The aim of this study was to evaluate the capacity of an electronic nose, the NeOse Pro, to assess the alteration of two food matrixes of animal origin, beef and salmon. For each matrix, two types of samples were analyzed, natural samples and simplified “diluted” samples based on meat juice and agar. Samples were inoculated with specific spoilage organisms and stored for 6 days at 8°C under different conditions: air, modified atmosphere packaging, and vacuum packaging. A non-inoculated control sample was stored at -80°C under vacuum packaging. Results of the NeOse Pro were compared with gas chromatography coupled to mass spectrophotometry analysis. For this purpose, heatmaps, principal component analysis and discriminant analysis were used. GC-MS results show that the major detected volatile organic compounds for beef stored under air are dimethyl disulfide and ethyl acetate. For salmon stored under air, it was mainly dimethyl disulfide, methyl thioacetate, acetoin and ethyl acetate that were produced. For beef and salmon NeOse Pro and GC-MS results are consistent; samples stored under air are separated from other samples.

This study intends to demonstrate that acid titration at low pH is very well adapted to the monitoring of pepsin activity. After a description of the underlying principles, this approach was used during in vitro gastric digestions of a model of complex food containing 15 wt% of whey proteins, according to both static (2 h at pH = 3, Infogest protocol) and dynamic pH conditions (from pH 6.3 down to 2 in 1 h). Pepsin activity was quantitatively assessed in all experiments through the calculation of degrees of hydrolysis (DH). Final values of 3.7 and 3.0% were obtained in static and dynamic pH conditions, respectively, and validated using an independent method. Results also show that about 92% of the peptides were detected at pH = 3, and 100% for pH <= 2.5. Overall, the proposed approach proved to be very worthy to study protein hydrolysis during in vitro gastric digestions. (C) 2017 Elsevier Ltd. All rights reserved.

This study evaluated the ability of dairy matrices, different in composition (with and without fat) and structure (liquid and gel), to enhance microorganisms survival through digestion. The viability of three dairy microorganisms Streptococcus thermophilus, Brevibacterium aurantiacum and Hafnia alvei was measured during in vitro and in vivo digestion. S. thermophilus was highly sensitive to gastric stress, and was not found in the duodenal compartment. B. auranticum was moderately sensitive to gastric stress but resistant to duodenal stress. H. alvei was highly resistant to both stresses. LIVE/DEAD confocal microscopy's images, probed the effect of low pH on microorganisms survival. However, in vivo analyses (16S rRNA gene metabarcoding) failed to confirm in vitro observations since tested microorganisms were not detected. Despite of the different evolutions during digestion on buffer capacity, lipolysis, and rheological characteristics, we did not observe any protective effect of the dairy matrices on microorganisms survival.

Within the active field of in vitro digestion in food research, the COST Action INFOGEST aimed to harmonize in vitro protocols simulating human digestion on the basis of physiologically inferred conditions. A harmonized static in vitro digestion (IVD) method was recently published as a primary output from this network. To validate this protocol, inter-laboratory trials were conducted within the INFOGEST network. A first study was performed using skim milk powder (SMP) as a model food and served to compare the different in-house digestion protocols used among the INFOGEST members. In a second inter-laboratory study applying the harmonized protocol, the degree of consistency in protein hydrolysis was investigated. Analysis of the hydrolyzed proteins, after the gastric and intestinal phases, showed that caseins were mainly hydrolyzed during the gastric phase, whereas β-lactoglobulin was, as previously shown, resistant to pepsin. Moreover, generation of free amino acids occurred mainly during the intestinal phase.The study also showed that a few critical steps were responsible for the remaining inter-laboratory variability. The largest deviations arose from the determination of pepsin activity. Therefore, this step was further clarified, harmonized, and implemented in a third inter-laboratory study.The present work gives an overview of all three inter-laboratory studies, showing that the IVD INFOGEST method has led to an increased consistency that enables a better comparability of in vitro digestion studies in the future.

A mixture of nine microorganisms (six bacteria and three yeasts) from the microflora of surface-ripened cheeses were subjected to in vitro digestive stress in a three-compartment "dynamic gastrointestinal digester" (DIDGI). We studied the microorganisms (i) grown separately in culture medium only (ii) grown separately in culture medium and then mixed, (iii) grown separately in culture medium and then included in a rennet gel and (iv) grown together in smear-ripened cheese. The yeasts Geotrichum candidum, Kluyveromyces lactis and Debaryomyces hansenii, were strongly resistant to the whole DIDGI process (with a drop in viable cell counts of less than < 1 log CFU mL(-1)) and there were no significant differences between lab cultures and cheese-grown cultures. Ripening bacteria such as Hafnia alvei survived gastric stress less well when grown in cheese (with no viable cells after 90 min of exposure of the cheese matrix, compared with 6 CFU mL(-1) in lab cultures). The ability of Corynebacterium casei and Staphylococcus equorum to withstand digestive stress was similar for cheese and pure culture conditions. When grow in a cheese matrix, Brevibacterium aurantiacum and Arthrobacter arilaitensis were clearly more sensitive to the overall digestive process than when grown in pure cultures. Lactococcus lactis displayed poorer survival in gastric and duodenal compartments when it had been grown in cheese. In vivo experiments in BALB/c mice agreed with the DIDGI experiments and confirmed the latter's reliability. (C) 2015 Published by Elsevier Ltd.

Understanding the mechanisms of infant formula disintegration in the infant gastrointestinal tract is a key step for developing new formulas with health benefits for the neonate. For ethical reasons, the access to in vivo data obtained on infants is limited. The use of animal models can be an alternative but these experiments are labour intensive, expensive and results obtained show high inter-individual variability, making their interpretation difficult. The aim of this work was to develop a simple in vitro dynamic gastrointestinal digestion system, for studying infant formula digestion, and to validate it by comparing the kinetics of proteolysis obtained in vitro with in vivo data collected from piglets. Results showed a good correlation between in vitro and in vivo data and confirmed the rapid hydrolysis of caseins in gastric conditions, whereas whey proteins appeared more resistant to digestion.

The best model for studying food digestion remains the Human himself. However, getting ethical agreement to perform such experiments on human is difficult. Developing in vitro digestion tools appears as a crucial step for monitoring the behaviour and the kinetics of hydrolysis of the food during the different phases of the digestion process. The objective of this work was to develop a simple and rather cheap dynamic digestion system enabling the study of the disintegration occurring in in the gastro-intestinal tract. The device consists in two compartments i.e. stomach and small intestine and is controlled by the STORM (STOmach Regulation and Monitoring) software. This digestion system simulates the GI physiological states as follows: i) flow of secretions and enzymes in physiological amounts (pepsin, lipase, bile, pancreatin), ii) appropriate pH (acidification curve in the stomach) and neutralization of the pH in the intestine, iii) mixing in each compartments, iv) physiological transit time for the gastric and intestinal step of digestion. The differents functions are monitored by the sofware and are saved all along the digestion process. Relevant physiological parameters are essential to simulate as close as possible the human GI tract. To achieve this aim, an exhaustive analysis of the data from the literature has been realized in order to adjust the parameters of the digestion model, and the key parameters such as gastric acidification curve, gastro-intestinal emptying rate and enzymes flow have been modelled as a function of the stage of life (infants vs adults). Validation of this model by a comparison of the kinetics of proteolysis of an infant formula observed either in an animal model (piglets) or in the in vitro model is currently under investigation. This model offers numerous advantages as compared to in vitro static models. Despite this, the model should be improved by (1) making the stirring conditions more physiologically relevant, (2) adding a dialysis membrane to mimic nutrients absorption in the intestinal compartment.

Portions of pressed, uncooked Saint-Nectaire cheese were packaged either under vacuum in low water-permeability film (LWP) or in air in film with medium gas and water permeabilities (MWP) or with high water permeability (HWP), then ripened for four weeks and evaluated for microbiological and biochemical properties and appearance. LWP totally eliminated cheese respiration and limited water loss. Consequently, the appearance of the cheese surface was totally modified: mycelia disappeared as a result of decreased yeasts, moulds and Gram + non-lactic acid bacteria, and the entire surface was covered with a red/orange smear. The two other films allowed significant respiratory activity without a decrease in moulds or yeasts. For cheese portions wrapped with HWP, mass loss, lactic acid consumption and proteolysis were the highest and although the appearance of the cheese surface did not change throughout the four weeks, considerable undesirable growth of the ripening flora was observed. (c) 2011 Elsevier Ltd. All rights reserved.

Dans le cadre de ses travaux dans le domaine des capteurs et de la mesure en ligne pour l’automatisation de la fabrication fromagère, l'unité de génie et microbiologie des procédés alimentaires de Thiverval Grignon a travaillé sur la coagulation et le raffermissement des caillés, le présent document présente une méthode de suivi de la synérèse. La synérèse est une étape importante de la fabrication fromagère. Le lait passe tout d’abord d’un état liquide à un état de gel appelé coagulum puis la synérèse démarre et transforme le coagulum en caillé. Le réseau protéique constituant le gel se contracte et expulse une fraction liquide, le lactosérum. La quantité de lactosérum rejeté et sa dynamique (vitesse de la synérèse) ont une influence sur le développement microbien lors de l’affinage. La synérèse peut affecter fortement la qualité finale du fromage. De nombreuses variables, liées au processus fromager, influencent la synérèse et plus globalement l’égouttage il s’agit essentiellement de la taille des particules de caillé, de la température et de la pression qui sera appliquée au moulage (Johnston et al., 1998 ; Whitehead et Harkness, 1954). La mesure de la taille des grains améliorerait le processus de fabrication fromagère. Guillemin et al., (2006), s’appuyant sur le brevet de Perret et al., (2002), ont développé un système de mesure en temps réel de cette taille basé sur une mesure optique et une mesure de contrainte. Cette dernière permet de tenir compte de l’agitation. Ce système simple et facile à mettre en œuvre s’est révélé insuffisant pour une application industrielle malgré l’utilisation de traitements avancés du signal optique : une seule mesure en un point ne donne pas la précision voulue. Une autre méthode a été développée, dans le même esprit de mesure en temps réel, mais en deux dimensions en utilisant une caméra ou un appareil photographique numérique, elle nécessite une bonne prise de vue et des traitements avancés des images obtenues. Le suivi de la taille des grains de caillé au cours du temps devrait permettre de stopper la synérèse à un instant opportun pour la qualité finale du fromage. Nous proposons une méthode de mesure sur des échantillons synthétiques pour valider le système et l'analyse des images.

An optical sensor formerly developed for the monitoring of milk coagulation was modified to allow online determination of casein particle size distribution and of the volume fraction relative to the whey as a function of time. Two methods were assessed to process the signals. The first one was based on the determination of a specific voltage threshold of the optical signal. The results were not satisfying. The second method used multiple thresholds of the optical signal associated with data processing using neural networks. For the considered experimental conditions, the casein particle volume fraction was estimated with a relative error of 23%, and the casein particle size distribution with 7.5% maximum relative error.

A technique that used multivariate data analysis to combine mid-infrared (MIR) spectroscopy with front-face fluorescence spectroscopy was used to discriminate between Emmental cheeses originating from different European countries: Austria (n=12), Finland (n=10), Germany (n=19), France (n=57), and Switzerland (n=65). In total, 163 Emmental cheeses produced in winter (n=91) and summer (n=72) periods were investigated. When Factorial Discriminant Analysis was applied to either the infrared or fluorescence spectral data the classifications were not satisfactory. Therefore, the first twenty principal components (PCs) of the PCA extracted from each data set (MIR and tryptophan fluorescence spectra) were pooled (concatenated) into a single matrix and analysed by Factorial Discriminant Analysis. Correct classifications were obtained for the samples for 89% of the calibration spectra and 76.7% of the validation spectra. The discrimination for cheeses from Finland was excellent, while Austrian, German, French and Swiss cheeses were also discriminated well although a few samples were misclassified. It was concluded that concatenation of the data from the two spectroscopic techniques is an efficient technique for authenticating Emmental cheeses independently of their manufacturing period.

276 vins de meme cepage, le Gamay, ont ete collectes durant 3 annees (1998, 1999, 2000) et analyses par spectroscopie moyen infrarouge a transmission afin d'authentifier les regions d'origine, Gaillac, Beaujolais ou Touraine. Les analyses spectroscopiques en transmission sont realisees sur des membranes en polyethylene sur lesquelles 75 μL de vin melanges avec le meme volume d'acetone sont deposes et seches sous vide au dessiccateur. Les donnees spectrales, comprises entre 800 cm-1 et 1800 cm-1, sont traitees par trois methodes de classification: a) classement par la methode du plus proche voisin (PPV); b) selection pas a pas des nombres d'onde les plus significatifs associee a une analyse factorielle discriminante avec validation croisee (AFD); c) regression par les moindres carres partiels (PLS). La premiere methode (PPV) donne des resultats peu satisfaisants; 65% seulement des echantillons de validation sont correctement classes dans leur groupe d'origine. Par AFD et par PLS, les taux d'echantillon bien classes sont de 90% et de 85% respectivement.