Ferulic Acid and Eugenol Have Different Abilities to Maintain Their Inhibitory Activity Against Listeria monocytogenes in Emulsified Systems

Natural phenolic compounds are found in large quantities in plants and plant extracts and byproducts from agro-industries. They could be used to ensure food quality and safety due to their antimicrobial properties demonstrated in systems such as culture media. The aim of this study was to evaluate the ability of two natural phenolic compounds, ferulic acid and eugenol, to maintain their inhibitory activity against the growth of Listeria monocytogenes in an oil-in-water emulsion, simulating a complex food system. The minimum inhibitory concentration (MIC) of each phenolic compound was first determined in culture medium, consisting of TS broth and an added emulsifier. Whey proteins and Tween 80 increased the MIC of the antimicrobial activity of eugenol. The MIC of ferulic acid was less affected by the addition of Tween 80. The inhibitory activities of both phenolic compounds were then compared at the same concentration in emulsions and their corresponding aqueous phases by following the growth of L. monocytogenes by plate counting. In emulsified systems, eugenol lost the high inhibitory activity observed in the aqueous phase, whereas ferulic acid retained it. The partition coefficient (logPoct/wat) appears to be a key factor. Eugenol (logPoct/wat = 2.61) dispersed in the aqueous phase intercalates into the bacterial membrane and has high antimicrobial activity. In contrast, it likely preferentially partitions into the lipid droplets when dispersed in an emulsion, consequently losing its antimicrobial activity. As ferulic acid is more hydrophilic, a higher proportion probably remains in the aqueous phase of the emulsion, retaining its antimicrobial activity

Mise en place concertée d’actions pour éviter le ruissellement érosif en Pays de Caux : Projet SURGE – Programme Eaux et territoires

Les 16 et 17 mars 2016, l’AFEPTB a organisé un séminaire technique à l’attention de l’ensemble des agents des EPTB. L’organisation de séminaires techniques constitue une initiative nouvelle de l’AFEPTB. Cela fait suite à des discussions sur les groupes de travail thématiques qui se réunissaient de manière régulière par le passé. L’idée est désormais de proposer 2 temps de 2/3 jours par an à l’ensemble des agents des EPTB sur plusieurs thématiques et de manière transversale. Les objectifs poursuivis sont de mieux se connaître et de travailler sur des dossiers transversaux. Les séminaires alternent des interventions spécialisées, des retours d’expériences, des échanges et temps de co-construction

Erratum : Stabilité des huiles alimentaires au cours de leur stockage

Vegetable oils are chemically unstable due to the sensitivity to oxidation of their unsaturated fatty acids. The oxidative mechanisms are based on complex and radical reactions that always result in a significant loss of oil quality in both sensorial (rancidity) and nutritional values (loss of polyunsaturated fatty acids and vitamin E). Monitoring the oxidation state of oil can be performed using different markers, each bringing a partial information of the whole phenomenon, but unable to predict by itself the future stability of the oil. The accelerated ageing tests used in reasonable heating conditions are useful for measuring the resistance of oil to oxidation but are difficult to extrapolate to normal storage conditions. The oxidative degradation of oil during storage can be delayed by protecting it from light, heat, oxygen and metals. Another way consists to increase the retention of endogenous antioxidants naturally contained in the oil seeds, such as tocopherols (vitamin E), which are partially removed during conventional operations of extraction and refining

Stabilité des huiles alimentaires au cours de leur stockage

Vegetable oils are chemically unstable due to the sensitivity to oxidation of their unsaturated fatty acids. The oxidative mechanisms are based on complex and radical reactions that always result in a significant loss of oil quality in both sensorial (rancidity) and nutritional values (loss of polyunsaturated fatty acids and vitamin E). Monitoring the oxidation state of oil can be performed using different markers, each bringing a partial information of the whole phenomenon, but unable to predict by itself the future stability of the oil. The accelerated ageing tests used in reasonable heating conditions are useful for measuring the resistance of oil to oxidation but are difficult to extrapolate to normal storage conditions. The oxidative degradation of oil during storage can be delayed by protecting it from light, heat, oxygen and metals. Another way consists to increase the retention of endogenous antioxidants naturally contained in the oil seeds, such as tocopherols (vitamin E), which are partially removed during conventional operations of extraction and refining

Influence des protéines laitières sur le pouvoir antioxydant et la biodisponibilité des polyphénols du café

MASSY-AgroParisTech (913772301) / SudocSudocFranceF

Mesure et prédiction de la réactivité des lipides au cours du chauffage d'huiles végétales à haute température

Si les lipides contribuent à la valeur nutritionnelle et sensorielle de nombreux aliments, ils sont particulièrement sensibles aux réactions d'oxydation. Les principaux mécanismes mis en jeu lors de l'oxydation des acides gras insaturés sont relativement bien connus. En revanche, il est aujourd'hui quasiment impossible de prédire l'avancement des réactions et souvent nécessaire de recommencer une nouvelle étude de stabilité oxydative pour tout nouveau couple produit alimentaire / procédé de transformation. L'objectif de la thèse est donc de construire un modèle mécanistique couplé à un modèle de transfert de l'oxygène dans le but de prédire l'avancement des réactions d'oxydation dans un milieu lipidique continu et dans des conditions expérimentales définies et contrôlées (température, oxygénation, composition en acides gras, composition en antioxydants). Pour cela, un schéma réactionnel visant à détailler l'ensemble des réactions impliquées dans le phénomène d'auto-oxydation des lipides a été proposé puis un modèle stoechio-cinétique a été construit à partir des valeurs des paramètres cinétiques issues de la littérature. La réactivité des acides gras insaturés présents dans trois huiles végétales d'usage courant (colza, tournesol, tournesol oléique), purifiées de leurs antioxydants naturels, a été étudiée entre 80 et 180C, en suivant différents marqueurs d'oxydation (diènes conjugués, hydroperoxydes, aldéhydes, polymères). Comme attendu, les cinétiques d'oxydation se sont avérées dépendantes de la composition des huiles en acides gras, de la température et des conditions d'oxygénation. L'ajout d'antioxydant(s) a confirmé l'effet protecteur de l'a-tocophérol, qui n'a pas été amélioré par un enrichissement en acide chlorogénique, acide phénolique naturellement présent dans les graines de tournesol. Les résultats obtenus ont été utilisés pour valider le modèle développé, dont les prédictions permettent de reproduire les tendances expérimentales. Deux limitations ont été mises en évidence au cours de cette phase de validation dont la première concerne la description fiable et précise du mécanisme d'oxygénation du milieu, qu'il sera nécessaire de mesurer dans une huile à haute température pour valider le modèle d'oxydation. Par ailleurs, compte tenu du nombre important de réactions prises en compte, il sera indispensable de disposer d'un jeu de données expérimentales plus important, pouvant inclure des intermédiaires radicalaires. Pour cela, les potentialités de la résonance paramagnétique électronique ont été étudiées au cours de ce travail, à la fois pour suivre les radicaux lipidiques et pour accéder à des paramètres cinétiques pour des réactions radicalaires, peu disponibles dans la littérature.If lipids contribute to nutritional and sensorial properties of many foodstuf, they are particularly sensitive to oxidation reactions. The main mechanisms involved in the oxidation of unsaturated fatty acids are already well-known. However, it is almost impossible to predict the progress of oxidative reactions and often necessary to develop new studies of oxidative stability for each new food product / processing. The aim of this study is to develop a mechanistic model coupled to oxygen transfer in order to predict the evolution of oxidation reactions in a bulk lipid system and in defined and controlled experimental conditions (temperature, oxygenation, fatty acids' composition, antioxidants' composition). Thus, a reaction scheme detailing all the reactions involved in the oxidation phenomenon was proposed and a stoichio-kinetic model was built on the basis of conservation equations and kinetic parameters available in literature. The reactivity of unsaturated fatty acids contained in three usual edible oils (rapeseed, sunflower, high oleic sunflower), previously stripped of their natural antioxidants, was studied between 80 and 180 C, following several oxidation markers (conjugated dienes, hydroperoxides, aldehydes, polymers). As expected, oxidation kinetics depended on fatty acids' composition of oils, on temperature and on oxygen availability. The addition of antioxidant(s) confirmed the protective effect of a-tocopherol, which was not improved by the enrichment in chlorogenic acid, a phenolic acid naturally occurring in sunflower seeds. The experimental data were used to validate the model which predictions reproduce experimental tendencies. Two limitations were identified during model validation. The first is the accurate description of the oxygenation mechanism of the medium which need to be measured in oil at high temperatures. Moreover, given the large number of reactions taken into account, it is essential to have a set of more important experimental data which include radical intermediates. For this, the potential of electron spin resonance spectroscopy was evaluated in this in order to follow lipid radical species and access to kinetic parameters of radical reactions, few available in literature.PARIS-AgroParisTech Centre Paris (751052302) / SudocSudocFranceF

Stratégies pour éviter l'épuisement des infirmières en psychiatrie lors de la prise en charge des patients toxicomanes: une revue étoffée de littérature

De nos jours, les gens et même les professionnels de la santé peuvent avoir des stéréotypes et des représentations négatives des toxicomanes. En effet, ces derniers sont encore très stigmatisés et ne reçoivent pas toujours des soins adéquats. De nombreux facteurs rendent le travail en psychiatrie difficile et stressant. Cela est encore accentué lors des prises en charge des toxicomanes en lien avec leur caractère impulsif, leur exigence et les nombreuses rechutes. Le travail en psychiatrie ainsi que les soins prodigués aux personnes dépendantes peuvent être une source de fatigue pour les infirmières. L’épuisement professionnel peut très vite s’installer

Ferulic acid and eugenol have different abilities to maintain their inhibitory activity against Listeria monocytogenes in emulsified systems

Natural phenolic compounds are found in large quantities in plants and plant extracts and byproducts from agro-industries. They could be used to ensure food quality and safety due to their antimicrobial properties demonstrated in systems such as culture media. The aim of this study was to evaluate the ability of two natural phenolic compounds, ferulic acid and eugenol, to maintain their inhibitory activity against the growth of Listeria monocytogenes in an oil-in-water emulsion, simulating a complex food system. The minimum inhibitory concentration (MIC) of each phenolic compound was first determined in culture medium, consisting of TS broth and an added emulsifier. Whey proteins and Tween 80 increased the MIC of the antimicrobial activity of eugenol. The MIC of ferulic acid was less affected by the addition of Tween 80. The inhibitory activities of both phenolic compounds were then compared at the same concentration in emulsions and their corresponding aqueous phases by following the growth of L. monocytogenes by plate counting. In emulsified systems, eugenol lost the high inhibitory activity observed in the aqueous phase, whereas ferulic acid retained it. The partition coefficient (logP(oct/wat)) appears to be a key factor. Eugenol (logP(oct/wat) = 2.61) dispersed in the aqueous phase intercalates into the bacterial membrane and has high antimicrobial activity. In contrast, it likely preferentially partitions into the lipid droplets when dispersed in an emulsion, consequently losing its antimicrobial activity. As ferulic acid is more hydrophilic, a higher proportion probably remains in the aqueous phase of the emulsion, retaining its antimicrobial activity

Carnosic acid from rosemary extracts limits oxidation in edible oils and protects endogenous alpha-tocopherol : a mechanistic approach

Carnosic acid from rosemary extracts limits oxidation in edible oils and protects endogenous alpha-tocopherol : a mechanistic approach. 28. International Conference on Polyphenol