First Metatarsal Bones as Substitutes for Tibias in Harris Lines Studies on Past Populations

International audienceThe first metatarsal bones (FMBs) are often better preserved than tibias in archeological samples. The aim of this study was to test the possibility of performing Harris lines studies on FMBs as stress markers instead of tibias. The Harris lines in 264 FMBs from a historic French burial site dating back to two burial periods were studied and compared with the Harris lines in FMBs from 4 historical and 2 Neolithic sites. The Harris lines in 57 tibias and FMBs were compared.The intra-observer, inter-observer, side, and age-at-death variations were not found to be significant. The total prevalence of Harris lines was lower in the 16th-17th century sample than in the 11th-13th century sample, but no significant diachronic variations were observed between male and female samples. The Harris lines in the tibias and FMBs were not significantly correlated. Comparisons on the prevalence of the Harris lines showed the existence of significant differences between several samples, in keeping with the archeological data. In conclusion, the Harris lines in the first metatarsal bonesstudied showed significant intra- and inter-population variations. Further investigations are now required, however, to precisely access the value of using first metatarsals instead of tibias for Harris lines studies in bioarcheology or perhaps acknowledge that Harris lines have minimal scientific use as stress markers, except in unusual situations

Effect of pH on the heat resistance of spores Comparison of two models

International audienceAll published models describing the effect of pH on the heat resistance of spores can be regarded either as a linear first degree equation or a linear second degree equation. This work aimed to compare both models from 3 sets of published data for , Clostridium sporogenes and Bacillus stearothermophilus respectively. The relative quality of fit of each model with respect to the other depends on the species, the strain and the heating temperature. Parameter estimation was more reliable for the second degree model than for of the simple first degree equation. However, in the case of acidic foodstuffs, predictions obtained from the second degree model are more sensitive toward errors of parameter values. The second degree model is better from the point of view of safety at most frequent ranges of pH of foods. Moreover, for Clostridium botulinum , the goodness of fit of this model is clearly higher than that of the first degree equation. If this observation is confirmed by further work, the second degree model in application of standard calculations of heat processes of foods would be preferred

Quantifying the combined effects of the heating time, the temperature and the recovery medium pH on the regrowth lag time of Bacillus cereus spores after a heat treatment

International audienceThe purpose of this study was to quantify the lag time of re-growth of heated spores of Bacillus cereus as a function of the conditions of the heat treatment: temperature, duration and pH of the recovery medium. For a given heating temperature, curves plotting lag times versus time of heating show more or less complex patterns. However, under a heating time corresponding to a decrease of 2 decimal logarithms of the surviving populations of spores, a linear relationship between the lag time of growth and the time of the previous heat treatment can be observed. The slope of this linear relationship followed itself a Bigelow type linear relationship, the slope of which yielded a - value very close to the observed conventional z-value. It was then concluded that the slope of the regrowth lag time versus the heating time followed a linear relationship with the sterilisation value reached in the course of the previous heat treatment. A sharp effect of the pH of the medium which could be described by a simple "secondary" model was observed. As expected, the observed intercept of the linear relationship between lag time and heating time (lag without previous heating) was dependent on only the pH of the medium and not on the heating temperature

Survival curves of heated bacterial spores: effect of environmental factors on Weibull parameters

International audienceThe classical D-value of first order inactivation kinetic is not suitable for quantifying bacterial heat resistance for non-log linear survival curves. One simple model derived from the Weibull cumulative function describes non-log linear kinetics of micro-organisms. The influences of environmental factors on Weibull model parameters, shape parameter "p" and scale parameter "delta", were studied. This paper points out structural correlation between these two parameters. The environmental heating and recovery conditions do not present clear and regular influence on the shape the parameter "p" and could not be described by any model tried. Conversely, the scale parameter "delta" depends on heating temperature and heating and recovery medium pH. The models established to quantify these influences on the classical "D" values could be applied to this parameter "delta". The slight influence of the shape parameter p variation on the goodness of fit of these models can be neglected and the simplified Weibull model with a constant p-value for given microbial population can be applied for canning process calculations

Quantifying the effects of heating temperature, and combined effects of heating medium pH and recovery medium pH on the heat resistance of Salmonella typhimurium

International audienceThe influence of heating treatment temperature, pH of heating and recovery medium on the survival kinetics of Salmonella typhimurium ATCC 13311 is studied and quantified. From each non-log linear survival curve, Weibull model parameters were estimated. An average shape parameter value of 1.67 was found, which is characteristic of downward concavity curves and is in agreement with values estimated from other S. typhimurium strains. Bigelow type models quantifying the heating temperature, heating and recovery medium pH influences are fitted on scale parameter δ data (time of first decimal reduction), which reflects the bacterial heat resistance. The estimate of zT (4.64 °C) is in the range of values given in the literature for this species. The influence of pH of the heating medium on the scale parameter (zpH: 8.25) is lower than that of the recovery pH medium influence (z′pH: 3.65)

Modelling the influence of palmitic, palmitoleic, stearic and oleic acids on apparent heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3

International audienceHeat resistance of spores is affected by many factors such as temperature, pH, water activity (aw) and others. Previous studies have reported that free fatty acids can affect the germination and growth of bacterial spores. In this study, we investigated the influence of free fatty acids in heating medium or in recovery medium on the heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3. Four free fatty acids were studied: palmitic, palmitoleic, stearic and oleic acid. During thermal treatments, the impact of these FFA in heating media was generally low, but the presence of free fatty acids in the recovery medium highly decreases bacterial spore apparent heat resistance, particularly with unsaturated fatty acids. A mathematical model was developed to describe and quantify the influence of free fatty acids in recovery media on the D-values. The z'FFA parameter values which quantify the impact of free fatty acids were determined. The variation of this parameter value according to the free fatty acid type was compared with MIC value variation given in the literature. The model enables the decrease in D-values in the presence of free fatty acids to be estimated. The high concentrations of free fatty acids in liver or canned duck may explain the microbial stability with low sterilization values applied

Application pratique de la méthode d’estimation de l’âge au décès de Schmitt et Broqua (2000)

Cette étude tend à confronter la méthode d’estimation de l’âge au décès proposée par Schmitt et Broqua (2000) à la réalité archéologique de la population d’une nécropole historique. Le grand nombre de bassins étudiés (940) permet une approche statistique de l’estimation d’âge proposée, en particulier sur la conservation des os coxaux et sur les différences d’estimation entre les côtés droit et gauche. Finalement, la méthode semble assez bien adaptée à l’étude d’une population archéologique bien que les différences entre les côtés ne soient pas négligeables

Application pratique de la méthode d’estimation de l’âge au décès de Schmitt et Broqua (2000)

Cette étude tend à confronter la méthode d’estimation de l’âge au décès proposée par Schmitt et Broqua (2000) à la réalité archéologique de la population d’une nécropole historique. Le grand nombre de bassins étudiés (940) permet une approche statistique de l’estimation d’âge proposée, en particulier sur la conservation des os coxaux et sur les différences d’estimation entre les côtés droit et gauche. Finalement, la méthode semble assez bien adaptée à l’étude d’une population archéologique bien que les différences entre les côtés ne soient pas négligeables

Traitement d'images scanographiques appliqué à l'étude tridimensionnelle de l'évolution de la forme du crâne humain

Extended proceedings of the workshop organized in May 1999.National audienceWe present an automatic method that allows one to visualize and analyze, in three dimensions, the evolution of the shape of the human skull from CT-Scan images. A first algorithm automatically extracts the crest lines from CT-Scan images of the skull of a modern Man and of a cast of a skull of a prehistoric Man. Those lines correspond to the salient lines of the skull surface. They will be used as landmarks to automatically find the homology points between the two skulls. Based on these couples of matched points, we compute a volumetric transformation that superposes the two skulls. This transformation can be interpolated to obtain intermediary transformations. We extract then a surface model of the skull of the modern Man and we apply successively the intermediary transformations to visualize the evolution of the sull between the prehistoric and the modern Man. We have applied this method to the skull of the Man of Tautavel, dated of about 450 000 years, and we present future applications in facial reconstruction and tridimensional morphometry.Nous présentons une méthode automatique qui permet de visualiser et d'analyser, en trois dimensions , l'évolution de la forme du crâne humain à partir d'images scanographiques. Un premier algorithme extrait automatiquement des lignes de crête à partir des scanographies d'un crâne d'un Homme moderne et du moulage du crâne d'un Homme préhistorique. Ces lignes correspondent aux lignes saillantes de la surface crânienne. Elles servent de repères à un algorithme de mise en correspondance pour trouver automatiquement les points homologues entre les deux crânes. A partir de ces points appariés, on calcule une transformation de l'espace qui superpose les deux crânes. Cette transformation peut ensuite être interpolée pour créer des transformations intermé-diaires. A partir de l'image scanographique, on extrait alors un modèle surfacique du crâne de l'Homme moderne auquel sont successivement appliquées les transformations intermédiaires pour visualiser l'évolution du crâne entre l'Homme préhistorique et moderne. Nous appliquons cette méthode au crâne de l'Homme de Tautavel, daté d'environ 450 000 ans, et nous présentons des applications futures en reconstruction faciale et en analyse morphométrique tridimensionnelle

Validation of an overall model describing the effect of three environmental factors on the apparent D-value of Bacillus cereus spores

International audienceSeveral factorial models extending the famous Bigelow model to describe the influence of the heating and recovery pH and aw conditions on bacterial heat resistance have been developed. These models can be associated in an overall multifactorial model describing the influences of heating and recovery conditions on D values. For Bacillus cereus strain ADQP 407 the mo D el parameters characterising the environmental factor influences (pH, Temperature, aw) were evaluated. Determination of bacterial heat resistance in cream chocolate have been realised to validate these parameter values and to evaluate the level of the influence of food texture or different compounds not taken account of in the model