EFSA Panel on Biological Hazards (BIOHAZ); Scientific Opinion on public health risks represented by certain composite products containing food of animal origin

This Opinion reviews the factors that affect microbial survival and growth in composite products, and in foods in general. It concludes that the main factors to be considered are: water activity, pH, temperature and duration of storage, processing, and intensity and duration of other non-thermal physical processes applied. Prevalence and concentration of the pathogens in food are important to determine the risk for consumers. The opinion presents a review of the quantitative microbiology models and databases that can be used to provide quantitative estimations of the impact of the above factors on the survival and growth of the main bacterial pathogens. In composite products, migration and diffusion of moisture and substances among the ingredients may change their physico-chemical parameters, particularly at the interfaces. Therefore, the assessment of the risk posed by composite products needs to consider the combinations of parameters most permissive to survival and growth of pathogens. Two complementary approaches are proposed for the identification and profiling of microbiological hazards in different specific composite products. The first one is based on past outbreaks and prevalence of hazards in the products and leads to the conclusion that the most frequent hazard-composite product combinations are Salmonella in cakes and bakery products. The second one consists in decision tools based on the impact on the pathogens of food composition and food processing. Categorisation of the risk for composite products requires information on their composition, processing and further handling, which can largely differ for foods belonging to the same category. Further conditions may influence the risk and should be verified, i.e. hygienic conditions during preparation of the composite products and their ingredients, shelf-life conditions, and reliability of cooking by consumers to inactivate pathogens. The decision tools developed apply to all composite products considered by the mandate, as well as to all other foods. © European Food Safety Authority, 201

Thermal inactivation kinetics and thermal physiology of salmonella

Available from British Library Document Supply Centre-DSC:DXN015517 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Thermal inactivation kinetics and thermal physiology of Salmonella.

Microbial thermal inactivation survivor curves (log10 numbers plotted against time) have long been described as maintaining a strictly linear rate of decline. However, much evidence exists which suggests deviation from log-linear kinetics does occur, and that this is not purely the result of experimental procedure as contended by some authors. Here, the shape of inactivation kinetics in Salmonella enteritidis was investigated. A heat challenge method was developed which, as far as could be ascertained, was free from methodological artefacts influencing the shape of survivor curves. High initial cell densities allied to sensitive enumeration resulted in biphasic survivor curves at 60°C. Tailing survivors accounted for approximately 1 in 105 of the initial population and possessed roughly four times the heat resistance. At temperatures 50 to 65°C, the presence of tailing prevented the use of D-values to accurately describe death rates. However, describing survivor curves using a log-logistic model increased data-fit at all temperatures investigated. The biphasic nature of survivor curves was studied closely between 49 and 60°C. It was observed that the extent of tailing was temperature-dependent; as temperature decreased, linearity increased such that at 51°C, survivor curves had no tailing. Studies using S. typhimurium and S. senftenberg 775W revealed similar kinetics. In these salmonellas, survivor curves demonstrated linearity at 54 and 57°C, respectively. The influences of culture age and growth rate on the shape of 60°C-inactivation curves were also investigated. Batch-cultured S. enteritidis cells of various maturities gave rise to survivor curves of differing heat sensitivities. Exponentially growing cells were shown to be the most heat sensitive, while late-stationary phase cells were the only populations to result in non-tailed survivor curves. Carbon-limited continuously cultivated cells demonstrated similar biphasic inactivation kinetics. Predictably, the slowest dilution rate corresponded to the greatest heat resistance. Starved cells produced linear inactivation kinetics that were virtually identical to those of late-stationary phase batch-cultured cells. That tailing in batch cultures was similar to chemostat populations, indicated that possible differences in growth rates in batch-cultured cells could not account for tailing. Furthermore, growth was necessary for tailing to be observed. Investigations into the cause of tailing revealed that these cells were not genetically distinct from the majority population. Instead, it is believed that tailing cells arise following the expression of heat-shock proteins during heating. Partial inhibition of de novo protein synthesis during heating resulted in much reduced levels of tailing. It is proposed that the temperature of inactivation determines the proportion of cells capable of expressing a heat-shock response, such that the temperature at which linearity is achieved corresponds to the point at which all cells are fully heat-shock protected

sj-doc-1-bjo-10.1177_03080226231208717 – Supplemental material for Sensory approaches for adults with severe or profound and multiple learning disabilities: A systematic literature review

Supplemental material, sj-doc-1-bjo-10.1177_03080226231208717 for Sensory approaches for adults with severe or profound and multiple learning disabilities: A systematic literature review by Jennifer Humpheson in British Journal of Occupational Therapy</p

A comparison between the performance of two types of vertical drain beneath a trial embankment in Belfast

A link road is being constructed in Belfast to join the existing Ml and M2 motorways: one section of the road crosses extensive areas of soft alluvium on embankments rising to a height of 8 m above the existing ground level. A site investigation was carried out to determine the strength and consolidation properties of these soft soils. The values of the coefficient of consolidation were such that to construct the embankments in the time available and to ensure the settlements subsequent to the road opening are acceptable some form of ground improvement would be necessary. Vertical drains were considered to be the most appropriate solution to the problem. A site trial was carried out in which two types of vertical drain were installed beneath trial embankments and the drainage characteristics of the soil monitored. The results have shown good agreement between the laboratory and field data. Une route de jonction, destinée à relier les autoroutes existantes Ml et M2, est en voie de construction à Belfast; un tronçon de la route sur des remblais s'élevant à une hauteur de huit mètres au dessus du niveau du sol existant traverse de vastes zones d'alluvions mous. Une exploration in situ a été effectuée afin de déterminer la résistance et les propriétés de consolidation de ces sols compressibles. Les valeurs du coefficient de consolidation étaient telles qu'il fallait prévoir un système d'amélioration du sol pour permettre la construction des remblais dans les délais disponibles et pour assurer les tassements ultérieurs à l'ouverture de la route. On a considéré que les drains verticaux représentaient la solution optimale du problème. Un essai in situ a été effectué: deux types de drain vertical ont été installés sous le remblai d'essai et les caractéristiques de drainage du sol ont été observées. Les résultats démontrent une bonne corrélation entre les données de laboratoire et les données in situ. </jats:p

Associated and non-associated visco-plasticity and plasticity in soil mechanics

The visco-plastic model is established as a realistic general description of soil behaviour as well as a computationally convenient fiction for solving any properly formulated plasticity problem. The Paper focuses attention on simple elastic-ideally plastic formulations in which both associated and non-associated forms of behaviour are assumed. In the non-associated form the usual bounding theorems are not applicable and it is of interest that in some cases collapse situations significantly different from those given by limit theorems are predicted. Also, some problems of strain-dependent plasticity are solved to demonstrate the flexibility of the viscoplastic algorithm. Le modèle viscoplastique constitue une description générale et réaliste du comportement du sol aussi bien qu'un modèle facilement calculable pour résoudre tout problème de plasticité convenablement formulé. L'étude concentre l'attention sur des schémas (ou modèles) où les deux types de comportement (élasticité simple et plasticité idéale) sont pris en compte simultanément ou séparément. Dans les schémas (ou modèles) où les deux types de comportement ne sent pas associés, les théorèmes limites ordinaires ne sont pas applicables et il est intéressant de noter que dans certains cas on prévoit des situations de rupture très différentes de celles données par les théorèmes limites. Il y a également quelques problèmes de déformation plastique qui sent résolus afin de démontrer la flexibilité de l'algorithme visco-plastique. </jats:p