Effect of steam, lactic acid and combined treatments for inactivating Campylobacter jejuni inoculated on chicken skin

International audienceno abstrac

Relation between crust development and heterocyclic aromatic amine formation when air-roasting a meat cylinder

The meat crust that develops during cooking is desired by consumers for its organoleptic properties, but it is also where heterocyclic aromatic amines (HAs) are formed. Here we measured HAs formation during the development of a colored crust on the surface of a beef meat piece. HAs formation was lower in the crust than previously measured in meat slices subjected to the same air jet conditions. This difference is explained by a lower average temperature in the colored crust than in the meat slices. Temperature effects can also explain why colored crust failed to reproduce the plateauing and decrease in HAs content observed in meat slices. We observed a decrease in creatine content from the center of the meat piece to the crust area. In terms of the implications for practice, specific heating conditions can be found to maintain a roast beef meat aspect while dramatically reducing HAs content

Multi-response Modelling of the Maillard reaction in a model cheese

International audienceProcessed cheese derives from a secondary milk processing step that involves mixing and heating dairy (cheese, butter and milk powders) and non-dairy products (emulsifiers). This processing yields a homogeneous product, usually spreadable, with a shelf-life often longer than 6 months. During cheese processing and storage, lipid oxidation, caramelization and Maillard reactions occur and produce odour-active compounds. In this study, a methodological approach was used in order to (i) identify odorants responsible for flavor attributes or compouds involved in the reaction chain, (ii) monitor the evolution of these markers during the heat treatment applied to the matrix, (iii) establish an observable reaction scheme and (iv) model and predict the evolution of these compounds during thermal operations. In this aim, a model cheese and a cooking cell were elaborated. Various couplings of gas chromatography with olfactometry were used to identify odorous compounds. Two-dimensional comprehensive chromatography allowed a semi-quantitation of trace and ultra-trace compounds, while precursors were quantitated by high performance liquid chromatography. An observable reaction scheme of the Maillard reaction was extracted from these data and makes the multi-response modeling step possible despite a partial quantitation of the volatile compounds. Finally, we obtained a formal model combining 19 components (including four odorants) connected by 14 stoechiometric balanced reactions. This model makes it possible to predict the evolution of these components depending on the initial content of lactose, galactose and according to the heat treatment applied to the cheese matrix. This work was carried out with the financial support of the ANR-Agence Nationale de la Recherche-The French National Research Agency under the Programme National de Recherche en Alimentation et nutrition humaine , project ANR-06-PNRA-023REACTIAL "Prediction and control of the appearance or disappearance of reactional markers during food process and conservation "

Modelling the Maillard reaction during the cooking of a model cheese

During processing and storage of industrial processed cheese, odorous compounds are formed. Some of them are potentially unwanted for the flavour of the product. To reduce the appearance of these compounds, a methodological approach was employed. It consists of: (i) the identification of the key compounds or precursors responsible for the off-flavour observed, (ii) the monitoring of these markers during the heat treatments applied to the cheese medium, (iii) the establishment of an observable reaction scheme adapted from a literature survey to the compounds identified in the heated cheese medium (iv) the multi-responses stoichiokinetic modelling of these reaction markers. Systematic two-dimensional gas chromatography time-of-flight mass spectrometry was used for the semi-quantitation of trace compounds. Precursors were quantitated by high-performance liquid chromatography. The experimental data obtained were fitted to the model with 14 elementary linked reactions forming a multi-response observable reaction scheme

Integrated approach on heat transfer and inactivation kinetics of microorganisms on the surface of foods during heat treatments: Software development

The objective of this work was to create a software application (Bugdeath 1.0) for the simulation of inactivation kinetics of microorganisms on the surface of foods, during dry and wet pasteurisation treatments. The program was developed under the Real Basic 5.2 application, and it is a user-friendly tool. It integrates heat transfer phenomena and microbial inactivation under constant and time-varying temperature conditions. On the basis of the selection of a heating regime of the medium, the program predicts the food surface temperature and the change in microbial load during the process. Input data and simulated values can be visualised in graphics or data tables. Printing, exporting and saving file options are also available. Bugdeath 1.0 includes also a useful database of foods (beef and potato) and related thermal properties, microorganisms (Salmonella and Listeria monocytogenes) and corresponding inactivation kinetic parameters. This software can be coupled to an apparatus developed under the scope of the European Project BUGDEATH (QLRT-2001-01415), which was conceived to provide repeatable surface temperature-time treatments on food samples. The program has also a great potential for research and industrial applications

Etude bibliographique sur les coefficients de transferts de chaleur et de matière convectifs entre l'air et un ensemble de produits. I. Du cylindre ou de la sphère isolés à un ensemble de deux à quatre de ces objets

National audienceConvective transfer coefficients are commonly used to calculate the fluxes exchanged between air and solids. For a single solid of simple shape, the value and the distribution of the heat and mass transfer coefficients can be inferred from the air flow properties. This review proved that process to be also possible for two to four cylinders or spheres in tandem or side-by-side more than one diameter apart. For those arrangements the evolution of the flow characteristics leads also to the understanding of the transition between the case of the transfer around a single body and the transfer inside a group of bodies. For staggered arrangements or intermediate arrangements the flows are more complex and the papers too few to undertake that scientific process.Les coefficients de transferts convectifs sont couramment utilisés pour estimer les flux échangés entre l'air et des ensembles de solides. Lorsque l'objet est isolé et de forme simple, la valeur et la répartition des coefficients de transferts peuvent être déduites des propriétés de l'écoulement. Cette revue bibliographique montre que ceci est également possible pour deux à quatre cylindres ou sphères disposés en ligne ou côte-à-côte et distants de plus d'un diamètre. Pour ces dispositions, les modifications de l'écoulement permettent aussi de comprendre la transition entre le cas du transfert autour de l'objet isolé et celui qui existe dans les ensembles d'objets. Pour des dispositions en quinconce ou intermédiaires, les écoulements sont plus complexes et les travaux sont à l'heure actuelle trop peu nombreux pour pouvoir entreprendre une telle démarche