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International audience; This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

International audience; This article critically reviews the current state of knowledge on the quality of animal-source foods according to animal production and food processing conditions, including consumer expectations-behaviours and the effects of consumption of animal-source foods on human health. Quality has been defined through seven core attributes: safety, commercial, sensory, nutritional, technological, convenience, and image. Image covers ethical, cultural and environmental dimensions associated with the origin of the food and the way it is produced and processed. This framework enabled to highlight the priorities given to the different quality attributes. It also helped to identify potential antagonisms and synergies among quality attributes, between production and processing stages, and among stakeholders. Primacy is essentially given to commercial quality attributes, especially for standard commodity animal-source foods. This primacy has strongly influenced genetic selection and farming practices in all livestock commodity chains and enabled substantial quantitative gains, although at the expense of other quality traits. Focal issues are the destructuration of chicken muscle that compromises sensory, nutritional and image quality attributes, and the fate of males in the egg and dairy sectors, which have heavily specialised their animals. Quality can be gained but can also be lost throughout the farm-to-fork continuum. Our review highlights critical factors and periods throughout animal production and food processing routes, such as on-farm practices, notably animal feeding, preslaughter and slaughter phases, food processing techniques, and food formulation. It also reveals on-farm and processing factors that create antagonisms among quality attributes, such as the castration of male pigs, the substitution of marine-source feed by plant-based feed in fish, and the use of sodium nitrite in meat processing. These antagonisms require scientific data to identify trade-offs among quality attributes and/or solutions to help overcome these tensions. However, there are also food products that value synergies between quality attributes and between production and processing phases, particularly Geographical Indications, such as for cheese and dry-cured ham. Human epidemiological studies have found associations between consumption of animal-source foods and increased or decreased risk for chronic non-communicable diseases. These associations have informed public health recommendations. However, they have not yet considered animal production and food processing conditions. A concerted and collaborative effort is needed from scientists working in animal science, food process engineering, consumer science, human nutrition and epidemiology in order to address this research gap. Avenues for research and main options for policy action are discussed

Escherichia coli O157:H7 is responsible for foodborne poisoning, incriminating contaminated animal food and especially beef meat. This species can survive in the digestive tract, but, up to now, very few studies have considered its survival during the gastrointestinal digestion of meat. The present study aimed to investigate the survival of the pathogenic strain E. coli O157:H7 CM454 during the gastrointestinal digestion of ground beef meat and its interactions with meal components using a semidynamic digestive model. The CM454 strain in meat survived throughout digestion despite acidic pH (pH 2) and the presence of bile salts. The addition of nitrite and ascorbate in the digestion medium led to a decrease in strain survival. During digestion, a release of free iron was observed, which was accentuated in the presence of the CM454 strain. In addition, the strain modified the Fe2+/Fe3+ ratio, in favor of Fe2+ compared to the noninoculated meat sample. In the presence of nitrite, nitroso compounds such as nitrosamines, nitrosothiols, and nitrosylheme were formed. E. coli O157:H7 CM454 had no impact on N-nitrosation but seemed to decrease S-nitrosation and nitrosylation.

International audience; Food-derived bioactive peptides have generated an increasing interest in the field of health and well-being research. They can act either against the metabolic syndrome, participate in regulating the oxidation balance or act on the immune system. The aim of this study is to develop a workflow to generate bioactive peptides from three porcine offals namely, heart, liver, and lung and one muscle the Longissimus Dorsi, by combining in silico and in vitro approaches. Bioinformatics tools (e.i. BIOPEP and Uniprot) permitted to orientate the choice of enzymes for generating abundant bioactive peptides from the four studied porcine products. With papain and subtilisin, the main bioactivities potentially released were ACE inhibitors, DPP4 inhibitors and antioxidant peptides. An in vitro validation study using papain and subtilisin demonstrated high DPP4 inhibitors and antioxidant bioactivities for the generation of peptides. This work allowed: i) the identification of all proteins that composed porcine heart, liver, lung and LD muscle that could be useful for the scientific community, ii) the development of a workflow to select most abundant proteins in a product while considering abundance factors and iii) the potential of porcine meat and offals to generate DPP4 inhibitors and antioxidant peptides. However, there is still a need in developing new tools in order to face limitations of mass spectrometry for the identification of peptides with less than six amino acids. Such a work may contribute to the development of the circular economy and the innovative creation of value-added products from animal production.

International audience; PSE-like muscle defect is of great importance in the cooked ham industry because of the economic losses it can cause. Although this muscle defect has been widely studied from a mechanistic angle, there is a lack of reliable and practical markers. This study proposes the use of chemometrics for the spectral fingerprinting of pig plasma to predict the PSE-like muscle defect in cooked hams. Both MALDI-TOF mass spectrometry and ATR-FTIR spectroscopy were used to obtain protein and chemical function fingerprints. Though the two approaches showed very good predictive capacity, MALDI-TOF mass spectrometry was found to be better suited to predicting normal hams, i.e. hams without the defect; while ATR-FTIR spectroscopy was found to be better suited to predicting the PSE-like muscle defect. These results demonstrated the feasibility of predicting the PSE-like defect using spectral fingerprinting and chemometrics approaches.

International audience; Preparing a food bolus for swallowing is the first and major goal of oral processing ensured by mastication. To fulfill this goal, mastication is accurrately adjusted to the structure and texture of the food. Since the bolus is the main outcome of food oral processing, there is growing interest in improving understanding the food bolus and its features at the end of the masticatory sequence and throughout its formation. Although this step is trivial, its execution is somewhat more complex than it appears. Until now, the food bolus produced has not subjected to full analysis, mainly due to the lack of accessibility during in vivo oral processing. To overcome this difficulty, we developed a masticator apparatus, named AM2, on the basis of in vivo compression and shear stresses applied on food during oral processing. The apparatus was validated against particle size analyses of boluses produced by individuals presenting normal mastication. The present paper provides a comprehensive overview of the various potential uses of the AM2 apparatus to produce food boluses for a large range of scientific needs. The food bolus contains much valuable information regarding the progress of mastication, the completion of the function and its role in food disruption, the oral release of food compounds, changes and bioaccessibility, and finally its impact on nutrition. The AM2 apparatus can also be used to simulate mastication in specific populations, such as the elderly and children, and to address various objectives related to this initial step of digestion.

International audience; PSE-like technological defect in the meat industry is of great importance due, to the economic loss it can cause. It has been studied from the biochemical perspective but very few studies have focused on tissular characterization. This study proposes innovative approaches that combine mechanistic elucidation and the discovery of potential biomarkers. This study focused on muscle destructuration using imaging and label-free quantitation. Oxidative stress and apoptotic processes were found to be linked to the specific evolution of the PSE-like destructuration zone, namely ‘inner’, within hams. Four m/z values were found to be related to the specific localization of the PSE-like defect, and a mass shift of 27 Da suggested a possible connection with oxidation. These potential markers of the PSE-like area in ham provide a new perspective to sort raw material based on the possible development of PSE-like areas.

International audience; The International Agency for Research on Cancer recently classified cured meats as carcinogenic for humans and red meats as probably carcinogenic. Mutagens can be formed during meat process or digestion. In a previous study, we used a dynamic artificial digestive system (DIDGI®) to investigate protein oxidation and N-nitrosation during bovine meat digestion. This new paper completes the previous one by focusing on the endogenous heme iron nitrosylation. Low nitrosylation due to nitrate initially present in meat and to ammonia oxidation in the stomach was observed in the digestive tract even in conditions in which no nitrite was added to the model. The endogenous addition of nitrite (1 mM) considerably increased heme iron nitrosylation while a significant decrease was observed with prior meat cooking (30 min at 60 and 90 °C).

International audience; Livestock generates high quantities of residues, which has become a major socioeconomic issue for the meat industry. This review focuses on the identification of bioactive peptides (BPs) in animal byproducts and meat wastes. Firstly, the main bioactivities that peptides can have will be described and the methods for their evaluation will be discussed. Secondly, the various origins of these BPs will be studied. Then, the techniques and tools for the generation of BPs will be detailed in order to discuss, in the final part, how peptides could be used and assimilated. BPs possess diverse biological activities and can be strategic candidates for substituting synthetic molecules. In silico potentiality studies are a helpful tool to understand and predict BPs released from proteins and their potential activities. However, in vitro validation is often required. Although BP use is compelled by strict regulations in relation to the field of application, they are also limited by their low bioavailability and bioaccessibility. Therefore, it is important to test peptide stability during gastrointestinal digestion. Protective strategies have been discussed since their use could improve the stability and effectiveness of BPs.

Introduction et but de l’etude Le vieillissement peut s’accompagner d’une baisse du flux salivaire et du nombre de dents entrainant une moindre consommation de viande avec un risque de denutrition et de fonte musculaire. Ainsi, pour augmenter la consommation de proteines chez les seniors, il est important de proposer des aliments carnes adaptes a leurs capacites orales. Dans ce contexte, le but de ce travail est d’objectiver le confort en bouche lors de la prise d’aliments developpes specifiquement chez deux populations seniors a l’etat buccodentaire contraste. Materiel et methodes Deux groupes de sujets (> 65 ans et vivant a domicile), 36 (18H, 18F) presentant une bonne dentition (BD, âge = 73 ± 5, UFP (unites fonctionnelles posterieures)= 8 ± 1) et 36 (15H, 21F) une mauvaise dentition (MD, âge = 74 ± 5, UFP = 3 ± 1) ont ete choisis. Les deux groupes sont sans risque de denutrition (MNA = 27,4 ± 0,3). Ils ont un flux salivaire stimule (FSS) non different entre BD et MD et de moyenne globale 1,8 ± 0,7 mL/min. Deux matrices, bœuf (Bo) et poulet (Po), elaborees selon un meme procede, ont ete evaluees (bouchee de 6 g) deux fois au moyen d’un questionnaire sensoriel divise en 5 parties [1] , [2] : confort en bouche et facilite a manger, facilite a former un bol, douleurs ressenties, texture et flaveur. Les donnees ont ete traitees par ANCOVA (2 facteurs categoriels [(Bo, Po) et (BD, MD)] + 1 facteur continu [FSS]). Resultats et analyse statistique Exprimes sur une echelle de 0 a 100, les resultats montrent que les sujets MD jugent les 2 matrices plus confortables en bouche que les sujets BD (75 ± 1,8 et 71 ± 1,8, F = 6,1, p La comparaison entre les matrices souligne que Po est juge plus confortable que Bo (77 ± 1,8 et 68 ± 1,8, F = 10,7, p Il n’y a pas d’effet significatif du FSS sur l’evaluation du confort. Conclusion Le resultat remarquable de cette etude est que les sujets avec un mauvais etat bucco-dentaire jugent les produits plus confortables et plus faciles a manger que les sujets normo-dentes. Globalement, les procedes de fabrication permettent d’obtenir deux viandes confortables en bouche, la matrice de poulet etant jugee encore plus confortable que celle de bœuf. La suite de ce travail portera sur les caracteristiques structurales et biochimiques du bol alimentaire forme par la mastication pour ces deux groupes de seniors et sur leur lien avec la perception du confort et la digestibilite des deux matrices carnees.

International audience; The gelatin used for the hard capsules manufacturing must meet strict dissolution specification to ensure the delivery of drugs at right time in the digestive tract. However, the environment of production and storage time affect the quality of gelatin dissolution. This study aimed to identify the mechanisms underlying the geographical environment of production and aging impact on the gelatin dissolution rate. Gelatins from 3 different origins of production (A, B & C), whose dissolution rate had been previously characterized, were analyzed by Raman microspectroscopy before and after aging. The principal component analysis (PCA) clearly separated the aged gelatins from non-aged ones. The spectra interpretation suggested the denaturation of gelatin triple-helices. In addition, the formation of cross-links such as dityrosine, glucosyl-galactosylhydroxylysinonorleucine and proteoglycan-like sugar adducts was strongly suspected. Whatever the gelatin aging state, PCA systematically separated the B-gelatins from A and C-gelatins. Pentosidine cross-link was likely to vary depending on the production origin. Finally, the quality of dissolution was discriminated for aged gelatins of A-origin: the non-compliant gelatins exhibited higher lipid content than the compliant ones.

International audience; Fruit and vegetables (F&V) polyphenols have numerous positive health effects, ascribed either to their antioxidant activity within the gastrointestinal tract (GIT) or to bioactivity of their absorbed metabolites. The effect of the F&V matrix on the gastrointestinal bioaccessibility of polyphenols was investigated along with its possible interaction with protein digestion. Minipigs were fed a complete meal with either cubed F&V (apple, plum, artichoke) added, or the corresponding phenolic extract (PE). Gastric and ileal chymes were kinetically collected over the postprandial period. The overall polyphenol bioaccessibility in the stomach was found to be 1.5% and 3.1% after F&V and PE consumption, respectively. The lower release rate from artichoke than from apple showed evidence of a plant effect. Flavanol monomers and glucoside conjugates were not recovered in the ileum in agreement with their absorption in the upper GIT. Interestingly, PE, but not F&V, significantly decreased the speed and efficiency of dietary protein digestion.

In the elderly, masticatory function often presents failure in certain oral tasks due to impairment such as decline in muscular force, jaw or tongue motility, neuro-muscular coordination, tooth damage, malocclusion and saliva production. Great disparity is observed in the various and potentially cumulative oral declines that occur with ageing. Such difficulties may have an impact on food consumption and nutritional status. To obtain better understanding of the consequences of several oral deficiencies, a series of swallowable boluses were prepared in vitro with the AM2 masticator apparatus with normal and deficient programming. Physiological normal mastication (NM) was simulated using in vivo data from healthy subjects. Chewing deficiencies were reproduced by alteration of NM programming to perform different levels and combinations of force loss, lack of saliva and decrease in the motility of oral elements. Poultry meatballs were used as test-food. Particle size distribution in the food bolus was measured by sieving and rheological features (hardness, cohesiveness and elasticity) were assessed with a TPA test. Compared to the NM outcome, significant and gradual deterioration of the food bolus was observed and associated with alteration in force, saliva and motility. Combinations of several failures led to greater or cumulative deficiencies in swallowable bolus properties. For the elderly presenting a high prevalence of various oral injuries, tailoring textured food cannot be ignored as a solution for remedying deficiencies and favoring the formation of a safe-swallowable bolus, which is an essential vector of nutrients. Knowing the impacts of oral injuries on the food bolus is obviously a requisite for developing diet strategies, including nutritional items for specific populations.

International audience; Chemical changes that occur during the storage and processing of food can affect its nutritional content. During digestion, the exposure of food to considerable variations of pH and high oxygen and peroxide concentrations also participates in the deterioration of nutrients, with a negative impact on the nutritional value of the diet and harmful consequences for human health. Iron plays a key role in gastrointestinal chemistry. Haem iron, which exists only in meat, and non-haem iron, present in most foods, are catalysts of most of the reactions implicated in the deterioration of nutrients. Disintegration of food matrix due to mechanical forces and enzymatic hydrolysis favour this endogenous process. This paper provides a review of what is known in the literature concerning the mechanisms and kinetics of endogenous reactions catalysed by iron. The main consequences on nutrient bioavailability are reported and protective strategies against the deleterious effect of iron are discussed.

• Protein interactions play a key role in determining the final structure and properties of products.

International audience; BACKGROUNDSynchrotron radiation circular dichroism (SRCD) and Fourier transform infrared (FTIR) spectroscopy were used to examine the conformation evolution of micellar casein (MC) powder during storage and to determine whether the spectral changes could be related to their solubility evolution. RESULTSA loss in intensity of SRCD spectra as a function of storage time has been observed. Quantification of secondary structures revealed losses of -helix content during storage. Moreover, a redshift of the amide I band in the FTIR spectrum was demonstrated during the storage and was interpreted as a rearrangement of the secondary structure of the protein, which is in line with the SRCD results. The qualitative results obtained by FTIR clearly support the quantitative evolution of the secondary structure obtained by the analysis of SRCD spectra. Principal component analysis (PCA) of FTIR spectra permits a good separation of samples according to the storage time. PCA shows that the evolution of secondary structures and solubility loss are closely linked. CONCLUSIONWith the quantitative data provided by SRCD spectra, it was established that, whatever the storage conditions, a unique curve exists between loss of -helix content and loss in solubility, showing that loss of -helix content is a marker of solubility loss for the MC powders studied. (c) 2017 Society of Chemical Industry

International audience; Gelatin is a biopolymer produced worldwide through its dissolution rate is variable. During the manufacturing process, gelatin is exposed to high temperatures known to be responsible for cross-link formation. Moreover, bleaching agents such as hydrogen peroxide are added to lighten the gelatin, leading to oxidation reactions that form cross-links. Cross-links have been reported in the literature to be formed between amino acids and related to decreased gelatin dissolution. The variability of gelatin dissolution is important since gelatin is used in the pharmaceutical industry to make hard capsules which have to satisfy strict dissolution specifications. The objective of this study was to determine how the oxidative potential of gelatin may explain the variability of its dissolution. Amino acid composition was assessed by HPLC and gelatin chemical composition was studied with HRMAS-NMR. Iron and aldehyde contents were also measured. Cross-links involving aldehyde functions were strongly suspected to be formed with aging, as were desmosine-like and dityrosine cross-links. All these cross-links were formed during oxidation reactions that are also strongly suspected to occur during aging. In addition, the origin of production affects the oxidative potential of gelatins when considering their iron content. The amount of aldehyde functions, which reflects the oxidation state of gelatins, differed as a function of their origin of production. The dissolution rate of gelatins could be linked to their oxidative potential (iron content) and the aldehydic products of lipid oxidation. Interestingly, the causes for differences in dissolution varied as a function of their origin of production.

International audience; Background: Meat cooking conditions in in vitro and in vivo models have been shown to influence the rate of protein digestion, which is known to affect postprandial protein metabolism in the elderly.Objective: The present study was conducted to demonstrate the effect of cooking conditions on meat protein assimilation in the elderly. We used a single-meal protocol to assess the meat protein absorption rate and estimate postprandial meat protein utilization in elderly subjects.Design: The study recruited 10 elderly volunteers aged 70–82 y. Each received, on 2 separate occasions, a test meal exclusively composed of intrinsically 15N-labeled bovine meat (30 g protein), cooked at 55°C for 5 min [rare meat (RM)] or at 90°C for 30 min [fully cooked meat (FCM)], and minced. Whole-body fluxes of leucine, before and after the meal, were determined with the use of a [1-13C]leucine intravenous infusion. Meat protein absorption was recorded with the use of 15N enrichment of amino acids.Results: Postprandial time course observations showed a lower concentration in the plasma of indispensable amino acids (P < 0.01), a lower entry rate of meat leucine in the plasma (P < 0.01), and a lower contribution of meat nitrogen to plasma amino acid nitrogen (P < 0.001), evidencing lower peripheral bioavailability of meat amino acids with RM than with FCM. This was associated with decreased postprandial whole-body protein synthesis with RM than with FCM (40% compared with 56% of leucine intake, respectively; P < 0.01).Conclusions: Whereas meat cooking conditions have little effect on postprandial protein utilization in young adults, the present work showed that the bioavailability and assimilation of meat amino acids in the elderly is lower when meat is poorly cooked. In view to preventing sarcopenia, elderly subjects should be advised to favor the consumption of well-cooked meat. This trial was registered at clinicaltrials.gov as NCT02157805.

Fresh red meat and cured meat consumption increases the risk of gastro-intestinal cancers and it is strongly suspected that nitrosylheme is implicated by stimulating the endogenous production of mutagenic aldehydes and N-nitroso compounds. To investigate the extent of endogenous heme iron nitrosylation an experimental in vitro model that mimics the physicochemical conditions of the gastro-intestinal tract was used in association with a mathematical model of chemical reaction kinetics. The combined effect of pH (from 7.2 to 3.2) and myoglobin oxidation state was evaluated in the reaction of nitrite with heme iron, and the observed rate constants of the reactions were determined. Nitrosylation was optimal under mildly acidic conditions (pH 6.5-4.7). Up to 20% of myoglobin can be nitrosylated under gastro-intestinal conditions in this pH range. The effect of various antioxidants (from meat or vegetables) on the endogenous nitrosylation process was also tested.

Gelatin is used to make hard capsules and has to meet strict dissolution specifications to guarantee homogeneous drug delivery. The aging of gelatin induces a decrease of its dissolution rate due to the formation of intra- and intermolecular cross-links. Cross-link formation has shown to be dependent on the environmental conditions of production, such as temperature and humidity, and therefore on the geographic origin of production. Gelatin structure consists of an amorphous phase (coil structure) and a crystal phase (triple-helixes) and is very sensitive to environmental changes. The present work aims at understanding the role and effects of structural changes during aging on gelatin dissolution, taking into account the origin of production. The molecular structure of pig skin gelatins from three different production sites of the same company were studied by differential scanning calorimetry, synchrotron circular dichroism and 1H nuclear magnetic resonance. It turned out that aging induced the melting of triple-helixes, an increase of random coils and, probably, β-turn conformations. The gelatin structure varied with the origin of production and thus affected the dissolution rate. Gelatins with non-compliant dissolution rates exhibited a higher amount of amorphous phase after aging than compliant gelatins. Although it was not possible to formulate any certain interpretation of the synchrotron circular dichroism results regarding gelatin dissolution, this technique is able to differentiate compliant dissolutions from non-compliant ones, even before gelatin aging.

The reaction of nitrite with different amino acids containing secondary amino groups was tested under simulated in-vitro conditions of the digestive tract. After treatment, tryptophan was the only amino acid that exhibited specific UV absorbance of nitrosamines at 335 nm, supporting the assumption that it is the main source of endogenous nitrosamines. The combined effect of pH (from 2 to 6.5) and nitrite (from 0.1 to 20 mM) was analyzed and the mechanisms and kinetic laws of tryptophan N-nitrosation were determined. The model was then completed by the addition of iron and various antioxidants in concentrations reflecting different diets. The results clearly demonstrated that, in the presence of iron, large amounts of N-nitroso-tryptophan can be formed even at neutral pH, as in the intestine. Antioxidants (ascorbic acid, trolox C, β carotene, chlorogenic acid, phytic acid and butylated-hydroxytoluene) had various impacts on the extent of N-nitrosation, depending on the iron level.

International audience; The pharmaceutical industry requires narrow variability in the dissolution rate of hard gelatin capsules. To test this property, gelatin is aged in high temperature and humidity conditions to mimic gelatin shelf-life. These conditions induce cross-link formation in gelatin chains and change the properties of the capsule. Gelatin is produced worldwide in various environmental conditions. This study set out to evaluate the impact of geographic production origin on gelatin composition, before and after aging treatment, and on its dissolution properties. Non-aged and aged pig skin gelatins from three different production plants (A, B and C) were analyzed in raw granules and in powder by near infrared and fluorescence spectroscopy to identify the mechanisms of cross-link formation during aging. Gelatin composition (lipids, dityrosine, 3,4 dihydroxyphenylalanine (DOPA)) and oxidation level, before and after aging, varied according to production origin. The gelatin from C showed no variability in dissolution rate, while gelatins from A and B dissolved more slowly after aging. Near infrared spectroscopy results suggest that water was more strongly bound to the gelatin chains in the gelatins that yielded non-compliant dissolution test results. Non-compliant gelatin exhibited more CH2, usually assigned to lipids, and more aldehydes. Even before aging we found that non-compliant gelatins tended to fluoresce more at 344 nm under 280 nm excitation. These results open new perspectives for designing tools to predict the dissolution quality of freshly produced gelatins.

International audience; We aimed to identify and quantify the peptides generated during in vitro digestion of cooked meat by liquid chromatography coupled with high resolution mass spectrometer. A total of 940 non-redundant peptides in the gastric compartment and 989 non-redundant peptides in the intestinal compartment were quantified and identified. Among the 71 different proteins identified, 43 meat proteins were found in the two digestive compartments, 20 proteins were specific to the gastric compartment and 8 proteins to the intestinal compartment. In terms of estimation, the proteins involved in muscle contraction and structure were preferentially enzymatically hydrolyzed in the small intestine. The effect of cooking provided different but less clear patterns of digestion. To the best of our knowledge, this constitutes the highest number of peptides identified in beef meat digests and provides a comprehensive database for meat protein digestion associated with cooking conditions. Such quantitative and qualitative differences may have important nutritional consequences.

The production of oxygen free radicals catalysed by non-haem iron was investigated in an in vitro mimetic model of the digestive tract using specific chemical traps. Superoxide radicals (O2(∗-)) and their protonated form (hydroperoxyl radicals, HO2(∗)) were detected by the reduction of nitroblue tetrazolium into formazan, and hydroxyl radicals (OH(∗)) were detected by the hydroxylation of terephthalate. Under gastric conditions, O2(∗-)/HO2(∗) were detected in higher quantity than OH(∗). Increasing the pH from 3.5 to 6.5 poorly affected the kinetics of free radical production. The oxidations generated by these free radicals were estimated on myofibrils prepared from pork rectus femoris muscle. Myofibrillar lipid and protein oxidation increased with time and oxidant concentration, with a negative impact on the digestibility of myofibrillar proteins. Plant food antioxidants considerably decreased free radical production and lipid oxidation but not protein oxidation.

International audience; Hydroxyalkenals are lipid oxidation end-products resulting from the oxidation of polyunsaturated fatty acids (PUFA). This study aimed at quantifying the production of 4-hydroxy-2-nonenal-protein adducts (HNE-P) via Michael addition from n-6 PUFA oxidation in the gastric digesta of mini-pigs after the consumption of meat-based meals with different plant antioxidant contents. Using the accuracy profile procedure, we validated an extraction protocol for the quantification of HNE-P by GC-MS/MS in gastric contents. The formation of HNE-P in the gastric compartment was observed for the first time, with concentrations ranging from less than 0.52 to 1.33 nmol HNE-P per 500 mg digesta. Nevertheless, most gastric HNE-P levels were below the limit of quantification of 0.52 nmol HNE-P per 500 mg digesta. In this animal study, the protective effect of plant antioxidant sources on HNE-P formation was not evidenced contrasting with the results using TBARS as markers.

Background: Meat protein digestibility can be impaired because of indigestible protein aggregates that form during cooking. When the aggregates are subsequently fermented by microbiota, they can generate potentially harmful compounds for the colonic mucosa. Objective: This study aimed to evaluate the quantity of bovine meat protein escaping digestion in the human small intestine and the metabolic fate of exogenous nitrogen, depending on cooking processes. Methods: Sixteen volunteers (5 women and 11 men; aged 28 6 8 y) were equipped with a double lumen intestinal tube positioned at the ileal level. They received a test meal exclusively composed of 120 g of intrinsically 15 N-labeled bovine meat, cooked either at 55C for 5 min (n =8 ) or at 90C for 30 min (n = 8). Ileal effluents and blood and urine samples were collected over an 8-h period after the meal ingestion, and 15 N enrichments were measured to assess the digestibility of meat proteins and the transfer of dietary nitrogen into the metabolic pools. Results: Proteins tended to be less digestible for the meat cooked at 90C for 30 min than at 55C for 5 min (90.1% 6 2.1% vs. 94.1% 6 0.7% of ingested N; P = 0.08). However, the particle number and size in ileal digesta did not differ between groups. The appearance of variable amounts of intact fibers was observed by microscopy. The kinetics of 15 N appearance in plasma proteins, amino acids, and urea were similar between groups. The amount of exogenous nitrogen lost through deamination did not differ between groups (21.2% 6 0.8% of ingested N). Conclusions: Cooking bovine meat at a high temperature for a long time can moderately decrease protein digestibility compared with cooking at a lower temperature for a short time and does not affect postprandial exogenous protein metabolism in young adults. The study was registered at www.clinicaltrials.gov as NCT01685307. JN utrdoi: 10.3945/jn.115.216838.

International audience; Digestibility of myofibrillar proteins by pepsin was determined by in vitro trials and mathematical modelling. A primary model was developed to predict in vitro digestion kinetics, and a secondary model based on the mechanisms of protein denaturation was then added to take into account the effect of meat heating. Model predictions agreed with measurements in the pH and pepsin concentration ranges 1.8-3.8 and 6-50 U mg(-1) respectively. The utility of the model is illustrated by a simple example where meat is assumed to be heated homogeneously, and myofibrillar proteins to be directly in contact with pepsin. The combined effects of heating time, temperature, enzyme concentration and pH modified the digestibility value, which also depends on residence time in the stomach.

International audience; Gelatin obtained from pig skin constitutes about 50% of world production and is mainly composed of collagen extracted from skin by acidic baths and thermal treatments. The gelatin is used to make various products, notably hard gelatin capsules (HGC) which of varying solubility in water. This issue has been known for many years and has been, and remains, a subject of study and debate. The main reason for low gelatin dissolution rates is its tendency to form cross-links in the denatured collagen chains under specific conditions which stabilize the gel network and prevent dissolution. As it is extracted from animal tissues, gelatin may contain molecules other than collagen (sugars, lipids and other proteins) which may react with collagen chains to form covalent bonds. Although this biopolymer has been the subject of numerous publications, its structure and composition is not well defined. Indeed, there are many differences from an article to another. Consequently, the causes of HGC dissolution are not well identified and controlled.

The use of proteomics in the field of meat science has gained in robustness and accuracy. This is consistent with the genomic and bioinformatic tools. Its application to sensorial and technological meat quality traits is discussed as well as the emergence of sanitary and nutritional issue which will grow in a next future.

International audience; Previous studies indicate that the ingestion of oxidized vegetable oils leads to the incorporation of chemically reastive molecules issed from the decomposition of the initial lipid hydroperoxides into lipoproteins. The aim of the present study is to investigate the oxidation of dietary lipids in the gastric compartment and their inhibition by plant polyphenols provided either as fruit and vegetables (F&V) or an extract. Six minipigs received a standard Western diet containing primarily sunflower oil, ground beef meat, and starch. Polyphenols in different matrix forms were ingested either as cubed F&L or as the corresponding hydroacetonic extract. Sampling of the gastric digesta allowed the kinetic investigation of pH, heme and non-heme iron forms, total lipids, lipid-derived conjugated dienes (CD) and TBARS. F&V and the corresponding polyphenol extract delayed the gastric digestion process as shown for total lipid and heme iron contents. This study also demonstrated the occurence of in vivo oxidation of dietary lipids in the presence of meat iron. Interestingly, F&V played a protective role by totally inhibiting the accumulation of CD while largely decreasing the formation of TBARS. The polyphenol extract similarly slowed down the TBARS formation although it had no effect on the CD accumulation.

International audience; Meat is an appropriate source of proteins and minerals for human nutrition. Technological treatments modify the physical-chemical properties of proteins, making them liable to decrease the nutritional potential of meat. To counteract this damage, antioxidants and chaperone proteins in muscle cells can prevent oxidation, restore the function of denatured proteins, and thus prevent aggregation. This study aimed to explore the impact of indoor vs outdoor-reared meat protein composition on digestion and to associate protein markers to in vitro digestion parameters. Indoor-reared meat tended to show less oxidation and denaturation than outdoor-reared meat and was characterised by an overexpression of contractile and chaperone proteins. Outdoor-reared meat showed amplification of antioxidant and detoxification metabolism defending against oxidised compounds. Impacts on digestion remained minor. Several protein markers of in vitro digestion parameters were found for aged and cooked meat, linked to the detoxification process and to muscle contraction.

International audience; The present study aimed to evaluate the digestion rate and nutritional quality of pig muscle proteins in relation to different meat processes (aging, mincing, and cooking). Under our experimental conditions, aging and mincing had little impact on protein digestion. Heat treatments had different temperature-dependent effects on the meat protein digestion rate and degradation potential. At 70 °C, the proteins underwent denaturation that enhanced the speed of pepsin digestion by increasing enzyme accessibility to protein cleavage sites. Above 100 °C, oxidation-related protein aggregation slowed pepsin digestion but improved meat protein overall digestibility. The digestion parameters defined here open new insights on the dynamics governing the in vitro digestion of meat protein. However, the effect of cooking temperature on protein digestion observed in vitro needs to be confirmed in vivo.

The aim of the present study, the third in a series of three papers, is to show the effects of PRKAG3 and CAST gene polymorphisms on the quality traits of the Slovenian dry-cured ham “ Kraski prsut ” and their interaction with ham producers. Significant interaction of polymorphisms with producer in the case of salt content, lipid oxidation ( PRKAG3 Ile199Val ), proteolysis index ( CAST Arg249Lys ) and pastiness ( CAST Ser638Arg ) indicated that genotype manifestation was reliant on the manufacturing practice. PRKAG3 Ile199Val polymorphism affected several physico-chemical, rheological and sensory traits. The Ile/Ile genotype yielded less salty and softer hams, indicating beneficial effects on dry-cured ham quality. The effect of CAST polymorphisms was less pronounced, although the observed associations with pastiness, proteolysis index and several free amino acid concentrations indicate its possible influence on proteolysis, with haplotype CAST 249Arg/638Ser being associated with a higher degree of proteolysis.

The nutritional value of proteins was investigated after the storage and cooking of rhea M. Gastrocnemius pars interna. Oxidation of basic and aromatic amino acids, surface hydrophobicity and aggregation state of proteins, were determined in raw and cooked meat. In addition, myofibrillar proteins were exposed in vitro to proteases of the digestive tract. Cooking markedly affected the protein surface hydrophobicity. The BBP bound content was three times greater in cooked than in fresh rhea meat. A small increment in tryptophan content after cooking was observed. Storage influenced Schiff bases formation indicating the presence of protein-aldehyde adducts after cooking. High content of Schiff bases was found after cooking of samples stored for 5 days, demonstrating a probable implication of free amino groups, most likely from lysine. Cooking decreased the myofibrillar protein susceptibility to pepsin activity. After cooking, the proteolysis rate by pancreatic enzymes increased. Our findings support the importance of protein aggregation in the nutritional value of meat proteins.

Association between polymorphisms on PRKAG3 (Ile199Val) and CAST (Lys249Arg and Ser638Arg) genes and dry ham seasoning losses was studied. A total of 724 green hams (same pig crossbreed, same pig producer) were selected, genotyped (PCR-RFLP) and processed according to the rules of consortium for dry-cured ham Kraški pršut. Weight losses after each processing phase were recorded. We observed significant effect of interaction between gene polymorphism and dry ham producer on seasoning losses, indicating that the effect of studied genes differ in relation to manufacturing practice or product type, despite narrow consortium constraints. The analysis was thus made separately for each producer; in case of producer B, PRKAG3 affected salting, resting and overall losses (Val/Val higher than Ile/Ile or Ile/Val) but in case of producer A, the effect of PRKAG3 was significant only for salting losses (Ile/Val lower than Ile/Ile or Val/Val). Effects of CAST polymorphisms were significant only in case of producer A; CAST249 Arg/Arg hams showed the highest first salting, drying, and overall seasoning losses, whereas CAST638 Arg/Arg hams had the highest drying, ripening, and overall seasoning losses. In conclusion, PRKAG3 and CAST polymorphisms were associated with seasoning losses, important from economic viewpoint, but also for salt intake and product quality.

This study used complementary multi-scale analytical methods in order to better understand how technological procedures such as freezing and heating affect protein aggregation. The research was conducted on fresh and frozen Longissimus dorsi (LD) which were heated at different temperatures and for various times. Protein aggregates were measured using light scattering, SDS PAGE electrophoresis, and optical and scanning electron microscopy. Heating led to a higher molecular weight of aggregates, while freezing had an additive effect on aggregates, with the actin band decreasing as cooking times increased.

The kinetics of the formation of heterocyclic amines (HA) were measured on slices of Longissimus thoracis (LT) muscle subjected to impinging jets of superheated steam. Product temperature was either 170 or 200 degrees C and treatment duration ranged from 1 to 20 min. The concentrations of lQx, MelQx, 4,8-DiMelQx and PhIP followed regular kinetic patterns. HA formation increased significantly between 170 and 200 degrees C. The quantities of lQx and 4,8-DiMelQx formed in LT slices were 3 to 4-fold smaller than those formed in meat juices, while quantities of MelQx and PhIP remained comparable. A first-order kinetic model taken from the literature was adapted to describe the results taking into account product temperature variations over the course of the experiment.

International audience; The aim of this work was to reliably identify odour-active compounds in dry-cured ham using powerful analysis methods for the volatile fraction. For this purpose, dynamic headspace gas chromatography combined with eight-way olfactometry using a panel of eight sniffers was used. One- and two-dimensional gas chromatography coupled with mass spectrometry and (or) olfactometry were also used. More than 600 compounds from the volatile fraction of dry-cured ham were identified and their biochemical origins are discussed. They covered a wide diversity of structures and chemical functions. Only 29 of them proved odour-active. Comparison of the results of GC–O analysis with those obtained by orthonasal sniffing of the dry-cured ham helped to gain a better understanding of how these substances contributed to the overall aroma of the product. Thus, “Fruity–Floral”, “Green–Vegetable” or “Plastic–Chemical” odours intensively perceived by GC–O have been poorly perceived by orthonasal sniffing. By contrast, “Animal–Meat products” or “Butter–Lactic–Cheesy” odours have been much better perceived by orthonasal sniffing. These results indicate that to understand the interactions between odour-active compounds, experimental doping with carefully selected odour-active compounds will be necessary.

A histological and ultrastructural study was conducted to characterize changes in beef muscle structure after heating. Pieces of rectus abdominis muscle were heated at 100 degrees C over varying time frames from 15 min to 60 min and at 270 degrees C for 1 min; samples were then prepared for optical and transmission electron microscopy. After 15 min of heating, at 100 degrees C, a lateral shrinkage in fibre of 48% and an increase in gaps between the myofibrillar masses of 27% was noted. No more significant evolution was observed as heating duration escalated. The ultrastructure showed strong myofibril to sarcolemma detachments in which granular aggregates, coming in part from myofibrillar proteins, are stored. Neighbouring muscle Fibres showed strong heterogeneity in morphological behaviour after thermal treatment, suggesting that differences in composition and structure of the cytoskeleton proteins in the different fibres can cause denaturation/shrinkage of the proteins at different times along the timescale of microstructural changes during heating. Short heating at high temperatures expanded the gaps between myofibrillar mass, but the overall changes in the ultrastructure were similar to those obtained when heating at 100 degrees C.

The French AOC Taureau de Camargue guaranteed-origin breed certification was obtained in 1996. This denomination covers two local breeds, di Biou and Brave, and crossbreeds between them. On average, 2000 head of these beef cattle are raised every year, yielding 300 tons of meat. Little research has been done on these breeds, especially on meat quality. The aim of the work reported here was to characterise the muscles of these animals. Two muscles, semitendinosus and triceps brachii, were taken on slaughter from 10 males and 10 females from each of the two breeds. Colour, contractile and metabolic properties, intramuscular lipid contents and fatty acid composition were recorded for each sample. The results obtained highlight special features of the muscles of Taureau de Camargue cattle. Compared with all other French beef breeds, these muscles have a strongly oxidative metabolism, associated with a dark red colour and a very low proportion of IIx fast glycolytic fibers. They also contain very low levels of intramuscular lipids. Analysis of fatty acid composition revealed a particularly favourable dietary profile, with 15–20% polyunsaturated fatty acids and about 10% C18:3 fatty acids. We noted a darkening of the meat in both muscles from both breeds, and a strong propensity for myoglobin oxidation.

International audience; The formation of heterocyclic amines (HAs) was modelled in slices of longissimus thoracis (LT) and semimembranosus (SM) beef muscles subjected to jets of hot air at temperatures ranging from 170 and 250 degrees C and treatment times ranging from 1 to 20 min. The quantity of HAs formed in the SM muscle was clearly less that that formed in the LT muscle as soon as the heat treatment was longer than 300 s. The extreme dehydration obtained with the hot-air jets slowed the formation of IQx, MeIQx and, particularly, 4,8-DiM-eIQx compared with superheated steam treatments. The reverse effect was observed for PhIP concentrations which increased 1.4- to 5.5-fold. This highlights the important effect of water activity variations on HA formation, even at very low a(w) values.

International audience; The effect of meat cooking on protein aggregation was measured in pig M. Longissimus dorsi. Muscles were aged 4 days in air and then cooked at 100 degrees C for 10 or 30 min. Meat was ground in a KCl solution and the whole extract was delipidated with a mixture of butanol and di-isopropyl ether in a 40:60 v/v ratio. Protein aggregation induced by cooking was evaluated with a laser granulometer, which enabled reliable and reproducible characterisation of particle size distributions, and particle shape distributions using automated imaging techniques. Cooking significantly decreased the level of big particles, while the number of small particles remained stable. Cooking also affected the form and size of the particles. In order to better understand the mechanisms implicated in the aggregation process the level of protein oxidation and the protein surface hydrophobicity were evaluated in parallel with the granulometry measurements. Significant correlations were observed between the granulometry parameters and some of the protein oxidation indices. The protein surface hydrophobicity was also correlated with the granulometry parameters demonstrating the impact of thermal denaturation on the aggregation process.

A semi automatic flow procedure with photometric detection was developed for the study of meat protein digestion. This system comprised two independent flow pathways, gathered by two compartments. The gastric compartment was simulated by an ultrafiltration cell fitted with a 10 KDa cut off membrane and the intestinal compartment was simulated by a 1 KDa cut off dialysis membrane. The pathways were filled with solutions simulating digestive conditions. The proposed system was employed in digestion studies of whole protein extracts from raw and cooked (100°C) meat. A mathematical modelling for the determination of the digestive kinetic constants was established. The results show that meat cooking leads to an important decrease of protein digestibility by proteases of the digestive tract.

International audience; The present study used a proteomic data set obtained from a 2 x 2 x 2 factorial experiment on longissimus muscle of 24 pigs to identify single or couples of proteins allowing correct classification of pigs according to gender, sire breed, or rearing environment. An actin isoform, a myosin light chain 2 isoform and cytochrome Bc1 allowed each, correct classification of all pigs according to gender. Peroxiredoxin 6 allowed correct classification of 23 pigs according to indoor or outdoor rearing environment, but only if gender was also taken into account. Heat shock protein 73 allowed correct classification of 21 pigs according to sire breed, Duroc or Large White. Results show that proteins may be used as biomarkers for traceability or genetic research. Relationships between treatment factors and intracellular regulatory mechanisms associated with these proteins are discussed.

International audience; The technique of second derivative spectro photometry was used to determine the level and the heat stability of the three aromatic amino acids (tryptophan, tyrosine and phenylalanine) in bovine meat (M. Longissimus thoraci). This paper presents a method which measures the second derivative absorbance values at a wavelength specifically assigned to each aromatic amino acid with corrections for the interference from other amino acids at the same wavelength. Three cooking temperatures were tested in this study (60. 100 and 140 degrees C. Due to important cooking losses, results differ slightly according to the method of calculation (level expressed by gram of wet meat or by gram of proteins). Whatever the calculation method, heating at 60 degrees C had little effect on aromatic acid levels while higher temperatures had a dramatic effect on aromatic amino acids stability. The stability of the three aromatic amino acids during cooking decreased in the order tryptophan > phenylalanine > tyrosine

The effect of meat cooking was measured on myofibrillar proteins from bovine M. Rectus abdominis. The heating treatment involved two temperatures (100 degrees C during 5, 15, 30, and 45 min and 270 degrees C during 1 min). Protein oxidation induced by cooking was evaluated by the level of carbonyl and free thiol groups. Structural modifications of proteins were assessed by the measurement of their surface hydrophobicity and by their aggregation state. With the aim of evaluating the impact of heat treatment on the digestive process, myofibrillar proteins were then exposed to proteases of the digestive tract (pepsin, trypsin, and alpha-chymotrypsin) in conditions of pH and temperature that simulate stomach and duodenal digestion. Meat cooking affected myofibrillar protein susceptibility to proteases, with increased or decreased rates, depending on the nature of the protease and the time/temperature parameters. Results showed a direct and quantitative relationship between protein carbonylation (p0.01) and aggregation (p0.05) induced by cooking and proteolytic susceptibility to pepsin. However, no such correlations have been observed with trypsin and alpha-chymotrypsin.

1. Pectoralis major (P. major) muscle pH and meat quality traits were studied in relation to bird response to ante-mortem stress in three chicken lines: a fast-growing standard line (FGL), a slow-growing French 'Label Rouge' line (SGL) and a heavy line (HL). Ninety-nine birds of the three genetic types were slaughtered at their usual marketing age (6, 12 and 6 weeks for FGL, SGL and HL birds, respectively) on the same day. The birds of each line were divided into three different ante-mortem treatment groups: minimum stress (shackling for 10 s) (C), shackling for 2 min (SH) and acute heat plus shackling stress (exposure to 35 degrees C for 3.5 h and shackling for 2 min before stunning) (H + SH). 2. Regardless of chicken line, wing flapping duration (WFD) between hanging and stunning was strongly negatively related to P. major muscle pH at 15 min post-mortem. It was also moderately negatively related to P. major muscle glycolytic potential (GP), which represents glycogen level at death. Increasing WFD induced an increased ultimate pH (pHu) only in HL. The consequences of increased WFD for breast meat traits were dependent on the chicken line: it induced lower L* and b* and higher a* and drip loss in SGL while it only increased breast a* in HL birds. By contrast, WFD variations did not alter breast meat quality traits of FGL birds. Regardless of the chicken line, increased GP was associated with lower pHu and higher L* and drip loss. In SGL, it also increased b* and decreased curing-cooking yield of breast meat. 3. Struggling activity on the shackle line and muscle glycogen content at death could partly explain line and pre-slaughter variations in breast meat pH and quality traits. The water holding capacity of the raw and cooked meat was impaired by long shackling in the case of SGL birds while it was barely affected by ante-mortem conditions in the two standard lines. In conditions which minimised bird struggling (C), SGL and FGL birds had meat with a better water holding ability than that of broilers from the heavy line. However, when broilers were subjected to SH or H + SH conditions, the breast meat water holding capacity of SGL birds was lowered to the same level as that of the heavy line birds.

International audience; Pig semimembranosus muscles, sampled from normal hams or from PSE-zones of defective hams, were analysed by histochemistry and electrophoretic techniques. PSE zones were characterised by a disorganisation of fibre alignment and a significant increase of inter fibre spacing (26.2% vs. 16.9%, p < 0.05). Protein solubility was significantly lower in defective muscle (55.4 vs. 91.5 mg/g, p < 0.001). SDS-PAGE evidenced in such samples a lower abundance of the 97, 40 and 26 kDa bands in the sarcoplasmic fraction and a higher abundance of the 97, 58, 34, 31, 15 and 11 kDa bands in the myofibrillar fraction. Intensity of the MHC band (200 kDa) was lower in PSE zone samples. By 2-D electrophoresis, it was shown that troponin T, MLC 1 and alpha-crystallin were less proteolysed in defective muscles, while creatine kinase fragments were more represented. One form of HSP 27 was absent from PSE zone samples. Overall, meat from PSE-zones and fast pH fall-PSE meat show numerous histological and biochemical similarities, particularly in their protein characteristics.

In France, meat consumption represents one third of the total protein intake. Meat proteins have a high content of well-balanced essential amino acids near to Human needs. Meat is also a good source of vitamins B12 and iron. Its nutritional potential is thus very higher, but it could be modulated 1) by a protein digestion in the small intestine more or less complete (digestibility), determining the amount of absorbed amino acids, 2) by a speed of digestion higher or lower, affecting the postprandial utilization of absorbed amino acids in protein metabolism. Technological treatments involved in the meat preparation can generate physical-chemical changes of protein. Their impacts on the availability of constitutive amino acids (quantity, kinetics) have been little studied. After determining the impact of unitary operations on meat processing (aging, mincing, cooking) on the biochemical and structural characteristics of proteins, the effect on digestion parameters were studied in vitro on myofibrillar extracts, and in vivo using the minipig as an animal model. The proteomic approach is used in parallel to compare the composition of pig muscles from different rearing methods and study the correlations with digestion. Several protein markers of in vitro digestion are found for both aged and cooked meat, linked to detoxicant process and muscle contraction. The cooking is the process that has the greatest impact on characteristics of "ready-to-eat" product, the application of increasing temperatures (70, 100 and 140°C) resulting in a progressive combination of denaturation, oxidation and then of protein aggregation. Development of an in vitro digestion model (pepsin alone or coupled with trypsin/α-chymotrypsin), on myofibrillar proteins, was used to study the various parameters of digestion (initial slope, maximum rate, time to maximal rate, half-life time and maximal degradation) for the different processes. Aging and mincing have little impacts on these parameters. However, compared to raw meat, the rate of digestion is higher for a cooking temperature to 70°C, which is no longer the case for temperatures above 100°C. Conversely, the potential of maximal degradation is higher for temperatures above 100°C. Linking characteristics of meat with digestion parameters, suggests that for cooking temperatures of around 70°C, denaturation of proteins promotes rapid degradation of proteins by increasing the accessibility of digestive enzymes to their cutting sites, but for higher temperatures, oxidation leads to aggregates that limit accessibility. In vivo study on the minipig, confirms this hypothesis, the rate of appearance of amino acids in the blood following meat ingestion is higher with a core cooking temperature to 75°C, compared to cooking with 60 or 95°C. Furthermore, contrary to what observes in vitro, the use of meat labeled with a stable isotope (15N), we show that the cooking temperature are not affect the total amount of digested proteins in the small intestine (about 95% of ingested proteins). In conclusion, among the unitary operations involved in the preparation of meat, the cooking seems to be the one that most influence the digestion of proteins. The balance between the denaturation processes and protein oxidation according to the cooking temperature appears to be a key point in determining the speed of proteins digestion. This parameter is particularly important in the context of elderly nutrition. As it does not impact on the protein digestibility in the small intestine, the cooking temperature appears as an interesting lever to modulate the speed of meat protein digestion, according to the targeted consumer.; Les protéines carnées apportent tous les acides aminés indispensables, en quantité équilibrée par rapport aux besoins de l'Homme. La viande étant également une bonne source de vitamine B12 et de fer, son potentiel nutritionnel est très élevé. Ce potentiel pourrait cependant être modulé 1) par une digestion des protéines plus ou moins complète dans l'intestin grêle, déterminant la quantité d'acides aminés absorbés, 2) par une vitesse de digestion plus ou moins élevée, influençant la capacité d'assimilation des acides aminés absorbés. Les procédés de transformation impliqués dans la préparation des viandes peuvent générer des modifications physicochimiques des protéines. Leurs conséquences sur la mise à disposition des acides aminés constitutifs ont été peu étudiées. Après avoir déterminé l'impact des opérations unitaires de transformation de la viande sur les caractéristiques biochimiques et structurales des protéines, les conséquences sur les paramètres de digestion ont été étudiées, in vitro, sur des extraits myofibrillaires, et in vivo en utilisant le miniporc comme modèle animal. L'approche protéomique est utilisée, en parallèle, pour comparer la composition de muscles de porcs issus de modes d'élevage différents et étudier les corrélations avec la digestion. Plusieurs marqueurs protéiques des paramètres de digestion in vitro sont trouvés sur la viande maturée et cuite, et sont liés au processus de détoxification et de contraction musculaire. La cuisson est le procédé qui a le plus d'impact sur les caractéristiques du produit prêt à consommer, l'application de températures croissantes se traduisant par une combinaison progressive de dénaturation, d'oxydation puis d'agrégation des protéines. Le développement d'un modèle de digestion in vitro, sur des protéines myofibrillaires, a permis d'étudier les différents paramètres de digestion pour les différents procédés. Maturation et hachage ont eu peu d'effets sur ces paramètres. Par contre, par rapport à la viande crue, la vitesse de digestion est supérieure pour une température de cuisson de 70°C, ce qui n'est plus le cas à partir de 100°C. Inversement le potentiel de dégradation maximale est plus élevé pour des températures supérieures à 100°C. La mise en relation des caractéristiques de la viande, avec les paramètres de digestion, suggère que pour des températures de cuisson de l'ordre de 70°C, la dénaturation des protéines favorise une dégradation rapide des protéines en accroissant l'accessibilité des sites de coupure pour les enzymes digestives, mais que pour des températures supérieures, l'oxydation conduit à des agrégats qui limitent cette accessibilité. L'étude in vivo, sur le miniporc, a confirmé cette hypothèse, la vitesse d'apparition des acides aminés dans le sang, suite à l'ingestion des viandes étant supérieure pour une température de cuisson à coeur de 75°C, par rapport à des cuissons à 60 ou 95°C. Par contre contrairement à ce qui était observé in vitro, l'utilisation de viande marquée avec un isotope stable (15N), nous a permis de montrer que la température de cuisson n'affecte pas la quantité totale de protéines digérées dans l'intestin grêle (environ 95% des protéines ingérées). En conclusion, parmi les opérations unitaires impliquées dans la préparation des viandes, la cuisson semble être celle qui influence le plus la digestion des protéines. L'équilibre entre les processus de dénaturation et d'oxydation des protéines en fonction de la température de cuisson semble être un point clé dans la détermination de la vitesse de digestion des protéines. Ce paramètre est important notamment dans le cadre de la nutrition des personnes âgées. Par contre, les compensations au cours des étapes de la digestion font que ces différences de vitesses ne se traduisent pas par des différences de digestibilité dans l'intestin grêle.