Food microstructure and gastric digestion: the egg white gel model

Food microstructure and gastric digestion: the egg white gel model. STLOpenday

Characterization of egg white gel microstructure and its relationship with pepsin diffusivity

Understanding the diffusion of digestive enzymes, particularly pepsin, in different food structures, is a key factorto better control protein digestion and absorption. This study aimed to investigate how protein-based foodmicrostructure impacts pepsin diffusion. Two egg white gels (EWGs) of identical protein concentration (10%)but different structures were used as food models. The two different gel structures were prepared by heatingliquid egg white at pH5 and pH9, respectively. Results showed that egg white proteins formed a compact andmicrostructurally homogeneous gel at pH9 (mean particle size of 0.32 ± 0.02 μm, with a mean interparticledistance of 0.76 ± 0.07 μm), which leads to a lower FITC-pepsin diffusion coefficient(Deff=44.2 ± 6.1 μm2 s−1), compared to the pH5-EWG (Deff=52.5 ± 5.3 μm2 s−1). The microstructure ofthe pH5-EWG was characterised by a spatially heterogeneous loose protein matrix made of larger aggregateparticles (mean particle size of 0.76 ± 0.07 μm, with a mean interparticle distance of 1.79 ± 0.57 μm). Inaddition to the effects of the EWG microstructure, the environmental pH also affects the FITC-pepsin diffusion,likely because of the impact on electrostatic interactions between pepsin and the egg white proteins

Native lysozyme and dry-heated lysozyme interactions with membrane lipid monolayers: lateral reorganization of LPS monolayer, model of the E. coli outer membrane

International audienceLysozyme is mainly described active against Gram-positive bacteria, but is also efficient against some Gram-negative species. Especially, it was recently demonstrated that lysozyme disrupts Escherichia coli membranes. Moreover, dry-heating changes the physicochemical properties of the protein and increases the membrane activity of lysozyme. In order to elucidate the mode of insertion of lysozyme into the bacterial membrane, the interaction between lysozyme and a LPS monolayer mimicking the E. coli outer membrane has been investigated by tensiometry, ellipsometry, Brewster angle microscopy and atomic force microscopy. It was thus established that lysozyme has a high affinity for the LPS monolayer, and is able to insert into the latter as long as polysaccharide moieties are present, causing reorganization of the LPS monolayer. Dry-heating increases the lysozyme affinity for the LPS monolayer and its insertion capacity; the resulting reorganization of the LPS monolayer is different and more drastic than with the native protein

The role of Ovotransferrin in egg-white antimicrobial activity: a review

Eggs are a whole food which affordably support human nutritional requirements worldwide. Eggs strongly resist bacterial infection due to an arsenal of defensive systems, many of which reside in the egg white. However, despite improved control of egg production and distribution, eggs remain a vehicle for foodborne transmission of Salmonella enterica serovar Enteritidis, which continues to represent a major public health challenge. It is generally accepted that iron deficiency, mediated by the iron-chelating properties of the egg-white protein ovotransferrin, has a key role in inhibiting infection of eggs by Salmonella. Ovotransferrin has an additional antibacterial activity beyond iron-chelation, which appears to depend on direct interaction with the bacterial cell surface, resulting in membrane perturbation. Current understanding of the antibacterial role of ovotransferrin is limited by a failure to fully consider its activity within the natural context of the egg white, where a series relevant environmental factors (such as alkalinity, high viscosity, ionic composition, and egg white protein interactions) may exert significant influence on ovotransferrin activity. This review provides an overview of what is known and what remains to be determined regarding the antimicrobial activity of ovotransferrin in egg white, and thus enhances understanding of egg safety through improved insight of this key antimicrobial component of eggs

Comment structurer les aliments pour améliorer la biodisponibilité des nutriments et composés bioactifs

National audienc

From Bite to Nutrient: The Importance of Length Scales

Unravelling the mechanisms of food disintegration in the gastrointestinal tract should allow for a better understanding of the effect of food on human health. Several studies have reported the behavior of pure compounds (macronutrients or micronutrients) in digestive conditions. However, micronutrients and macronutrients are not often consumed as pure compounds but mostly embedded into food matrices. The structure of food products is now considered as a key parameter that strongly influences the release of nutrients in the gastrointestinal tract and their bioavailability in the bloodstream. This chapter therefore focuses on how the structure of foods and food constituents affects digestion. It shows that depending on the length scale that is chosen to follow food disintegration, data obtained can vary significantly

Statistical modelling of in vitro pepsinolysis using peptidomic data

International audienceProteins digestion is a complex and dynamic process involving several proteases that particularlydiffer in their specificity. The specificity of pepsin, the major protease of gastric digestion, has beenpreviouslyinvestigated,butonlyregardingtheprimarysequenceoftheproteinsubstrates. Thepresent study aimed to consider in addition physicochemical and structural characteristics, at themolecular and sub-molecular scales. For six different proteins submitted to in vitro gastric digestion,the peptide bonds cleaved were determined from the peptides released and identified by LC-MS/MS.An original statistical approach, based on propensity scores calculated for each amino acid residue onboth sides of the peptide bonds, concluded that preferential cleavage occurred after Leu and Phe, andbefore Ile. Moreover, reliable statistical models developed for predicting peptide bond cleavage,highlighted the predominant role of the amino acid residues at the N-terminal side of the peptidebonds,up to the seventh position (P7 and P7’). The significantinfluence ofhydrophobicity, chargeandstructuralconstraintsaround the peptidebonds wasalsoevidenced

Les Oeufs ? 60 clés pour comprendre

A quoi reconnaît-on un oeuf frais ? L'oeuf est-il un aliment gras ? Comment la poule fait-elle son oeuf ? L'oeuf en poudre est-il encore de l'oeuf ? A quoi correspondent les codes sur les oeufs du commerce ? Cet ouvrage nous décrit l'ensemble de la filière oeufs, de l'élevage des poules au produit consommé dans nos assiettes. Il fait le point sur la biologie et la physiologie des oeufs, leurs qualités nutritionnelles, leur production industrielle et leur transformation en ovoproduits ou pour des usages non alimentaires. Tout en nous donnant des conseils de stockage, de consommation, et même d'élevage pour ceux qui rêvent d'un poulailler, il démystifie au passage certains croyances erronées sur l'oeuf

Bioactive fractions of eggs for human and animal health

Volume 2 - Part III - Chap. 16 Eggs in nutritional and other applicationHen's eggs provide nutrients to the embryonic bird and protect it physically and microbiologically. Apart the physical barrier represented by shell, the constituents that eggs contains present biological functions vital for the protection of the embryonic bird. Thses constituents are consequently potential sources of bioactive fractions exploitable for medical, pharmaceutical, cosmetic, nutraceutical and biotechnological applications

Identification of the physicochemical characteristics of peptides that influence their hydrolysis by pepsin

Changing the structure of foods can modulate their nutritional quality by modifying the digestion process, a complex process that is still imperfectly understood. In particular, digestion dynamics have been poorly studied, although it can has significant metabolic consequences. The objective of this study is to model the proteolytic cascade by pepsin, and to highlight a potential "structural effect". Egg white is an interesting model to meet this dual objective, as it offers the possibility of obtaining gels with different structures. In a probabilistic modeling approach of the peptide cleavage dynamics, we sought to identify leverages for the cleavage of a peptide after a given digestion time. For this purpose, peptides are identified and quantified at different time points in an in vitro digestion experiment. A Generalized Additive Modeling of the probability of a cleavage based on the physicochemical profile of peptides is proposed, considering either all kinds of cleavages made by the pepsin or only those made on preferential peptide bonds. The most significant variables are related to the length of the peptide and its location on the ovalbumin sequence. These results suggest that the action of pepsin depends more on structural criteria than on the presence of specific cleavage sites