Effects of sodium nitrite reduction, removal or replacement on cured and cooked meat for microbiological growth, food safety, colon ecosystem, and colorectal carcinogenesis in Fischer 344 rats

Epidemiological and experimental evidence indicated that processed meat consumption is associated with colorectal cancer risks. Several studies suggest the involvement of nitrite or nitrate additives via N-nitroso-compound formation (NOCs). Compared to the reference level (120 mg/kg of ham), sodium nitrite removal and reduction (90 mg/kg) similarly decreased preneoplastic lesions in F344 rats, but only reduction had an inhibitory effect on Listeria monocytogenes growth comparable to that obtained using the reference nitrite level and an effective lipid peroxidation control. Among the three nitrite salt alternatives tested, none of them led to a significant gain when compared to the reference level: vegetable stock, due to nitrate presence, was very similar to this reference nitrite level, yeast extract induced a strong luminal peroxidation and no decrease in preneoplastic lesions in rats despite the absence of NOCs, and polyphenol rich extract induced the clearest downward trend on preneoplastic lesions in rats but the concomitant presence of nitrosyl iron in feces. Except the vegetable stock, other alternatives were less efficient than sodium nitrite in reducing L. monocytogenes growth

Analysis and modelling of mechanisms responsible of protein modifications during heating of meat tissue

L'amélioration de la qualité nutritionnelle des produits carnés cuits nécessite une meilleure compréhension des changements physicochimiques des protéines induits au chauffage. Ce travail porte sur l'analyse des mécanismes à l'origine des changements d'état des protéines afin de développer un modèle stoechio-cinétique de prédiction de l'effet de la composition et de la température sur ces changements. Un modèle expérimental, représentant l'environnement physicochimique du tissu musculaire (pH et force ionique), a permis de quantifier l'incidence spécifique de la chaleur, de la composition en fibres, en oxydants (fer, peroxyde d'hydrogène et vitamine C) et en antioxydants (enzymatiques, vitaminique et peptidique) sur l'oxydation, la dénaturation thermique et l'agrégation des protéines. Le modèle stoechio-cinétique est constitué de 43 réactions, représentant l'ensemble des phénomènes mis en jeu dans le modèle expérimental : chimie de Fenton, attaques radicalaires des acides aminés et dénaturation thermique. La résolution du système d'équations différentielles permet de calculer les concentrations des composés au cours du chauffage ; 3 constantes de vitesse inconnues ont été ajustées à partir des cinétiques expérimentales. Les résultats expérimentaux montrent : (1) un effet synergique des oxydants et du chauffage sur les oxydations, (2) une incidence négligeable des oxydants sur la dénaturation thermique et l'agrégation, (3) une sensibilité accrue des protéines de fibres α-white aux oxydations et à la dénaturation thermique par rapport à celles de fibres β-red et (4) un important effet de la nature des oxydants et des antioxydants sur les taux d'oxydation. Les prédictions du modèle stoechio-cinétique permettent de reproduire les tendances expérimentales. En partant de cette base, les modèles expérimentaux et mathématiques pourront être complexifiés progressivement pour avoir un outil prédictif de la qualité nutritionnelle des viandes cuites.Improving the nutritional quality of cooked meat products needs a better understanding of protein physicochemical changes induced by heating. This study aims to analyse the mechanisms responsible to protein state changes, in the goal to develop a predictive stoichio-kinetic model of effect of composition and temperature on these changes. An experimental model which represent the physicochemical environment of meat tissue (pH and ionic strength) allowed to quantify the specific effect of heating, composition in fibres, in oxidants (iron, hydrogen peroxide and vitamin C) and in antioxidants (enzymes, vitamins and peptides) on oxidations, thermal denaturation (hydrophobicity) and aggregation of proteins. The stoichio-kinetic model is composed of 43 reactions which represent all phenomenon involved in the experimental model : Fenton chemistry, radical attack on amino acids and thermal denaturation. A system of differential equation solver allows to determine the concentration of compounds during heating ; 3 unknown rate constants were adjusted with experimental kinetics. Experimental results show : (1) a synergistic effect of oxidants and heating on protein oxidation, (2) a negligible impact of oxidants on thermal denaturation and aggregation (3) a significant higher sensitivity to oxidation and thermal denaturation of protein from α-white than those from β-red, (4) an important effect of the composition in oxidants and antioxidants on the protein oxidation levels. Stoichio-kinetic model predictions reproduce experimental tendencies. From this base, experimental and stoichio-kinetic models could be progressively complexified to obtain a predictive tool of nutritional quality of meat

Développement d'un modèle mimétique de la viande pour l'étude des modifications physicochimiques des protéines au chauffage

National audienc

Kinetics of protein physicochemical changes induced by heating in meat using mimetic models: (2) Effects of fibre type, peroxides and antioxidants

International audienceHeating-induced changes in meat proteins were investigated using models made of aqueous suspensions of myofibrils according to muscle fibre types and cellular compounds (oxidants and antioxidants). These changes were evaluated by measurements of carbonyl groups and protein surface hydrophobicity. Model results were compared to trial results obtained on pork meat (M. Longissimus dorsi) heated under the same conditions (45 and 75 degrees C, from 5 to 120 min). Myofibrillar proteins from alpha-white fibres were more sensitive to oxidation and thermal denaturation than those from beta-red fibres. At 45 degrees C, there were negligible differences due to peroxide or antioxidant types. At 75 degrees C, organic peroxides (ROOH) were less oxidative than hydrogen peroxide (H2O2), and antioxidant enzymes were less efficient than vitamin E and camosine at protecting proteins against oxidation. Protein oxidation observed in meat is lower than in the mimetic models and the increase in hydrophobicity remained limited in meat. (C) 2012 Elsevier Ltd. All rights reserved

Analysis of free radical production in meat in the physicochemical conditions of storage and cooking

During meat processes (chilled storage, curing, cooking…), the production of free radicals (superoxide O2°- and hydroxyl HO°), due to iron reaction with oxygen and peroxides, leads to oxidative damages on proteins and lipids. Our aim was to determine and predict the kinetic laws governing the free radical production according to the physicochemical environment. Experiments were carried out on model systems which mimic the physicochemical conditions in meats during storage or cooking (pH 6, ionic strength of 0.24 M, and temperatures varying from 4 to 75°C) using the two major oxidants in meat: Fe2+ and H2O2. Free radical production kinetics were measured for many conditions using specific probes. A stoichio-kinetic mathematical model of the Fenton process which involved a Fe(II)/Fe(III) redox oxidative cycle was elaborated. Amounts of generated free radicals were related to temperature and iron content from the experiments and the activation energy of the chemical reaction that initiate O2°- production in biological systems was estimated at 55 kj/mol. from comparison of calculations with measurements

Développement d'un modèle mimétique de la viande pour l'étude des modifications physicochimiques des protéines au chauffage

National audienc

Modelling oxidation and denaturation of meat proteins during cooking

absen

Antioxidant supplementationis ineffective to reducethe frequency of pse-like zones in porkhams

International audienceThe frequency of pork hams with PSE-like zones is a major issue for the processed meat sector in France, despite recent improvements in the slaughter techniques and systematic sorting on the ultimate pH value of hams. Halothane genotype, still widespread in its heterozygous form, may play a significant role in this issue [1]. On the other hand, a recent work described at a molecular level a possible link between oxidative stress and the specific development of PSE-like zone [2]. From this hypothesis, an experimental design was carried out at the IFIP Experimental Station to evaluate the effect of antioxidant supplementation in pig diet on the appearance of PSE-like zone and more generally on the overall ham quality before and after cooking process

Early post-mortem sarcoplasmic proteome of porcine muscle related to protein oxidation

International audienceOxidative deterioration or modifications of proteins which appear during meat storage and processes can result in the impairment of technological, sensorial and nutritional qualities. Improving the quality involves a better understanding of the biochemical mechanisms responsible for protein oxidation in meat. For that purpose, an analysis was conducted to investigate the relationships between the early post-mortem sarcoplasmic proteome, which contains the majority of enzymes involved in the oxidative process, and protein oxidation generated during meat storage and cooking. This study was performed in Longissimus lumborum pig muscle. In order to have sufficient variability in the proteome and in the meat oxidation level, five groups of 10 animals issued from two different breeds and raised in three different rearing systems were analysed. Protein oxidation was estimated by the measurement of carbonyl groups after 1 and 4 days of refrigerated storage, and after 100 °C experimental cooking of the 4 days aged meat. Significant correlations (p < 0.05) were observed between the level of carbonyl groups and the intensities of 104 spots of the 2D electrophoresis, out of which 52 were clearly identified. The possible involvement of some proteins in the muscle oxidative stress leading to protein oxidation is discussed

A mimetic model to study the effect of meat compounds on protein modifications during heating

Meat cooking induces oxidations and conformation changes of proteins which can affect meat products quality and decrease their nutritional value. The aim of this paper was to investigate the effect of fiber type and cellular compounds (oxidants and antioxidants) on meat protein modifications (oxidation and denaturation) during heat treatments. Experiments were performed on a mimetic model composed of an aqueous suspension of myofibrillar proteins in a medium (pH and ionic strength) which reflected the muscle environment. Protein modifications were evaluated after 120 min heating (45°C or 75°C) by measurements of carbonyl groups and protein surface hydrophobicity. Results showed that myofibrillar proteins from glycolytic fibers were more sensitive to oxidation and thermal denaturation than proteins from oxidative fibers. Organic peroxide in interaction with iron induced less oxidation than hydrogen peroxide. Antioxidant enzymes were less efficient than vitamin E and carnosine to protect proteins against oxidation