The harmonized INFOGEST in vitro digestion method: From knowledge to action

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

Evolutions structurales et oxydation des lipides lors de la digestion in vitro d'émulsions modèles

Recent data show that the nutritional benefits associated to the consumption of n-3 polyunsaturated fatty acids depend on the fate of lipid structures, including lipid oxidation, during digestion. The aim of this work was to determine the influence of the composition of digestion media on the evolution of the structures of emulsified lipids and the bioaccessibility and the oxidation of fatty acids. In vitro gastrointestinal digestion conditions, based on analysis of the literature and taking into account the constraints related to gas exchanges, were first set up and then used to digest emulsions stabilized by a protein or by surfactants. Interestingly, malonaldehyde, 4-HNE and 4-HHE were formed during both the gastric and intestinal phases. The results show contrasting effects of the gastric conditions, the emulsifier, the presence of metmyoglobin, and the fatty acid and tocopherols compositions of the oils on flocculation and coalescence of the emulsions, kinetics of lipolysis during the intestinal phase, and oxidation. The importance on oxidation of the balance between pro- and anti-oxidants, unsaturation and chain length of the fatty acids has been also confirmed. Depending on the nature of the emulsifier and the dispersion state of lipids at the beginning of intestinal phase the digestive juices exhibit or not protective effect on oxidation. The in vitro oxidation data were compared with results obtained in vivo in the gut contents and plasma of mice.Les données récentes montrent que les bénéfices nutritionnels associés aux acides gras polyinsaturés n-3 dépendent du devenir des structures des lipides et de leur oxydation au cours de la digestion. L’objectif de cette thèse était de préciser l’importance de paramètres liés à la composition des milieux de digestion sur les évolutions des structures des lipides émulsifiés, la bioaccessibilité des acides gras, et leur oxydation. Après la mise au point de conditions de digestion in vitro basées sur l’analyse de la bibliographie et prenant en compte des contraintes liées aux échanges gazeux, des digestions gastro-intestinales ont été effectuées sur des émulsions stabilisées par une protéine ou des tensioactifs. Les résultats montrent des effets contrastés des conditions gastriques, de la nature de l’émulsifiant, de la composition en acides gras et en tocophérols des huiles et de la présence de metmyoglobine sur la floculation et la coalescence des émulsions et sur les cinétiques de lipolyse intestinale et d’oxydation. L’importance de la balance entre pro et antioxydants, de l’insaturation et de la longueur de chaîne des acides gras, ainsi que de la présence des sucs digestifs ont ainsi été démontrés sur l’oxydation des acides gras selon la nature de l’émulsifiant et l’état de dispersion des lipides lors de leur arrivée en phase intestinale. Ainsi, le malonaldéhyde, les 4-HNE et 4-HHE sont formés pendant les phases gastrique et intestinale. Les données sur l’oxydation in vitro ont été comparées avec des résultats obtenus in vivo dans le contenu digestif et dans le plasma chez la souris

Lipid oxidation in food emulsions under gastrointestinal-simulated conditions: the key role of endogenous tocopherols and initiator

The health significance of lipid oxidation productscarried by the diet or eventually formed during food digestion isactually addressed. Accordingly, some data show that the gas-tric environment could be prooxidant. The aim of this work wasto evaluate the impact of the balance between lipophilic anti-oxidant species and dietary prooxidant on lipid oxidation underin vitro gastrointestinal conditions. Rapeseed oil-in-water emul-sions stabilized by bovine serum albumin were submitted suc-cessively to simulated stomach and intestinal conditions. Lipidoxidation was evaluated through the measurement of oxygenconsumption, the formation of hydroperoxides and malonalde-hyde (MDA). With endogenous tocopherols (553 mgkg−1oil)and without initiator no oxygen was consumed, while thepresence of metmyoglobin (20 μM) induced a low oxygenconsumption and formation of MDA during the gastric (73±13 nmolg−1lipids) and intestinal steps (163±13 nmolg−1lip-ids). Without endogenous tocopherol (<2 mgkg−1oil) and withmetmyoglobin (20μM), amounts of hydroperoxides and MDAreached 79±28μmolg−1lipids and 2,139±78 nmolg−1lipids,respectively, after the gastric phase and 113±22μmolg−1lipidsand 2,663±38 nmolg−1lipids during the intestinal phase. Theresults indicate that the composition of the food bolus, inparticular the presence of lipophilic antioxidant and/or proox-idant species, is critical for the oxidative fate of emulsifiedlipids during digestion. Moreover, the physicochemical condi-tions of the digestion, rather than the constituents of simulateddigestive fluids, seemto favor lipid oxidation

The initial characteristics of marine oil emulsions and the composition of the media inflect lipid oxidation during in vitro gastrointestinal digestion

International audienceThis work aimed at evaluating the effect of simulated digestive fluids, interface and lipid droplet sizes on the oxidation of oil-in-water emulsions containing long chain n-3 fatty acyls. Emulsions stabilised by a protein or by phosphatidyl-choline/Tween 80 were submitted to gastro-intestinal in vitro conditions in presence of metmyoglobin. The gastric phase was characterised by a decrease of tocopherol amounts and moderate O-2 uptake and aldehyde formation. Oxidation developed further during the intestinal phase, with tocopherols tending to zero, oxygen uptake and production of aldehydes at potentially toxic concentrations. The simulated digestive fluids reduced oxygen uptake and MDA formation only during the intestinal step of the phospholipid-stabilised emulsion. Quantitative losses of PUFA (e.g. EPA, DHA) were less than 10% even significant at the end of the digestion

Devenir digestif et effets métaboliques des matrices formulées à base de lipides

Chapitre 14 Partie 3 : des matrices complexes aux effets métaboliques et santéNational audienc