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International audience; Alcoholic fermentation in oenological conditions is a biological process carried out under significant physiological constraints: deficiency of nitrogen and others nutriments (vitamins, lipids …) and different stresses (pH and osmotic). In literature, few models were proposed to describe oenological fermentations. They are focused on initial conditions and did not integrate nitrogen addition during the fermentation process which is a widespread practice. In this work, two dynamic models of oenological fermentation are proposed to predict the effects of nitrogen addition at two different timings: at the beginning of the process and during the fermentation experiment. They were validated and compared against existing models showing an accurately fit to experimental data for CO2 release and CO2 production rate.

Vial design features can play a significant role in heat transfer between the shelf and the product and, consequently, in the final quality of the freeze-dried product. Our objective was to investigate the impact of the variability of some geometrical dimensions of a set of tubing vials commonly used for pharmaceuticals production on the distribution of the vial heat transfer coefficients (Kv) and its potential consequence on product temperature. Sublimation tests were carried out using pure water and 8 combinations of chamber pressure (4-50 Pa) and shelf temperature (-40°C and 0°C) in 2 freeze-dryers. Kv values were individually determined for 100 vials located in the center of the shelf. Vial bottom curvature depth and contact area between the vial and the shelf were carefully measured for 120 vials and these data were used to calculate Kv distribution due to variability in vial geometry. At low pressures commonly used for sensitive products (below 10 Pa), the vial-shelf contact area appeared crucial for explaining Kv heterogeneity and was found to generate, in our study, a product temperature distribution of approximately 2°C during sublimation. Our approach provides quantitative guidelines for defining vial geometry tolerance specifications and product temperature safety margins.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 777657; Freezing is the most used bacterial cell preservation technique yet still a process that can be damaging and lead to cell death. Cryosensitivity greatly varies depending on considered species or strains. Fourier Transform Infra-Red (FTIR) spectroscopy is a powerful technique allowing biochemical characterization of major cellular components (lipids, proteins, polysaccharides). However, the exploitation of bacterial spectral features under native aqueous environments is challenging due to the strong absorption of water in the mid-IR region. The identification of cryoresistance markers has thus so far been mainly done using FTIR spectra of dried cells. In this study, three lactic acid bacteria strains were selected for their contrasting cryo-sensitivities. The objective was to combine two complementary approaches: a dynamic approach that measures evolution of peak positions in the lipid region of IR spectra as a function of temperature, and a novel approach using a FTIR microscope enabling higher spatial resolution of cells (~103 to 104 cells) in an aqueous environment. The most cryoresistant strain displayed a strikingly different membrane lipid phase transition compared to the other two: although phase transition happened very abruptly and at a low temperature (-14 °C), in gel phase, lipid membranes of the resistant strain maintained a higher degree of disorganization. These observations could be attributed to high unsaturated fatty acid content (>66% of C18:1). In addition to confirming the lipid membrane’s role in cryoresistance, this study has brought to light the potential role of other cellular components by removing the spectral contribution of water in spectra obtained with the FTIR microscope. This was achieved using a specially developed Matlab program, providing access to a large spectral region encompassing both the protein and carbohydrate regions (1800–975 cm-1). Good discrimination and visualization of population heterogeneity was observed, indicating that markers outside the lipid region must also contribute to cryoresistance

[EN] Freeze-drying is a dehydration method suitable for the stabilization of heat-labile pharmaceutical products, such as vaccines. Due to the vial-to-vial variability of heat and mass transfer during the process, the value of the critical process parameters (e.g., product temperature, sublimation rate) may be different between vials and batches often present significant product quality heterogeneity. The aim of this work was the development of a dynamic, multi-vial mathematical model making it possible to predict risk of failure of the process, defined as the percentage of vials potentially rejected by quality inspection. This tool could assist the design of freeze-drying cycle., This work was sponsored by GlaxoSmithKline Biologicals SA which was involved in all stages of the study conduct and analysis

Can the desorption kinetics explain the residual moisture content heterogeneity observed in pharmaceuticals freeze-drying process?. 6. European Drying Conference: EuroDrying 2017

Eco-design of food and bio-processes: Example of production of stabilized lactic acid bacteria. Lecture at WUR

A multidisciplinary approach combining physiology and physical chemistry and associating experimental measurements with in silico modelling was applied to explain the release of aroma compounds during food consumption. Experimental release kinetics obtained by inhaling gaseous samples through controlled protocols highlighted different release behaviours, depending on aroma compound properties. The associated mathematical model described mass transfer mechanisms between the different compartments of the naso-oro-pharyngeal cavities and included both physicochemical and physiological parameters. One of the main developments was notably to consider the possible retention of aroma compounds by wetted mucosa. Model sensitivity analysis confirmed the key role of interaction between aroma compounds and mucosa (air/mucosa partition coefficient) and of individual breath parameters (current breath volume and respiratory frequency) on the persistence of aroma compound in exhaled air. These achievements show that the association of an experimental approach and mechanistic modelling constitutes a powerful tool to improve the understanding of aroma release and persistence.

The aim of this study was to gain knowledge about the role of triacylglycerol (TAG) composition in fatty acids (FA) of o/w emulsions on both the pancreatic lipolysis kinetics and the bioaccessibility of released products (i.e. contained within the bile salt micellar phase). A mathematical model was developed and its predictions were compared to a set of experimental data obtained during an in vitro digestion of a whey protein stabilized emulsion. Modeling results show that FA residues of TAG were hydrolyzed at specific rates, inducing different bioaccessibility kinetics. The estimated lipolysis rate constants of the studied FA (C8:0, C10:0 >> C18:1 n-9 >> C12:0 > C14:0 > C16:0 approximate to C16:1 n-7 > C22:6 n-3) were in close agreement with the available literature on the substrate specificity of pancreatic lipase. Results also suggest that lipolysis products are very rapidly solubilized in the bile salt mixed micelles with no fractionation according to the FA carbon chain.

Ce numéro d'Innovations Agronomiques comprend les articles correspondant aux présentations du colloque « Comprendre et utiliser la structure des aliments pour améliorer leurs qualités nutritionnelles et sensorielles » qui s'est tenu à Rennes le 13 mai 2014.; The design of food, as smart vectors of target molecules responsible for both sensory and nutritional properties, is a major challenge for the food industry. The aim is to provide good and healthy foods,based on the specific needs of populations (children, athletes, elderly or overweight people). The digestive tract, from the mouth to the intestine, can be considered as a multistep reactor, compact and perfectly adaptable. During this process, i) the structure and therefore the physical characteristics of the bolus, and ii) the physiological characteristics of the individual impact the kinetics of digestion and influence the physiological control related to health and well-being. Mathematical modeling of transfers and reactions in the digestive tract is an original and powerful approach. It allows the decoupling of mechanisms linked to the structure and composition of the food on the one hand and to the physiology of individual on the other hand. It thus provides a basis for building tools to help in the food designing. This approach, coupling in vitro and in vivo experiments and in silico developments, is illustrated through three examples based on dairy products of different composition and structures (model gels, cheeses, yogurts) in order to predict the flavour perception (salt and aroma) and the digestion of proteins.; La conception d'aliments, en tant que vecteurs intelligents de molécules cibles responsables aussi bien de propriétés sensorielles que nutritionnelles correspond à un enjeu majeur pour l'industrie alimentaire. Il s'agit de proposer des aliments avec des teneurs réduite en sel, sucre ou matière grasse, ou bien enrichis en fibres ou protéines, et ceci en intégrant les besoins spécifiques des populations (enfants, sportifs, personnes agées ou en surpoids ...). Le tube digestif, de la bouche jusqu'à l'intestin, peut être considéré comme un formidable réacteur multi étagé, compact et parfaitement adaptable. Au cours de ce processus, la structure et donc les caractéristiques physiques du bol alimentaire, ainsi que les caractéristiques de l'individu qui consomme l'aliment impactent les cinétiques de digestion et influencent les régulations physiologiques associées à la santé et au bien-être de l'Homme. La modélisation mathématique des réactions et transferts dans le tube digestif constitue une approche originale et puissante, car elle permet de découpler les phénomènes liés à la structure et la composition de l'aliment d'une part et à l'individu d'autre part. Elle constitue ainsi une base pour construire des outils d'aide à la formulation. Des approches couplant mesures in vitro et in vivo associées à des développements in silico sont illustrées au travers de trois exemples sur des produits laitiers de différentes structures et compositions (gels laitiers modèles, yaourts et fromages), et ceci afin de prédire la perception salée, la perception d'arômes et enfin la digestion de protéines.

Developing smart control strategies of freeze-drying of lactic acid bacteria. 5. International Conference on Lyophilization and Freeze Drying

International audience

International audience

International audience; On the basis of a first mechanistic model predicting aroma release in the oropharynx during food consumption, the aim of the present work was to improve its accuracy and to use it to identify the main mechanisms responsible for in-mouth aroma release. Comparison between predicted release kinetics and the ones measured by APCI-MS in the nasal cavity of subjects eating flavoured yogurt highlighted the reasonably accurate time predictions of the relative aroma concentration in the nasal cavity and the model ability to simulate successive swallowing events as well as partial velopharyngeal closure. Parameters identified as the most influent for in-vivo aroma release were related to either physico-chemistry (equilibrium air/product partition coefficient, mass transfer coefficient in the product), physiology (the volume of the nasal cavity, breath airflow rate) or interaction between both (the amount of residual product in the pharynx, air/product contact area).

International audience

International audience

International audience

A model predicting the weight loss and the dry matter increase in the core and in the rind of a French smear soft cheese (Munster type) has been developed. Experimental data were collected from experiments carried out in an aseptic pilot scale ripening chamber under nine different combinations of temperature (8, 12 and 16 °C) and of relative humidity (85%, 93% and 99%) according to a complete experimental design. For each run 16 samples were analysed at various ripening stages. The model took into account the water loss by evaporation, the water transfer from the core to the surface and the mass loss due to the CO2 release. The cheese weight loss was more influenced by the relative humidity than by the temperature. The model was able to account for the experimental weight loss as well as the rind and the core dry matter, with accuracy acceptable for practical use.

International audience

International audience

National audience

Mass yield and operating time for a pork meat dehydration–impregnation–soaking (DIS) process were optimized using a coupled genetic algorithm/sequential quadratic programming method in order to obtain the optimal operating conditions: temperature and soaking solution concentrations. The DIS process was simulated by a neural network model. The non-linear optimization problem was constrained to ensure the main product characteristics: stability indicated by the water activity target and flavour characterized by the phenol gain target. The climatic conditions, the model validity region, the raw material costs and the operator working schedule were taken into account. Optimal solutions are discussed for three different batch configurations: single-stage processing under constant conditions, single-stage processing under varying temperature and two-stage processing under constant conditions. The most convenient operation resulted in a two-stage soaking process because of time, energy and cost savings, control convenience, product cooling anticipation and a reasonably high mass yield.

25 ref.; International audience; The drying of paddy rice may result in quality degradation, expressed as a head kernel yield, leading to significant commercial depreciation of the product. A mathematical model of the drying and of the quality degradation process was combined with a dynamic optimization algorithm to determine the drying conditions (air temperature and relative humidity as functions of time) that ensured the highest possible final product quality for a specified drying time and a specified final moisture content. The robustness of the optimal drying strategy with respect to the initial state of the product, to the model parameters and to the initialization of the optimization algorithm was verified. The compromise between the highest achievable final quality and the allowed total drying time was studied. The combination of simulation and optimization yielded a new insight in the rice drying process and in the quality preservation strategies.

International audience; Frying is one of the way for performing drying of food material that permits to obtain very short duration. However the control of such operation is difficult because of the immersion of product into hot oil bath that imply difficult or impossible sensors implementation. Such problems are encoutered for Dehydration Soaking Process (DISP). In the case of Batch drying using frying of food stuffs, an original approach is presented. An indirect measurement of moisture content is performed as a combination of easy to do oil bath temperature mesasurement and an estimator. Validation is provided and performance is well established. Because of the ability of moisture content real time measurements, a control strategy is studied and put into practice. An optimal predictive controller is proprosed, able to put into practice several kind of control objectives. Results are discussed and extension of the strategy is introduced

Aim The aim of this study is to investigate the effect of a broad spectrum of culture conditions on the acidification activity and viability of Carnobacterium maltaromaticum CNCM I-3298, the main technological properties that determine the shelf-life of biological time-temperature integrator (TTI) labels. Methods and results Cells were cultivated at different temperatures (20-37°C) and pH (6-9·5) according to a modified central composite design and harvested at increasing times up to 10 h of stationary phase. Acidification activity and viability of freeze-thawed concentrates were assessed in medium mimicking the biological label. Acidification activity was influenced by all three culture conditions, but pH and harvest time were the most influential. Viability was not significantly affected by the tested range of culture conditions. Conclusions Carnobacterium maltaromaticum CNCM I-3298 must be cultivated at 20°C, pH 6 and harvested at the beginning of stationary phase to exhibit fastest acidification activities. However, if slower acidification activities are pursued, the recommended culture conditions are 30°C, pH 9·5 and a harvest time between 4-6 h of stationary phase. Significance and impact of the study Quantifying the impact of fermentation temperature, pH and harvest time has led to a predictive model for the production of biological TTI covering a broad range of shelf-lives.

National audience

International audience

Communication orale sur invitation; International audience

International audience