feed the lambs consumed (milk, concentrate or pasture) was obtained by Discriminant Analysis (DAs) and Artificial Neural Networks (ANNs). The classification models were validated by leave-one-out-type cross-validations. The results showed that the Py-MS spectra of the fat tissue lipids permitted recognition of feed type. The percentages of correct classifications determined by cross-validation were 78 % by DA and 92 % by ANNs.

Biodiversity of bradyrhizobia nodulating Lupinus spp.

The genetic structure of Bradyrhizobium isolates recovered from three Lupinus species (Lupinus campestris, Lupinus montanus, and Lupinus exaltatus) grown in Mexico was examined. Among 41 Bradyrhizobium isolates, 18 electrophoretic types (ETs) were distinguished by multilocus enzyme electrophoresis of five metabolic enzymes. The mean genetic diversity, 0.64, indicated that there was great genetic diversity in the population sampled. Most isolates (63%) fell into two closely related clusters (clusters I and II) and were the types most frequently isolated from the root nodules of L. montanus and L. campestris. ET cluster III isolates were frequent nodule occupants of L. exaltatus. The isolates also were assigned to three main groups by using Curie point pyrolysis mass spectrometry. In general, the multilocus enzyme electrophoretic data and pyrolysis mass spectrometric data agreed. We determined the 16S rRNA sequences of representative Lupinus isolates and of Bradyrhizobium japonicum USDA 6T and found that the lupine isolates were highly related to the B. japonicum type strain, although not all B. japonicum type strains (subcultures maintained in different bacterial collections) had identical small-subunit rRNA.

Differentiation of Mycobacterium senegalense from Related Non-chromogenic Mycobacteria Using Pyrolysis Mass Spectrometry

Twenty-six representative strains of Mycobacterium chelonae, Mycobacterium fortuitum, Mycobacterium peregrinum and Mycobacterium senegalense were compared by Curie point pyrolysis mass spectrometry. The M. chelonae and M. senegalense strains formed distinct groups. A third, relatively diffuse group, contained the M. fortuitum and M. peregrinum strains. These results, together with those from corresponding analyses, suggest that pyrolysis mass spectrometry provides a rapid and reliable way of distinguishing between members of closely related mycobacterial species which are difficult to differentiate using conventional taxonomic procedures.