Inaug.-diss.--Giessen. / Lebenslauf. "Literatur": p. [145].

A range of nitrosylmetalloporphyrin complexes, M(porph)NO [M = Fe, Co; porph = TPP, OEP, T[PIV]PP], some labelled with [15]NO, has been synthesised and investigated as structural and spectroscopic models of the cured meat pigment, nitrosylmyoglobin. The nitrosylmetalloporphyrins were found to be unstable in solution (and some in the solid state) with respect to loss or further reaction of the nitrosyl ligand. The diamagnetic cobalt (III) porphyrin nitrosyIs and a range of other square pyramidal complexes of cobalt(III) with an apical nitrosyl ligand have been further investigated by [15]N and [59]Co NMR spectroscopy to establish whether the CoNO group is bent or linear and to study nephelauxetic and spectrochemical effects at the metal. In all cases studied the CoNO group is bent (CoNO ~ 120°). The basal ligands were dithiocarbamate, tetradentate Schiff base, porphyrin, and bidentate diamine and oximate giving S[4], S[2]N[2], N[4], OONN, or ONON coordination in the equatorial plane. The shielding of both cobalt and nitrogen tends to decrease with decrease in M(d) to pi* (NO) back-bonding as indicated by M-N and N-O bond distances, and the MNO angle and the NO stretching frequencies. The shieldings decrease with electron withdrawal by ring substituents and also in going from sulphur to nitrogen to oxygen coligands, i.e. with decrease in ligand field splitting and in the nephelauxetism of the coligands. The bent nitrosyls of cobalt can function as oxygen transfer catalysts via a nitrosyl-nitro couple. Consequently, a range of Co(III) porphyrin nitro complexes, (L)Co(porph)NO[2] (porph = TPP, OEP; L = py, 1Melm) and several nitro complexes containing the other basal ligands have been synthesised and investigated by the [15]N and [59]Co NMR technique. The coordinated nitro ligand is labile and linkage isomerism and ligand exchange have been observed. These observations may be related to the deterioration of cured meat colour which is of importance to the food industry. The crystal structure of (py)Co(TPP)NO[2] is presented; the nitro group of which is rotationally disordered. Recrystallisation of (1MeIm)Co-(TPP)NO[2] gave [Co(TPP)(1Melm)[2]]NO[2], the crystal structure of which has been determined. Formation of this nitrite is further evidence for the lability of the nitro ligand. The known complex Fe(salphen)NO was prepared using ascorbic acid for the first time to prevent contamination with the oxo-bridged iron(III) dimer. Variable temperature [57]Fe Mossbauer effect studies of the S = 1/2 to S = 3/2 spin transition for Fe(salphen)NO show that the crossover is continuous and centred at T[c] ~ 181 K, and that the electronic transition between the two spin states is rapid on the Mossbauer timescale. The fluxionality of CoCl[2]([15]NO)(PPh[2]Me)[2] was studied by variable temperature [15]N and [31]P NMR. An [17]O NMR study of the ?-peroxo complex [(NH[3])[5]Co[17]O[2]Co(NH[3])[5]](NO[3])[4]. 2H[2]O is presented. An attempt to measure [15]N NMR spectra of the diamagnetic 18 electron species, Fe(porph)([14]NO)([15]NO) (porph = TPP, OEP) presumably containing linear FeNO[+] and bent FeNO[-] was unsuccessful.

Cette thèse s’articule autour de 3 parties. Dans la première (épidémiologie descriptive), nous avons évalué, sur un large échantillon d’adultes français (cohorte NutriNet-Santé), la prise de compléments alimentaires et les facteurs associés en population générale et dans des groupes spécifiques (fumeurs, femmes enceintes, sujets atteints de cancer). La prise de compléments, souvent en automédication, était très répandue, en particulier chez les femmes enceintes et les sujets atteints de cancer. Nos travaux suggèrent que les pratiques « à risque » de consommation de compléments alimentaires étaient loin d’être négligeables dans certains groupes. Dans la seconde partie (épidémiologie étiologique), nous avons mis en évidence, pour la première fois, un potentiel effet modulateur d’une supplémentation en antioxydants (essai randomisé SU.VI.MAX) sur les relations prospectives entre consommation de charcuteries et risque de cancer du sein d’une part et taux d’acides gras plasmatiques et risque de cancer (toutes localisations et du sein) d’autre part, en cohérence avec les études mécanistiques. Nos résultats suggèrent que les antioxydants pourraient contrecarrer certains effets potentiellement pro-cancérigènes des charcuteries sur le risque de cancer du sein, et pourraient modifier les associations acides gras – cancer en s’opposant aux effets potentiels des acides gras sur la carcinogénèse. Enfin, la troisième partie de ma thèse a consisté en des travaux méthodologiques transversaux en e-épidémiologie portant sur les compétences informatiques des participants à la web-cohorte NutriNet-Santé. Ces travaux méthodologiques sont nécessaires à la bonne conduite des études épidémiologiques descriptives ou étiologiques en e-épidémiologie nutritionnelle. Les résultats de cette thèse soulignent l’importance de la prise en compte des consommations de compléments alimentaires en épidémiologie et contribuent plus généralement à une meilleure connaissance de l’étiologie des cancers. Ils permettront, à terme, d’améliorer les recommandations en matière de prévention nutritionnelle des cancers. / This thesis is structured in three parts. In the first part (descriptive epidemiology), we assessed dietary supplement use and associated factors in the general population and in specific subgroups (smokers, pregnant women and cancer survivors) of a large sample of French adults (the NutriNet-Santé cohort). Dietary supplement use was widespread, often in self-medication, particularly in pregnant women and in cancer survivors. Our findings suggest that the frequency of risky practices of dietary supplement use were su bstantial in several subgroups. In the second part (etiological epidemiology), we highlighted, for the first time, a potential modulatory effect of an antioxidant supplementation (SU.VI.MAX. trial) on prospective relationships between processed meat intake and breast cancer risk and between levels of plasma fatty acids and cancer risk (overall and breast), in line with mechanistic studies. Our results suggest that antioxidants may counteract the potential procarcinogenic effects of processed meat on breast cancer risk and may modify associations between fatty acids and cancer risk by counteracting the potential effects of these fatty acids on carcinogenesis. Finally, the third part of my thesis pertained to a methodological work in the field of e-epidemiology, related to computer literacy of participants of the NutriNet-Santé web-cohort. These results will be useful for optimizing descriptive and etiological epidemiological studies in nutritional e-epidemiology. Overall, these PhD findings underline the importance of taking into account dietary supplement use in epidemiological studies and contribute to a better understanding of cancer etiology. More general ly, they will also contribute to optimize nutritional recommendations for primary cancer prevention.

Master of Science / Food Science Institute / Kadri Koppel / Oxidation of meat decreases consumer acceptance and reduces market value making it an important problem for the meat industry. Odor and flavor of meat are significantly affected by lipid oxidation and researchers continue to explore new ways to control meat oxidation. Natural antioxidants, irradiation and oxygen treatments are major areas of research in meat lipid oxidation. In recent studies researchers have been exploring ways to extend shelf life of meat and in many case rely on sensory results. This report deals with sensory methods used to measure changes associated with treatments and outlines how researchers are using these methods.

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This study investigated the effects of electrical stimulation (ES), age and weight at slaughter, breed type, post-freezing ageing, and the proteolytic extract of Solanum dubium (Gubbain) seeds on the carcass and meat quality of Sudanese Baggara cattle in Sudan. The study also assessed the microstructural and biochemical properties of Afrikaner x Bonsmara crossbred steer muscles treated with the Gubbain protease in South Africa. In order to achieve these goals, three trials were conducted. In the first trial, eighty Baggara cattle were selected according to breed type and age. The cattle (expermintal animals) were divided into two equal groups that were representative of the typical white Nyalawi breed type (n = 40) and typical red Mesairi breed type (n = 40). Each breed type was divided into two age groups: 20 bulls of about 5 to 5.5 years old, weighing between 280 and 310 kg; and 20 bulls of about 4 to 4.5 years old, weighing between 240 and 260 kg. The bulls were slaughtered and dressed according to the standard Halal method. Electrical stimulation (110 V for 30 seconds) was randomly applied to 50% of the carcasses in each group at 20 minutes post mortem (pm). The carcasses were stored in a chiller (2-4°C) within 45 minutes post mortem. Carcass pH and temperature were recorded at 0.17, 1, 3, 6, 9, 12, and 24 hours pm. Samples of m. longissimus dorsi (LD) were collected for meat analyses. Meat colour (L*, a*, b*, chroma, hue) was measured at 24 hours pm, and then each sample was labelled and put in a plastic bag and frozen at -20°C until processing. The frozen samples were thawed and cut into two equal steaks. Half of the steaks were immediately analysed, while the rest were aged at 4°C for seven days and then analysed. The samples were analysed for instrumental colour, water-holding capacity (WHC), cooking loss (CL), Warner-Bratzler shear force (WBSF) values, and sensory quality. The second trial was for exploratory purposes, while the third trial was for detailed analyses. In the second trial, thirty LD were sampled at 24 hours pm from two age groups of Sudanese Baggara bulls. The ultimate pH and instrumental colour were determined at 24 hours pm. The beef LD samples were each cut into two steaks and randomised into two treatments injected with the Gubbain protease extract (10 per cent muscle weight) and left as a control. The steaks were incubated at 4oC for 24 hours, after which they were analysed for pH, colour, CL, WBSF and sensory quality. The third trial was conducted on muscles from Afrikaner x Bonsmara crossbred steers to study the efficacy of the Gubbain protease extract injection in muscle tenderisation. Twelve m. longissimus thoracis et lumborum (LTL) steaks were sampled from both sides of several carcasses at 24 hours pm. Each steak was cut into two equal samples and then randomised for treatments (injection with Gubbain protease extract vs no injection). The steaks were incubated at 4oC for 24 hours. They were then analysed for colour, sarcomere length (SL), myofibril fragment lengths (MFLs), WBSF, collagen solubility, muscle fibre types, quantification meat degradation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results suggest that ES, animal age and weight affected meat quality attributes, while breed type had no significant effect. ES hastened the rate of pH decline significantly up to 24 hours pm. The ES of the Sudanese Baggara beef carcasses and the use of lighter and younger bulls showed higher L* values, lower a* values, higher hue values, and lower values for WBSF. The carcasses of the Mesairi breed type responded better to ES in terms of tenderness than those of the Nyalawi breed type. The meat from electrically stimulated carcasses resulted in lower WHC with no effect on CL, compared with non-electrical stimulation (NES) carcasses. The WHC of the meat improved as age and weight at slaughter increased. No risk of cold shortening was observed in any of the treatment groups. Although post-freezing ageing showed a negative influence on meat colour stability, it resulted in lower shear force values, which suggest more tender beef. Panellists did not recognise any variations in meat sensory quality between the two age groups. In contrast, the differences in sensory tenderness and overall acceptability due to post mortem interventions (ES and enzymatic protease) were detected. The meat injected with the Gubbain protease extract reduced the WBSF values by 62 to 65% compared with the non-injected samples. The Gubbain protease treatments increased b* values, cooking losses, and the sensory juiciness, tenderness, and overall acceptability of the beef. The injection with the protease extract showed better L* values compared with the control samples. Muscle samples treated with Gubbain protease had shorter MFLs (23.65 ± 3.22 vs 33.09 ± 2.33), probably due to the increased proteolytic activity, and also showed lower WBSF values (1.95 ± 0.70 vs 5.13 ± 1.01) than those samples from the control group. The muscles treated with the protease extract had a higher percentage of collagen solubility (36.30%) than the control muscles (18.40%). The muscle fibres from the treated samples with the Gubbain protease had more breaks and fractures than those from non-injected samples. The SDS-PAGE pattern of the LTL samples showed losses in the higher molecular weight fractions, accompanied by the appearance of many new lower molecular weight bands after treating the muscle with the Gubbain protease extract. The study has shown that there is potential to improve the quality of beef of Sudanese Baggara cattle types if certain interventions (ES, slaughtering younger and lighter bulls, post-freezing ageing, and injection with Gubbain protease) are used. The study also paved the way for a novel and promising meat tenderiser for the beef industry. / Thesis (PhD (Animal Science))--University of Pretoria, 2020. / University of Pretoria (UP) Postgraduate Research Support Bursary Prof. Webb’s meat science research fund at the University of Pretoria / Animal and Wildlife Sciences / PhD (Animal Science) / Unrestricted

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