830 research outputs found
Nitrocellulose film substrate minimizes fragmentation in matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of triacylglycerols.
No full textThe potential of matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) for the analysis of intact triacylglycerols (TAGs) is generally limited by the extensive in-source prompt fragmentation. The sequential deposition of matrix and TAGs over the stainless steel target precoated with a thin layer of nitrocellulose (NC) drastically reduced fragmentation in the MALDI-TOF MS profiling of oils and fats. The NC MALDI-TOF MS profiles of native and thermally stressed virgin olive oil and butter are reported as case studies, along with test analyses of a standard mixture of mono-, di-, and triacylglycerols. Mass spectra were almost completely devoid of both fragment and matrix ion signals, thus disclosing relevant information, especially in the low molecular mass range. The detection of several partial acylglycerols of low abundance and minor TAGs that are barely observed with other techniques also provided evidence for an increased dynamic range of NC MALDI-TOF MS that was due to the minimization of suppressive effects. The NC film substrate also improved the shot-to-shot and sample-to-sample reproducibility of the ion production through the exhibition of a more homogeneous matrix/analyte cocrystallization, thus enabling MALDI-based measurements to a consistent quantification of TAGs
One-step characterization of triacylglycerols from animal fat by MALDI-TOF MS.
No full textComparative characterization of milk fat, lard, and beef tallow triacylglycerols (TAG) has been achieved by using matrix-assisted laser desorption/ionization–time-of-flight (MALDI-TOF) mass spectrometry (MS). The samples formed characteristic patterns, with major TAG signals differing in quantity and intensity according to the fat. In milk fat, the significant contribution of short-chain fatty acids (C4–C10) extends the TAG number to the C20–C60 range. In lard and beef tallow, C12–C18 fatty acids restrict the range to C48–C54, also typical of vegetable oils. Fats originating from ruminants contain odd TAG missing in lard. Signature TAG were identified for each animal fat. C20–C46 specifically fingerprint milk fat; 52:5, 54:5 and 54:6 TAG mark lard; and 55:0, 55:1, 55:2 and 54:0 TAG typify beef tallow. Fats were also analyzed after hydrogenation or bromination; hydrogenation helped to fingerprint the low-abundant long-chain TAG and to distinguish short-chain native TAG from collision-induced fragments; bromination allowed clear separation of saturated and unsaturated TAG. Differences in the fatty acid composition amongst homologous isobaric TAG of different structures were identified by post-source decay analysis of hydrogenated precursors. MALDI-TOF has provenadvantageous for simultaneously detecting TAG at various unsaturation degrees within different TAG classes (Cn). The data provide insight into animal fat differentiation on a molecular basis, increasing the analytical description to a new level, proving the so far underestimated capacity of MALDI-TOF MS in this field
One-step characterization of triacylglycerols from animal fat by MALDI-TOF MS.
No full textComparative characterization of milk fat, lard, and beef tallow triacylglycerols (TAG) has been achieved by using matrix-assisted laser desorption/ionization–time-of-flight (MALDI-TOF) mass spectrometry (MS). The samples formed characteristic patterns, with major TAG signals differing in quantity and intensity according to the fat. In milk fat, the significant contribution of short-chain fatty acids (C4–C10) extends the TAG number to the C20–C60 range. In lard and beef tallow, C12–C18 fatty acids restrict the range to C48–C54, also typical of vegetable oils. Fats originating from ruminants contain odd TAG missing in lard. Signature TAG were identified for each animal fat. C20–C46 specifically fingerprint milk fat; 52:5, 54:5 and 54:6 TAG mark lard; and 55:0, 55:1, 55:2 and 54:0 TAG typify beef tallow. Fats were also analyzed after hydrogenation or bromination; hydrogenation helped to fingerprint the low-abundant long-chain TAG and to distinguish short-chain native TAG from collision-induced fragments; bromination allowed clear separation of saturated and unsaturated TAG. Differences in the fatty acid composition amongst homologous isobaric TAG of different structures were identified by post-source decay analysis of hydrogenated precursors. MALDI-TOF has provenadvantageous for simultaneously detecting TAG at various unsaturation degrees within different TAG classes (Cn). The data provide insight into animal fat differentiation on a molecular basis, increasing the analytical description to a new level, proving the so far underestimated capacity of MALDI-TOF MS in this field
Functional and technological use of lactobacilli as producers of butyric acid in fermented milk
No full textIntroduction Butyric acid (BA) may exert significant beneficial effects on human health. Recent
studies highlighted that in people with type 1 diabetes, some intestinal bacteria, responsible for
BA production, are absent. For the potential use of one or more bacterial strains as probiotics in
the food industry, the objective of the investigation was to evaluate the ability of the lactic acid
bacteria strains (LABs) to produce BA.
Method UHT skimmed and whole milk were commercial products. The lyophilized cultures
identified with the progressive numbers from 1 to 8 (Lactobacillus asini ssp. Butyricus (1-3),
Lactobacillus plantarum (4-6), Lactobacillus sp. 7-8) were revitalized by individual inoculation.
The inoculum was made at 2% in UHT skimmed and whole milk. After 24 h at 30°C, fermented
milks were distillate and submitted to the determination of BA using gas chromatography
coupled with mass spectrometry (GC/MS) in SIM mode.
Results / Discussion / Conclusion Butyric acid was produced by the LABs in amount not higher
than 0.8 and 15 ppm respectively in skimmed and whole fermented milk samples. When
tributyrin was added in skimmed milk, at the concentration of 5g/L, an average quantity of
85ppm butyric acid was produced. The strains were able to release tenfold higher levels of
butyric acid than in milk, confirming that the lipase activity of some Lb. plantarum strains is
highest on tributyrin. This allows us to conclude that BA in milk inoculated with the eight LAB
strains originated from lipolytic hydrolysis of triacylglycerols and not from fermentation of
sugar
Assessment of milk fat content in fat blends by 13C NMR spectroscopy analysis of butyrate
No full textButyric acid (butyrate) is a candidate marker of milk fat in complex fat blends, since it is exclusive of milk triacylglycerols (TAGs) from different ruminant species. In this work, we determined the amount of milk fat used for the preparation of fat blends by 13C Nuclear Magnetic Resonance (13C NMR) spectroscopybased quantification of butyrate. When tested on fat samples spiked with known amounts of reference bovine milk fat (BCR-519 certified material), the relative composition of the mixtures was reliably assessed through the integration of the diagnostic 13C NMR carbonyl (C1) or a-carbonyl methylene (C2) resonances of butyrate. NMR data exhibited strict correlation with high resolution-gas chromatography (GC) of fatty acid methyl esters (R2 1⁄4 0.99), which was used as an independent and well-established method for the determination of butyrate. Thus, 13C NMR can be used for the direct assessment of milk fat content in fat mixtures, at a limit of detection lower than 5%, with clear advantages over the traditional GC methods in terms of speed, robustness and minimal sample handling. The natural variability of butyrate in milk has been taken into account to estimate the uncertainty associated with the milk fat content in unknown fat blends
Quali-quantitative determination of triglicerydic, fatty acids and CLA in “Mozzarella di Bufala Campana” by high resolution gaschromatography (HRGC)
No full textMozzarella Cheese: quali-quantitative evaluation of triglyceridic and acidic composition (CLA) by High Resolution Gascromatography
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