Inhibitory effect of black tea, lemon juice, and other beverages on salivary and pancreatic amylases: What impact on bread starch digestion? A dynamic in vitro study

Certain food properties (ex.: pH, polyphenolic composition) can inhibit digestive amylases and thereby slowdown starch digestion. Our aim was twofold. (1) To determine the impact of 21 beverages and condiments(coffees, teas, wines, vinegars and lemon juice) on salivary and pancreatic amylolysis: inhibition ranged from10% to 100% in our experimental conditions. (2) To investigate the effect of one black tea and lemon juice(selected for their strong inhibitory capacity) on starch hydrolysis during dynamic oro-gastro-intestinal digestionof bread. Compared to water (control), the effect of black tea was limited to a ≈20% reduction of releasedoligosaccharides during the intestinal phase. Lemon juice had a remarkable effect, completely interruptinggastric amylolysis by salivary amylase via a preliminary acidification of gastric contents. These results provide astrong biochemical rationale for the development of dietary strategies to improve the glycaemic impact ofstarch-rich meals which could be tested in vivo

Structurer l'aliment pour mieux piloter sa déconstruction dans le tube digestif et optimiser la biodisponibilité des nutriments.

Dans un contexte réglementaire contraint et une demande sociale et sociétale en pleine évolution, une refonte complète de l’ouvrage « Aliments fonctionnels » voit le jour. Grâce à la contribution de plus d’une cinquantaine d’experts aux compétences complémentaires, « Aliments fonctionnels » s’enrichit d’approches nouvelles en lien avec la durabilité des systèmes alimentaires.Ainsi cet ouvrage fournit de multiples pistes de réflexion et de nombreux axes de recherche pour l’innovation alimentaire.Aux chapitres des précédentes éditions entièrement réactualisés, s’ajoutent des volets illustrant les comportements, les inégalités sociales, la compréhension des messages, l’acceptabilité des innovations et les enjeux de la durabilité.Ce livre présente donc des questions nouvelles en lien avec la sécurité alimentaire du consommateur et les perspectives d’évolution de la démographie mondiale.« Aliments fonctionnels » s’adresse aux ingénieurs en R&D agroalimentaire, aux professionnels de la nutrition et de l’alimentation, de la santé, aux spécialistes du marketing, de l’innovation et de la communication et à tous les acteurs de la sécurité alimentaire.Les dernières décennies ont vu une augmentation spectaculaire, à l’échelle internationale,des pathologies liées à l’aliment et à l’alimentation. Le surpoids et ses conséquences tellesque les maladies cardiovasculaires ou le diabète de type 2 touchent environ 1,5 milliard d’adultes dans le monde et la plupart des prévisions prévoient que ce chiffre atteindra 3 milliards d’individus à l’horizon 2030. On estime à près de 3 millions le nombre de personnes décédant chaque année du fait de leur surpoids ou de leur obésité. En France, 6,5 millions de personnes sont considérées comme obèses. La proportion des personnes obèses est ainsi passée de 8,5 % à 14,5 % entre 1997 et 2009. L’augmentation de la prévalence est observée dans toutes les tranches d’âge de la population, y compris chez les séniors, avec une exacerbation chez les femmes (15,1 %) par rapport aux hommes (13,9 %). L’augmentation de l’obésité est majoritairement liée à (1) une plus grande consommationd’aliments très caloriques riches en graisses et (2) un manque croissant d’activité physique en raison de la nature de plus en plus sédentaire de nombreuses formes de travail, de l’évolution des modes de transport et de l’urbanisation. Malgré de multiples campagnes de sensibilisation, force est de constater qu’il est difficile de contraindre les personnes en surpoids à accroître leur activité physique. Une des solutions possibles serait donc de proposer au consommateur une offre alimentaire moins calorique, tout en présentant lesmêmes propriétés de rassasiement et de satiété

Scale-down emulsion homogenization: Conditions to mimic pilot homogenizer depending on the emulsifier

The standard tool for emulsification during formulation trials is a homogenizer, which unfortunately requires toomuch raw material and is time consuming. A lab-scale process using a rotor-stator shearing step followed byultrasound treatment was designed, both with lecithin and whey protein, for emulsification as efficient as inpilot-plant trials. Ranges for the lab-scale process were defined (rotor-stator: 5 min, 5000–10000 rpm; sonicationtime: 2–10 min). Process conditions were identified to obtain both emulsions with the same structure at lab andpilot scales: for lecithin, respectively shearing at 10000 rpm/10 min sonication and high pressure for both pilotstages. However, due to protein denaturation, some conditions differed for whey proteins: shearing at 5000 rpminstead of 10000 rpm (all the other parameters being unchanged). Finally, recommendations concerning theposition of the ultrasound probe and temperature control are provided to insure good reproducibility

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

Mathematical modelling of food digestion

Mathematical modelling of food digestion. STLOpenday

Diffusion de sondes moléculaires mesurée par RMN à gradient de champ pulsé : Application à l'étude de l'évolution de la structure des systèmes caséiques au cours de la formation des gels

The aim of this study was to investigate the impact of the casein gel microstructure on molecular diffusion.The first part of this work aimed at studying the diffusion of polyethyleneglycols (PEGs) of various sizes, used as molecular probes, in casein gels that had different microstructures. Variations in diffusion coefficient values were related to the network porosity. In the second part of this work, these results were supplement by a continuous investigation of probe diffusion by NMR during the formation of casein gels. Two PEG sizes were selected and their diffusion coefficients were measured throughout the rennet, acid and combined coagulation processes. The evolution of the small probe diffusion was related to modifications in structure and porosity of casein aggregates, whereas the diffusion of the large probe was explained by network porosity. The comparison of these results with rheological measurements and scanning electron microscopy images revealed the potential of the pulsed field gradient NMR technique to study casein matrix microstructures at different length-scales.L'objectif de ce travail était d'étudier l'influence qu'exerce la microstructure des matrices laitières sur la diffusion moléculaire.Une première partie de ce travail a permis d'étudier la diffusion de sondes de taille variable, des polyéthylèneglycols (PEGs), dans des gels de caséines ayant différentes structures. Les variations des coefficients de diffusion ont été reliées à la porosité du réseau. Dans un second temps, ces résultats ont été complétés par la mesure en continu de la diffusion de sondes par RMN au cours de la formation des gels de caséines. Deux tailles de PEG ont été sélectionnées et leur diffusion a été mesurée au cours des procédés de coagulation présure, acide et mixte. L'évolution de la diffusion de la sonde de petite taille a été reliée aux modifications de structure et de porosité des agrégats micellaires, tandis que la diffusion du PEG de plus grande taille a été expliquée par la porosité du réseau. La confrontation de ces résultats avec des mesures rhéologiques et des images de microscopie électronique à balayage a permis de mettre en évidence les potentialités de la technique RMN à gradient de champ pulsé pour étudier les microstructures des matrices caséiques à différentes échelles

Oro-gastro-intestinal digestion of starch in white bread, wheat-based and gluten-free pasta: Unveiling the contribution of human salivary α-amylase

International audienceStarch is a major determinant of the glycemic responses elicited by our diets, but the exact contribution of the two main amylolytic enzymes (salivary and pancreatic alpha-amylases) remains a matter of debate. Our aim was to investigate the contribution of the oral, gastric and intestinal phases to the hydrolysis of starch in bread and pasta during dynamic in vitro digestions using DiDGI (R). Before its inactivation by the low gastric pH, salivary alpha-amylase released about 80% of the starch in bread and 30% of that in pasta, hydrolysing over half of it into oligosaccharides. Accordingly, the contribution of pancreatic alpha-amylase during the intestinal phase was lower for bread than pasta. Our results are well correlated with in vivo data, and demonstrate the importance of salivary alpha-amylase during oro-gastric processing of starchy foods. This finding is discussed in relation with observations regarding salivary alpha-amylase from other fields of knowledge

A NMR Self-Diffusion Study of Casein Species during the Rennet Coagulation of a Dairy Solution

International audienceRennet coagulation constitutes the critical first step in the manufacture of most cheese varieties and consists in three main phases: enzymatic reaction, sol-gel transition and structural rearrangements during aging. In this study, we investigated the rennet coagulation of a concentrated casein suspension using pulsed field gradient (PFG)-NMR. Dynamic rheological measurements were also performed for comparison. Two main types of casein species were distinguished according to their diffusing properties. The first one was attributed to the pool of dissociated caseins and caseinomacropeptides (CMP) and the second one to casein particles. The amount of NMR signal coming from dissociated molecules increased all along the experiment (Figure 1-A) whereas the opposite behaviour was characterized for casein particles. This could be explained by the increasing amount of CMP in the whey and the reciprocal loss of protons in the casein particles as the enzymatic reaction proceeded, and used to quantitatively estimate the kinetics of the chymosin action. The diffusion of dissociated molecules was poorly sensitive to the coagulation process. However, if the diffusion of casein particles remained unmodified during the early stages of the chymosin action, it decreased by more than 30 % during the sol-gel transition and then increased in similar proportions during the gel aging phase (Figure 1-B), thereby showing the great sensitivity of the particle dynamics to the structural evolution of the sample. Hence, all the major phenomena that are known to take place could be characterized simultaneously. Moreover, our results show that all casein particles did not aggregate during the sol-gel transition which suggests that for concentrated dairy samples, in supplement to the structural rearrangement processes, a delayed aggregation might also contribute to the stiffening of the gel during the aging phase. It is conclude that PFG-NMR has a great potential to better understand the mechanisms of dairy coagulation processes

NMR diffusometry as a tool to investigate the rennet coagulation of a concentrated dairy solution

International audienceRennet coagulation constitutes the critical first step in the manufacture of most cheese varieties and consists in three main phases : enzymatic reaction, sol-gel transition and structural rearrangements during aging. In this study, we investigated the rennet coagulation of a concentrated casein suspension using pulsed field gradient (PFG)-NMR. Dynamic rheological measurements were alson performed for comparison. Two main types of casein species were distinguished according to their diffusing properties. The first one was attributed to the pool of dissociated caseins and caseinomacropeptides (CMP) and the second one to casein particles.The amount of NMR signal coming from dissociated molecules increased along the experiment whereas the opposite behaviour was characterized for casein particles. This could be explained by the increasing amount of CMP in the whey and the reciprocal loss of protons in the casein particles as the enzymatic reaction proceeded, and used to quantitatively estimate the kinetics of the chymosin action. The diffusion of dissociated molecules was poorly sensitive to the coagulation process. However, if the diffusion of casein particles remained unmodified during the early stages of the chymosin action, it decreased by more than 30% during the sol-gel transition and then increased in similar proportions during the gel aging phase, thereby showing the great sensitivity of the particle dynamics to the structural evolution of the sample. Hence, all the major phenomena that are known to take place could be characterized simultaneously. Morevover, our results show that all casein particles did not aggregate during the sol-gel transition which suggests that for concentrated dairy samples, in supplement to the structural rearrangement processes, a delayed aggregation might also contribute to the stiffening of the gel during the aging phase. It is conclude that PFG-NMR has a great potential to better understand the mechanisms of dairy coagulation processes

PFG-NMR: a versatile tool for microstructure investigation of dairy protein gels

International audienceIn the present study, we illustrate the potentiality of the PFG-NMR technique to investigate structural changes in dairy casein gels. Casein is the main milk protein component. It exists in milk as a suspension of large spherical particles called casein micelles. These colloidal particles can be destabilized in different ways, by addition of rennet, by slow acidification, or by combinations of both. Various parameters influence the dynamics of the coagulation process. Depending on these conditions, the gel microstructure and its rheological properties, which are very important attributes of the product, can therefore be very different. To improve our understanding of the microstructure, different PFG-NMR approaches have been carrying out. The diffusion coefficient of poly(ethylene glycol) (PEG) polymers with varying molecular weights, used as probe, were compared in casein gels obtained with different coagulation processes [1,2]. A time-resolved PFG-NMR method to investigate how and when probe diffusion rates vary during the coagulation process of dairy protein was also implemented [2,3]. The last example will we focus on the study of the self-diffusion of non-aggregated casein molecules used as probe and compared with PEG [4]