Olivier Rakotonirainy

A segmentation technique to determine fat content in NMR images of beef meat

There is a constant need for new methods of meat-quality evaluation. Recent advances in the area of computer and video processing have created new ways to monitor quality in the food industry. In this paper, we describe an image-processing technique to determine fat content in beef meat. To achieve this, nuclear magnetic resonance (NMR) images of beef meat have been used. The inherent advantages of NMR images are many. Chief among these are unprecedented contrasts between the various structures present in meat, such as muscle, fat, and connective tissue. Moreover, the three-dimensional nature of the NMR method allows the analysis of isolated cross-sectional slices of the meat and the measure of the volumetric content of fat, and it is not limited to measurements of the superficially visible fat. We propose a segmentation algorithm for the detection of fat and a filtering technique to remove intensity inhomogeneities in NMR images, caused by nonuniformities of magnetic field during acquisition. Measurements have been successfully correlated with chemical analysis and digital photography. We also propose a method to quantify the distribution of fat. Our results show that the NMR technique is a promising noninvasive method to determine fat content in meat.

Liquid chromatography "on-flow" 1H nuclear magnetic resonance on native glycosphingolipid mixtures together with gas chromatography/mass spectrometry on the released oligosaccharides for screening and characterisation of carbohydrate-based antigens from pig lungs.

Glycosphingolipids were prepared from pig lung and pooled into two fractions with (i) ≥3 sugar residues, and (ii) ≤3 sugar residues. Oligosaccharides were prepared and used for gas chromatography, gas chromatography-mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. The glycolipid fractions i and ii were further characterised and purified using a novel method based on high performance liquid chromatography “on-flow” proton nuclear magnetic resonance. The LC “on-flow” NMR technique showed good chromatographic separation and gave NMR spectral information which could be used as guidance for pooling of the separated mixture glycolipids. Conventional 1H NMR, thin layer immunostaining, gas chromatography, gas chromatography/mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry were used to characterise the glycolipids and to validate LC-NMR spectral data.

Preservation of rat skeletal muscle energy metabolism by illumination

Skeletal muscle viability is crucially dependent on the tissue levels of its high energy phosphates. In this study we investigated the effect of the preservation medium Perfadex and illumination with Singlet Oxygen Energy (SOE). Singlet oxygen can be produced photochemically by energy transfer from an excited photosensitizer. The energy emitted from singlet oxygen upon relaxation to its triplet state is captured as photons at 634 nm and is here referred to as SOE. Rat hind limb rectus femoris muscles were preserved for five hours at 22 degrees C in Perfadex, saline, SOE illuminated Perfadex or SOE illuminated saline. Extracts of the muscles were analysed by 31P NMR. Data were analysed using two-way analysis of variance and are given as mean values micromol/g dry weight) +/- SEM. The ATP concentration was higher (p = 0.006) in saline groups (4.52) compared with Perfadex groups (2.82). There was no statistically significant difference in PCr between the saline groups (1.25) and Perfadex groups (0.82). However, there were higher (p = 0.003) ATP in the SOE illuminated groups (4.61) compared with the non-illuminated groups (2.73). The PCr was also higher (p < 0.0001) in the SOE illuminated groups (1.89) compared with the non-illuminated groups (0.18). In conclusion, Perfadex in this experimental model was incapable of preserving the high energy phosphates in skeletal muscle during 5 hours of ischemia. Illumination with SOE at 634 nm improved the preservation potential, in terms of a positive effect on the energy status of the muscle cell.

Testing MRI and image analysis techniques for fat quantification in meat science

The world of meat faces a permanent need for new methods of meat quality evaluation. Recent advances in the area of computer and video processing have created new ways to monitor quality in the food industry. Here, the authors describe an image processing technique to determine fat content in beef meat. To achieve this NMR (Nuclear Magnetic Resonance) images of beef meat have been used. The inherent advantages of NMR images are many. Chief among these are unprecedented contrasts between the various structures present in meat, as muscle, fat, and connective tissue. Moreover, the three-dimensional nature of the NMR method allows the analysis of isolated cross-sectional slices of the meat and the measure of volumetric content of fat, no only the superficially visible one. The authors propose a segmentation algorithm for the detection of fat and a filtering technique to remove intensity inhomogeneities in NMR images, cause by non-uniformities of magnetic field during acquisition. Measurements have been successfully correlated with chemical analysis and digital photography. The authors also propose a method to quantify the distribution of fat. Their results show that NMR technique is a promising non-invasive method to determine fat content in meat.

Energy metabolism during microsurgical transfer of human skeletal muscle assessed by high-pressure liquid chromatography and by 31P-nuclear magnetic resonance.

The effect of ischaemia and reperfusion on human skeletal muscle was studied during free vascularised muscle transfer. Muscle biopsy specimens were taken from patients having microsurgical muscle transfer, 18 cases (17 patients; 12 men, 5 women). The biopsies were taken three times: before transfer of the muscle (control), at maximum ischaemic time, and one hour after revascularisation. The biopsy specimens were analysed for purine nucleotides, by high-pressure liquid chromatography (HPLC), and by nuclear magnetic resonance (NMR) at 500 MHz. Phosphocreatine (PCr) recovered only partially (79%) and adenosine triphosphate (ATP) did not differ significantly from normal control after revascularisation and a mean ischaemic time of 114 minutes. NMR measurements showed an accumulation of glucose-6-phosphate (G-6-P) during the ischaemic period, indicating anaerobic metabolism. After three hours of ischaemia and one hour of reperfusion the PCr recovery was less than 60% ( r = 0.7). The results confirm those of previous animal studies, which set three hours normothermic ischaemia as a safe limit for tissue preservation when transferring skeletal muscle. Longer ischaemic times may cause serious postoperative healing problems and reduced muscle function.

Acidic glycosphingolipids of cock testis elucidated by mass spectrometry and NMR spectroscopy

The main acidic glycosphingolipids (GSLs) of cock testis were identified as GalCer I3-sulfate and gangliosides GM4, GM3, GD3 and GT3. They contained N-acetylneuraminic acid as the major sialic acid, and ceramides composed mainly of sphingosine (dl8:1) and C18–24 non-hydroxy fatty acids. Appreciable amounts of hydroxy fatty acids were detected only in the GM4 preparation.