Françoise Nau

• PhD
• Professor at Institut Agro Rennes-Angers

The increasing demand for food and especially proteins leads to the search for alternative protein sources. Meat co-products, which are available but little used in human food, provide a potential solution to this challenge. The present study aimed to evaluate the nutritional quality of two beef protein ingredients (greasy greaves recovered protein...

The valorization of co-products may be a promising way to meet the dual challenge of increasing global food resources and sustainability of food systems. In particular, meat co-products may be nutritionally interesting protein resources, if they offer functional properties in accordance with food applications. In that aim, two bovine co-products, r...

The monitoring of food degradation during gastrointestinal digestion is essential in understanding food structure impacts on the bioaccessibility and bioavailability of nutrients. Magnetic Resonance Imaging (MRI) has the unique ability to access information on changes in multi-scale structural features of foods in a spatially resolved and non-destr...

Résumé Étudier les mécanismes de désintégration des aliments dans le tractus gastro-intestinal doit permettre de mieux comprendre l’effet des aliments sur la santé humaine. De nombreuses études ont rapporté le comportement de composés purifiés (macro ou micronutriments) en conditions digestives. Cependant, les micro et macronutriments sont rarement...

While there is a consensus that food structure affects food digestion, the underlying mechanisms remain poorly understood. A previous experiment in pigs fed egg white gels of same composition but different structures evidenced such effect on food gastric disintegration. In this study, we detailed the consequences on intra-gastric pH, pepsin concent...

Pepsin diffusion in food particles during gastric digestion is one of the main factors limiting proteolysis kinetics. Diffusion coefficients of pepsin are needed as input parameters for in silico models of digestion, but no values are currently available in real foods. The challenge of this study was to apply the Fluorescent Recovery After Photoble...

The hen's egg (Gallus gallus) is an animal product of great agronomic interest, with a world production of 70.9 million tonnes in 2018. China accounted for 35% of world production, followed by North America (12% of world production), the European Union (7.0 million tonnes, 10% of world production) and India (5.0 million tonnes, 7% of world producti...

The specificity of pepsin, the major protease of gastric digestion, has been previously investigated, but only regarding the primary sequence of the protein substrates. The present study aimed to consider in addition physicochemical and structural characteristics, at the molecular and sub-molecular scales. For six different proteins submitted to in...

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...

A recent work revealed that egg white (EW) at 45 °C exhibits powerful bactericidal activity against S. enterica serovar Enteritidis, which is surprisingly little affected by removal of the >10 kDa EW proteins. Here, we sought to identify the major EW factors responsible for this bactericidal activity by fractionating EW using ultrafiltration and na...

PurposeWe examined the impact of matrix food structure on post-prandial folate bioavailability (and other macronutrients) in human volunteers using a randomized, controlled, crossover experimental design.Methods Twelve healthy male volunteers (22.6 ± 0.4 years old) were offered four food models (differing in matrix structure: Custard, Pudding, Spon...

Background Since the early 1990s, major health and environmental concerns have developed and driven the emergence of diets involving a lower consumption of animal products. However, the transition towards greener diets is being hampered by the poor acceptance of vegan foodstuffs among western consumers. Mixed animal/plant alternatives to familiar d...

Background Egg white proteins (EWPs) are an excellent source of essential amino acids for human nutrition. Also, egg white is commonly used in food processing because of its numerous technological functionalities. Processing can influence the EWPs digestibility and thereby amino acid bioavailability. A better understanding of processing effects on...

The aim of the present study was to determine to what extent the food matrix could affect the release of docosahexaenoic acid (DHA) during digestion and its incorporation into systemic circulation. In this aim, three DHA-enriched egg products having the same composition but different structure were developed: omelet, hard-boiled egg, and mousse. Th...

The aim of this work was to investigate the role of biochemical digestion on softening and disintegration kinetics of pH 5 and pH 9 egg white gel (EWGs) during in vitro gastric digestion. EWG samples (5 mm length cubes) underwent in vitro digestion by incubation in simulated gastric fluid at different time intervals for up to 240 min. The hardness...

Salmonella enterica serovar Enteritidis is noted for its ability to survive the harsh antibacterial activity of egg white which is presumed to explain its occurrence as the major food-borne pathogen associated with the consumption of eggs and egg products. Liquid egg white is a major ingredient for the food industry but, because of its thermal frag...

Scope: The specific effect of the food matrix structure on fat-soluble micronutrient bioavailability is only partly understood. We aimed at evaluating fat-soluble micronutrient bioavailability in humans after consumption of foods displaying similar composition but different structure. Methods and results: Twelve healthy subjects were enrolled in...

The role of biochemical and mechanical disintegration on β-carotene release from steamed sweet potatoes (SSP) and fried sweet potatoes (FSP) during in vitro gastric digestion was investigated. Results revealed that, in the absence of mechanical forces generated by the stomach, biochemical digestion did not have a great effect on the breakdown of ce...

Salmonella Enteritidis is the most prevalent food-borne pathogen associated with egg-related outbreaks in the European Union. During egg colonization, S. Enteritidis must resist the powerful anti-bacterial activities of egg white (EW) and overcome ovotransferrin-imposed iron-restriction (the most important anti-bacterial mechanism of EW). Many path...

Infant formulas (IFs) are used as substitutes for human milk and are mostly based on cow milk proteins. For sustainability reasons, animal protein alternatives in food are increasingly being considered, as plant proteins offer interesting nutritional and functional benefits for the development of innovative IFs. This study aimed to assess how a par...

The fundamental mechanisms of nutrient release from solid foods during gastric digestion consists of multiple elementary processes. These include the diffusion of gastric juice into the food matrix and its simultaneous enzymatic degradation and mechanical breakdown by the peristaltic activity of the stomach. Understanding the relative role of these...

Digestion is a mechanical and chemical process that is only partly understood, and even less so for complex foods. In particular, the issue of the impact of food structure on the digestion process is still unresolved. In this study, the fate of four micronutrient-enriched foods with identical compositions but different microstructures (Custard, Pud...

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 structu...

This study investigated the feasibility of using hyperspectral imaging (HSI) to characterize the diffusion of acid and water within food structures during gastric digestion. Two different sweet potatoes (steamed and fried) and egg white gels (pH5 and pH9 EWGs) structures were exposed to in vitro gastric digestion before scanning by HSI. Afterward,...

Digestion behaviour of food protein-based hydrogels is greatly influenced by the gel characteristics and inparticular the microstructure. Using egg white gels (EWGs) as a model food, this study aimed to explore the realtime disintegration by pepsin of different microstructures and subsequent nutrient release kinetics. Usingthermal treatment at 80 °...

Salmonella enterica serovar Enteritidis (SE) is the most frequently-detected Salmonella in foodborne outbreaks in the European Union. Among such outbreaks, egg and egg products were identified as the most common vehicles of infection. Possibly, the major antibacterial property of egg white is iron restriction, which results from the presence of the...

Background Hen's egg food allergy is frequent in childhood and phenotypically heterogeneous. Some children can tolerate extensively heated egg. We investigated whether individual relative responses could differentiate children who tolerate baked egg. Methods Reactivities to raw, pasteurized or hard‐boiled egg (E), egg white (EW), and egg yolk (EY)...

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 p...

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 p...

The hypothesis is that the characteristics of ingested protein gels influences the subsequent in vivo gastric digestion process. Three egg white gels (EWGs) of identical composition but differing in structure and texture were prepared and fed to pigs. Sampling throughout a 6 h postprandial period, and at different locations in the stomach of the pi...

The present study investigated proteolysis combined with heat treatment to make hen Egg White (EW) anefficient emulsifier. EW was hydrolyzed by protease (Thermoase®) at various Enzyme Concentrations (EC) (w/w,0.1%, 0.2%, 0.4%, 0.8%), followed by heating at 90°C for 8 min. Results showed that optimal emulsifying abilityand stability, determined by m...

Due to intensive selection for many years and the genetic homogeneity of the strains of laying hens currently used, the average weight of a chicken egg varies little, ranging from 55 to 65 g. The egg consists of three main parts: the shell (about 10% of the weight of the egg), white or albumen (60%) and yolk or vitellus (30%).

Increasing bacterial resistance towards antibiotics has stimulated research for novel antimicrobials. Proteins acting on bacterial membranes could be a solution. Lysozyme has been proven active against E. coli by disruption of both outer and cytoplasmic membranes, with dry-heating increasing lysozyme activity. Dry-heated lysozyme (DH-L) is a mixtur...

Chicken egg white protects the embryo from bacterial invaders by presenting an assortment of antagonistic activities that combine together to both kill and inhibit growth. The key features of the egg white anti-bacterial system are iron restriction, high pH, antibacterial peptides and proteins, and viscosity. Salmonella enterica serovar Enteritidis...

Pasteurised liquid egg products represent around 70% of total egg products. Pasteurisation, necessary for microbiological safety, is a unit operation undergone by the totality of liquid whole egg commercialized. The present work aims to investigate the impact of a wide range of pasteurisation rates (among those classically used in industry) on the...

Egg white is a key ingredient in many food products as it combines high nutritional quality with excellent functional properties. However, it is also one of the leading causes of food allergy in childhood. Dehydrated egg white is a common form of industrial egg white. To increase the functional properties, egg white powders are heated which may cha...

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 l...

The aim of the present study was to understand to what extent the inclusion of anthocyanins into dairy and egg matrices could affect their stability after processing and their release and solubility during digestion. For this purpose, individual and total anthocyanin content of four different enriched matrices, namely custard dessert, milkshake, pa...

Chicken eggs are a multifunctional ingredient because, apart from their nutritional value, they can simultaneously serve several technological functions in a formulated food product. They are a universal ingredient in the home and food industry alike due to their emulsifying, foaming, gelling, thickening, coloring and aromatic properties. Numerous...

Par la qualité de ses protéines et lipides, et sa densité en vitamines et minéraux, l’œuf est un aliment de choix. Mais la consommation moyenne d’œuf en France est faible : entre 20 et 30 g/jour/personne, soit 3 à 4 œufs par semaine. Malgré sa forte densité nutritionnelle, l’œuf ne contribue donc que modestement aux apports nutritionnels observés (...

This study aimed to explore how food structure, in the form of different egg white gel matrices, impacts the peptide kinetics profiles using an in vitro model that simulated digestion in the adult gastrointestinal tract. Four different gel matrices were prepared by heating egg white gel solutions using different combinations of pH and ionic strengt...

Il est essentiel de trouver un équilibre entre la production d’aliments riches en nutriments et la préservation de l’environnement. Dans une perspective d’amélioration de la durabilité de notre système alimentaire, via potentiellement une plus grande place accordée à l’oeuf et aux ovoproduits, cette étude bibliographique vise à faire le point sur l...

The ability of egg white proteins to form gels with very different structures means that egg white has considerable potential as a functional food with controlled delivery properties. This work aimed to investigate the links between the gastric digestion process and the structural properties of three different egg white matrices. The heat-induced e...

Le comité d’organisation : Véronique Broussolle, UMR 408 SQPOV, INRA PACA Avignon Frédéric Carlin, UMR 408 SQPOV, INRA PACA Avignon Didier Lereclus, UMR 319 Micalis, INRA Jouy-en-Josas Christina Nielsen-Leroux, UMR 1319 Micalis, INRA Jouy-en-Josas Vincent Sanchis, UMR 1319 Micalis, INRA Jouy-en-Josas

The impact of dry heating on the progression of in vitro digestion of egg white proteins was investigated through application of multiple factor analysis (MFA) to electrophoresis data. Dry heating (from 1 to 10 days between 60 and 90°C) enhanced protein unfolding and aggregation, thus generating different SDS-PAGE patterns for each sample before di...

The ability of egg white proteins to form gels with very different structures means that egg white has considerable potential as a functional food with controlled delivery properties. This work aimed to investigate the links between the gastric digestion process and the structural properties of three different egg white matrices.The heat-induced eg...

Egg white is a common gelling ingredient that can produce gels with varying macro- and microstructures depending on the conditions (pH and/or ionic strength) employed, without the need to change the chemical composition. Consequently, egg white gels provide interesting models for investigating the food matrix effect on food digestion. In the presen...

Over the last decade, many studies have demonstrated the potential benefits of using anthocyanins (ACs) in the prevention of metabolic syndrome. Nevertheless, most of these studies have only considered ACs as pure compounds rather than ingredients of bioactive-enriched foods. However, the AC -food matrix interaction could deeply impact on its diges...

Docosahexaenoic acid (DHA) is an essential omega-3 polyunsaturated fatty acid (PUFA) which ingestion has positive effects on human health. Apart from being indispensable for the growth and functional development of the brain in infants and the maintenance of normal brain functions in adults, the intake of DHA would participate in preventing cardiov...

The last boundary between ingested food and the gastrointestinal (GI) tract mucosa is the mucus layer. This highly complex viscoelastic medium has evolved to provide a robust barrier that traps and immobilises potentially hazardous particulates such as bacteria but still allows the passage of nutrients to the epithelial surfaces. However, the rules...

Egg belongs to the list of ingredients that must be labeled because of its frequent involvement in food allergies especially in childhood. Several thermal processes are commonly applied to egg and it is known that some egg-allergic people can tolerate well-cooked egg. Food allergens are characterized by their ability to elicit IgE antibodies (sensi...

Lysozyme 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 orde...

Antimicrobial resistance is currently an important public health issue. The need for innovative antimicrobials is therefore growing. The ideal antimicrobial compound should limit antimicrobial resistance. Antimicrobial peptides or proteins such as hen egg white lysozymes are promising molecules that act on bacterial membranes. Hen egg white lysozym...

Maison de la Science en Bretagne Située sur le campus de Beaulieu de l'Université de Rennes 1, la Maison pour la science en Bretagne a ouvert ses portes en septembre 2014. Initiée par la Fondation "La main à la pâte" et par l’Académie des sciences, cette Maison est le fruit d’une collaboration exemplaire entre les universités, les grandes écoles br...

Antibiotic resistance causes public health problems and stimulates research for novelantimicrobials. Particular attention is given to molecules that limit drug resistancedevelopment.1Hen egg white lysozyme acting on the bacterial cell envelope through itsphysico-chemical properties is thus a good candidate.2,3However, its antimicrobial effectcaused...

Bacillus cereus group bacteria are opportunistically pathogenic spore-forming microorganisms well known in the sector of pasteurized food products because of their involvement in spoilage events. In the sector of egg product processing, these bacteria may lead to important economic losses. It seemed then relevant to study their behavior in egg whit...

The final boundary between digested food and the cells that take up nutrients in the small intestine is a protective layer of mucus. In this work, the microstructural organization and permeability of the intestinal mucus have been determined under conditions simulating those of infant and adult human small intestines. As a model, we used the mucus...

For food as well as for medical applications, there is a growing interest for novel and natural antimicrobial molecules. Lysozyme is a promising candidate for the development of such molecules. This protein is largely studied and known for its muramidase activity against Gram-positive bacteria, but it also shows antimicrobial activity against Gram-...

Des scientifiques rennais étudient les propriétés antibactériennes d’une protéine du blanc d’œuf.Battu en neige, il fait gonfler les gâteaux, et mousser le chocolat ! Mais le blanc d’œuf renferme d’autres secrets. Il contient notamment du lysozyme, une protéine qui lutte naturellement contre les bactéries. Cette action est connue depuis longtemps,...

Egg powders are used in many sectors of the food industry since they areeasy to handle in a safe manner, are not susceptible to bacterial growth, and canutilize precise water dosing in their formulation. Egg powders provide consumerswith advanced characteristics as well as technological advantages that are not foundin liquid egg products. To compet...

The last boundary between ingested food and the gastrointestinal (GI) tract mucosa is the mucus barrier. This highly complex viscoelastic medium has evolved to provide a robust barrier that can trap and immobilise potentially hazardous particulates such as bacteria but still allow the passage of nutrients to the epithelial surfaces (1,2). These con...

Food structure can have a major impact on digestion in the gastrointestinal tract. Moreover, the structure of food proteins, which are typically consumed within complex food matrices, can be modified during food processing. Protein aggregation is one such modification and in the present study, the relationship between thermally-induced aggregated s...

Antimicrobial drug resistance causes public health problems worldwide and stimulates research for novel antimicrobials.1 Particular attention is given to antimicrobial molecules that limit drug resistance development and have a large spectrum. Antimicrobial peptides and proteins are thus good candidates acting on the bacterial cell wall because of...

Assessing the nutritional quality of dietary proteins is important for formulating public health policies. Food processing technologies can modify protein structure and therefore can impact their gastrointestinal digestion, leading to different bioaccessibility outcomes. Heat-induced protein aggregation is a modification that commonly occurs during...

Natural preservatives answer the consumer demand for long shelf-life foods, considering synthetic molecules are perceived as a health risk. Lysozyme is already used because of its muramidase activity against Gram-positive bacteria. It is also described active against some Gram-negative bacteria; membrane disruption would be involved, but the mechan...

Bacterial membranes are often thought to be the main targets of the antimicrobial activity of egg white. In order to test this hypothesis, the state of the membranes of Escherichia coli K-12 cells during either bactericidal (45°C) or bacteriostatic (30°C) incubation in egg white at natural alkaline pH was studied by biochemical methods. Namely, the...

The hen's egg, in the form of table eggs and egg products, forms a staple part of the world's total protein consumption. In the last century, there has been considerable research effort focusing on ways of improving egg production and enhancing the quality of eggs. More recently, and with the development and application of new molecular technologie...

Research in the domain of antimicrobial molecules is nowadays a hot topic because of the increasing bacterial resistance against antibiotics; moreover, consumers demand for natural food preservatives is growing. Proteins and peptides from different origins, such as hen egg white lysozyme, seem promising candidates for the discovery of novel and nat...

Dietary proteins are believed to participate significantly in maintaining blood glucose levels, but their contribution to endogenous glucose production (EGP) remains unclear. We investigated this question using multiple stable isotopes. After overnight fasting, eight healthy volunteers received an intravenous infusion of [6,6-(2)H(2)]-glucose. Two...

Many food proteins as egg white or milk protein show tensioactive properties. This means that one region of the protein has affinity for polar environment and another region of the protein prefers an apolar environment. For that reason, these proteins tend to adsorb to amphiphilic-hydrophobic interfaces such as air-water interface of bubble surface...

Ovalbumin aggregation due to heating in solution increases its in vitro digestibility, compared to the native and dry-heated protein

The aim of this study was to produce intrinsically and uniformly doubly (15)N-(13)C-labeled proteins. These proteins can be used as intrinsic tracers of dietary amino acids, both α-amino groups and carbon skeletons, during postprandial metabolic utilization. Two (Rhodes) laying hens were fed for 16 days with a standard poultry diet supplemented wit...

Bioactive fractions of eggs for human and animal health

Identification of the key physicochemical parameters of proteins that determine their interfacial properties is still incomplete and represents a real stake challenge, especially for food proteins. Many studies have thus consisted in comparing the interfacial behavior of different proteins, but it is difficult to draw clear conclusions when the mol...