Search

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 pigs, enabled a detailed spatial-temporal mapping of the pH, dry matter content, particle size and rheological properties. The results showed different gastric acidification kinetics implying an effect of the gel structure and/or texture. The most elastic and cohesive gel resulted in the highest median particle size and the most viscoelastic chyme. Distal and proximal regions of the stomach did not differ in terms of dry matter content, particle size distribution or rheological properties. These results demonstrate the consequences of protein food structure on gastric chyme properties, and thus suggest an effect on the digestion process.

This study aimed to perform Temporal Dominance of Sensations by modality (M-TDS) combined with a multi-intake approach to investigate texture and flavor perception in semi-solid products. Trained panelists (n = 15) evaluated fat-free strawberry yogurts enriched with functional proteins involving texture modifications. As yogurt is a semi-solid product, its in-mouth residence time is short. A multi-intake approach was therefore expected to give more reliable information about the sensory properties perceived by panelists. The two modalities of texture and flavor were analyzed separately to characterize the effect of added proteins. Trials were made according to an experimental design with two factors (protein type and concentration) and three levels each. Different statistical treatments, taking or not the temporality of attributes into account, were performed on standardized and non-standardized data. The implementation of M-TDS was essential to highlight differences of flavor perception in addition to the more evident texture modifications. The study of sensory trajectories evidenced that texture modifications, induced by the use of different whey proteins, slightly modified the perception of flavor and sweetness. The global flavor perception of the samples varied with the number of spoons, which particularly impacted the taste attributes. This study highlighted the importance of using M-TDS when studying texture and flavor in semi-solid products, and the relevance of the multi-intake approach to characterize flavor perception. This methodology enabled panelists to evidence both marked texture differences and subtler flavor modifications, and these useful data were emphasized by combining different statistical treatments.

National audience; La naturalité des produits alimentaires représente une demande forte des consommateurs des pays développés. La naturalité s’entend comme une réduction de l’emploi des additifs pour la fabrication, le stockage, la distribution ou l’usage des produits alimentaires, mais aussi la préservation des propriétés organoleptique et santé des macro- et micronutriments constitutifs. Les protéines sont des constituants essentiels pour texturer des aliments. Il existe cependant 2 limites à l’utilisation des protéines pour leurs propriétés de texture : une trop faible concentration en protéines ne permet pas de texturer une matrice alimentaire de façon satisfaisante, tandis qu’une trop forte concentration en protéines thermo-sensibles, comme les protéines de lactosérum, conduit à une agrégation excessive ou une gélification pendant leur traitement thermique. Un recours à l’addition d’agents gélifiants ou stabilisants est donc nécessaire pour atteindre la texture souhaitée (solide, visqueuse, fluide). Dans le cadre d’un projet interrégional, Profil, nous avons étudié le rôle de différentes fractions protéiques du lait pour contrôler la texture des émulsions sur une large gamme de concentration en protéines de lactosérum et sans ajout d’additif en combinant les propriétés de stabilité thermique des assemblages de protéines de lactosérum et les propriétés interfaciales des caséines. A teneur faible en protéines, notamment en caséines, les assemblages de protéines de lactosérum s’adsorbent à l’interface et connectent les globules gras, ce qui permet de texturer l’émulsion. A plus forte concentration en caséines, celles-ci couvrent l’interface au détriment des assemblages de protéines de lactosérum qui restent dans la phase dispersée et les émulsions sont fluides et stables après traitement thermique, même à forte concentration en protéines. Ces travaux ouvrent une voie innovante pour la création de produits laitiers sans additif répondant à la demande de naturalité des consommateurs. La compréhension du rôle de l’interface eau/huile dans la texturation des émulsions et son ingénierie constituent des leviers pour mieux contrôler la texture de produits existants. Ils offrent également des pistes pour la création de nouveaux produits correspondant à de nouveaux usages et de nouvelles habitudes de consommation. Les assemblages protéiques façonnés par traitements thermomécaniques permettent d’obtenir des propriétés fonctionnelles adaptées à un usage culinaire cible. Or, ces traitements impactent la structure des protéines et partie de leurs propriétés santé. Pour pleinement répondre aux enjeux de naturalité des produits alimentaires, la préservation des propriétés santé des protéines constitue également un enjeu majeur de l’alimentation de demain. Des pistes sont actuellement à l’étude pour répondre à ce double enjeu de maitrise de la techno-fonctionnalité et de la préservation de la bio-fonctionnalités des protéines.

Food is a complex combination of chemically diverse structures, influenced by composition andprocessing. The nutritional quality of food cannot be solely based on individual contents in nutrientsas food structure will strongly modulate the bioaccessibility of nutrients upon digestion. In previousstudies, the most common approach for measuring the extent of proteolysis and nutrient uptake wasto compare the initial macroscopic features of ingested food to final concentrations in thebloodstream. However, there is limited literature to the support underlying mechanisms of thedigestion of food in the stomach and enzyme diffusion in solid food substrates. In the present work,the influence of casein protein gel microstructure on enzymatic digestion was investigated for thefuture development of personalised foods. Casein gels with an identical composition, but differing bythe coagulation mode, were characterized and submitted to simulated gastric digestion. The changesin gel structure over time were studied using confocal microscopy and small angle x-ray scattering(SAXS). The molecular interactions that occur as a gel network is formed, and subsequently brokendown under digestive conditions will be discussed.

Comprendre la digestion pour proposer les aliments de demain. 1ère matinale thématique Sodiaal : la digestion, clé de l’innovation

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

Classiquement, la texture des desserts lactés à pH neutre, est obtenue grâce à des épaississants ou des gélifiants. Dans certaines conditions, des agrégats de protéines laitières sont également capables de connecter les gouttelettes de l’émulsion et de texturer le système. Au cours de ces travaux, nous avons étudié la capacité de différents agrégats à texturer des émulsions tout en faisant le lien avec leurs propriétés d’adsorption et d’étalement à l’interface dans un mélange complexe contenant aussi des protéines solubles. L’objectif était de contrôler la compétition d’adsorption entre ces différentes espèces et au final, la composition interfaciale, afin de maîtriser la texture des émulsions. Les résultats montrent la possibilité de texturer les émulsions pendant l’homogénéisation (gel instantané) mais également au cours du stockage (gel différé), et ce, même pour des teneurs en matière grasse faible.

National audience

Food is a complex combination of chemically diverse structures, influenced by composition and processing. The nutritional quality of food cannot be solely based on individual contents in nutrients as food structure will strongly modulate the bioaccessibility of nutrients upon digestion. In previous studies, the most common approach for measuring the extent of proteolysis and nutrient uptake was to compare the initial macroscopic features of ingested food to final concentrations in the bloodstream. However, there is limited literature to the support underlying mechanisms of the digestion of food in the stomach and enzyme diffusion in solid food substrates. In the present work, the influence of casein protein gel microstructure on enzymatic digestion was investigated for the future development of personalised foods. Casein gels with an identical composition, but differing by the coagulation mode, were characterized and submitted to simulated gastric digestion. The changes in gel structure over time were studied using confocal microscopy and small angle x-ray scattering (SAXS). The molecular interactions that occur as a gel network is formed, and subsequently broken down under digestive conditions will be discussed.

International audience; Animal-and plant-based proteins are present in a wide variety of raw and processed foods. They play an important role in determining the final structure of food matrices. Food proteins are diverse in terms of their biological origin, molecular structure, and supramolecular assembly. This diversity has led to segmented experimental studies that typically focus on one or two proteins but hinder a more general understanding of food protein structuring as a whole. In this review, we propose a unified view of how soft-matter physics can be used to control food protein assembly. We discuss physical models from polymer and colloidal science that best describe and predict the phase behavior of proteins. We explore the occurrence of phase transitions along two axes: increasing protein concentration and increasing molecular attraction. This review provides new perspectives on the link between the interactions, phase transitions, and assembly of proteins that can help in designing new food products and innovative food processing operations.

Beyond nutrient composition matrix plays an important role on food health potential, notably acting on the kinetics of nutrient release, and finally on their bioavailability. This is particularly true for dairy products that present both solid (cheeses), semi-solid (yogurts) and liquid (milks) matrices. The main objective of this narrative review has been to synthesize available data in relation with the impact of physical structure of main dairy matrices on nutrient bio-accessibility, bioavailability and metabolic effects, in vitro, in animals and in humans. Focus has been made on dairy nutrients the most studied, i.e., proteins, lipids and calcium. Data collected show different kinetics of bioavailability of amino acids, fatty acids and calcium according to the physicochemical parameters of these matrices, including compactness, hardness, elasticity, protein/lipid ratio, P/Ca ratio, effect of ferments, size of fat globules, and possibly other qualitative parameters yet to be discovered. This could be of great interest for the development of innovative dairy products for older populations, sometimes in protein denutrition or with poor dentition, involving the development of dairy matrices with optimized metabolic effects by playing on gastric retention time and thus on the kinetics of release of the amino acids within bloodstream.

The timely complementary food introduction is important for the development of healthy eating. However, little evidence is available about when to introduce which texture during this period. This study aims to fill this gap by measuring the evolution of food texture acceptance and feeding behaviours between 6 and 18 months. Two groups of healthy children participated in the study: at 6, 8, and 10 months (n=24) and at 12, 15 and 18 months (n=25), respectively. They were offered foods with different textures (purees, double textures, cooked pieces, sticky and hard foods) at an age when few infants were already familiar with these textures. For each food texture, children’s acceptance (ability to process and swallow a food) and feeding behaviours (sucking and chewing) were assessed by the investigator; liking was assessed by parents. At 6 months, pureed and double textures were highly accepted (Acceptance Probability AP>0.8); when offered at 8 months, cooked pieces were highly accepted (AP>0.8). Up to 10 months, the acceptance of more complex textures (e.g. cheese, bread crust) increased strongly with age as did chewing behaviour. At 12 months, most food textures were accepted (AP>0.5), except raw vegetable pieces and pasta (AP0.5 at 18 months. In conclusion, children accepted most textures at an earlier age than their parents’ feeding practices; their feeding behaviours depended on age and food texture and acceptance of hard textures was related to the development of chewing.

Après avoir présenté rapidement le projet PROFIL et plus particulièrement l’axe « propriétés detexture », les auteurs décrivent la problématique qui consiste à produire des assemblages fonctionnels deprotéines du lactosérum par chauffage. Une alternative au chauffage de solutions de protéines a étéexploitée, l’étuvage, qui consiste à chauffer la poudre de protéines à un couple temps-température et uneactivité d’eau (aw) définis. Ce procédé de chauffage est largement utilisé pour les ovo-produits afinaugmenter leur fonctionnalités (propriétés moussantes et gélifiantes), mais pas ou peu pour les protéinesde lait.Un procédé pour produire des assemblages de protéines du lactosérum par étuvage est ensuitedécrit, qui consiste à ajuster une solution de protéines du lactosérum à un pH alcalin, à la sécher, puis àétuver la poudre à une température > 100°C pendant une quarantaine d’heures. Des assemblagesparticulaires possédant une taille et une forme proches de la taille et de la forme de la poudre étuvée sontainsi produits, c’est-à-dire que la particule de poudre est insolubilisée par le procédé d’étuvage. Comme lapoudre comprend beaucoup d’air et que cet air est remplacé par l’eau au moment de la mise ensuspension dans l’eau de la poudre, les particules formées complexent de très fortes quantités d’eau etexpriment de fortes viscosités en suspension pure.L’optimisation du procédé, qui a permis de réduire les temps d’étuvage à moins d’une heure, estensuite présentée, ainsi que les applications potentielles de ces assemblages comme ingrédients dans lesproduits alimentaires.

International audience

The αs1-casein hydrolysis has been shown to greatly influence the texture and techno-functionalities of hard cooked cheeses. This hydrolysis can be performed by the proteinases of the thermophilic lactobacilli since rennet, also implied, is denatured during the cooking step. However, it is unclear whether these changes are only due to the proteolytic activity of lactobacilli, the pH decrease in cheese or both. Small scale Swiss-cheeses were made from microfiltered milk using various combinations of starters including or not lactobacilli: i) Streptoccocus thermophilus alone (STH cheeses), ii), S. thermophilus in enriched lactose cheesemilk (STH-LACT cheeses) to reach pH level similar to cheese with lactobacilli and iii) S. thermophilus and lactobacilli either L helveticus (STH/LH cheeses), or L. delbrueckii subsp lactis (STH/LL cheeses). As S. thermophilus does not metabolize the galactose moiety of lactose, the pH at day 1 of these STH-LACT cheeses was similar to those made with lactobacilli (pH 5.15-5.25) while pH values of the STH cheeses were higher (pH 5.40). Higher firmness and chewiness of the melted ripened STH cheeses were correlated with a higher pH at day 1 and with a lower proteolysis (twofold amount of remaining intact αs1-casein) compared to the STH-LACT cheeses as well as the cheeses with lactobacilli. Conversely, the stretchability showed different behaviors depending both on the quantitative and qualitative proteolysis and on the pH value. The lower pH and content in small peptides led to higher stretchability of the STH-LACT and STH/LH cheeses in contrast to the cheeses STH (high pH and few small peptides) and STH/LL (low pH and high amount of small peptides). In conclusion, the decrease in pH due to the use of lactobacilli plays a key role in the texture of raw and melted Swiss-cheese. Beside the pH, the proteolytic activity of lactobacilli is also a determinant factor for stretchability.

The acceptability of foods by consumers is mainly driven by its overall perception, including texture, taste and aroma. As food is put in the mouth, food breakdown contributes to the different sensory perceptions until swallowing and the amount of product remaining in the mouth after swallowing contributes to after-feel perception. Food texture depends on food composition and structure but also on oral physiological parameters which vary according to the individuals and impact food bolus structure. Food texture also impacts taste and aroma perception. In fact, a modification of food composition and structure does not only affect texture perception but also aroma and taste perception due to a modification of the release of taste and aroma stimuli. Moreover sensory interactions occur between texture and both taste and aroma sensory perception. The aim of this presentation is to present the effect of food texture on the global sensory perception in dairy products, taking into account food composition (fat, protein, dry matter, ions, texture replacers) and food structure on one hand and human physiological parameters (masticatory behaviour, saliva flow and composition, oral volume, respiratory flow) on the other hand. Examples will be given on semi-hard dairy product which are chewable and for which mastication and salivation play an important role and on different types of dairy emulsions for which tongue-palate compression, melting and saliva composition are more important. Another focus will be done on fat perception, a multimodal perception involving texture, taste and aroma.

International audience; Gastric emptying of food is mainly driven by the caloric concentration, the rheological properties of the chyme, and the physical state (liquid/solid) of food once in the stomach. The present work investigated: (1) The effect of the composition and the viscosity of drinkable yogurts on gastric emptying in pigs, and (2) the behavior of yogurts during dynamic in vitro digestion. Three isocaloric liquid yogurts were manufactured: Two enriched in protein and fiber showing either a low (LV) or high (HV) viscosity, one control enriched in sugar and starch (CT). They were labelled with 99mTc-sulfur colloid and given to pigs (n = 11) to determine gastric emptying pattern by gamma scintigraphy. Then dynamic in vitro digestion of the yogurts was done using the parameters of gastric emptying determined in vivo. Gastric emptying half-times were significantly longer for LV than CT, whereas HV exhibited an intermediate behavior. In vitro gastric digestion showed a quick hydrolysis of caseins, whereas whey proteins were more resistant in the stomach particularly for LV and HV. During the intestinal phase, both whey proteins and caseins were almost fully hydrolyzed. Viscosity was shown to affect the behavior of yogurt in the small intestine.

The elderly population is growing increasingly. In 2030, 1/3 of the population will be over 60 years old. However this population has specific nutritional needs and often, oral impairments such as loss of tooth and/or decrease of salivary flow. Therefore it is necessary to develop foods adapted for the elderly, in terms of organoleptic properties and nutritional composition. In this context, the purpose of this work is to study the impact of oral impairments of elderly persons on food comfortability and bolus properties during the consumption of dairy products.76 elderly persons (ages 66 to 88, 42 women and 34 men), with or without oral health problems in terms of dental and/or salivary status were recruited. Four dairy products with identical composition but different textures (soft, hard, pasty and dry) were studied. Food comfortability of the four dairy products was assessed by means of a questionnaire based on bolus formation, pain, and texture and flavor perception. The time and number of cycle required to form the bolus for elderly person consuming each product was measured (video) as rheological properties (compression test) and saliva incorporated (dry extract) in each bolus. Statistical analysis (correlation, ANOVA, multiblock analysis) of the data were performed.Despite a wide array of texture, dairy products were comfortable for the elderly whatever their oral health. According to the food comfortability questionnaire, neither bolus formation, nor pain or organoleptic properties were significantly affected by the dental and/or salivary status of the elderly. The stimulated saliva flow was positively correlated with the amount of saliva incorporated in the bolus. Moreover dental status was correlated with the hardness of the bolus and results suggested that the dental status slightly affected the texture perception.Finally, food comfortability of our products was not affected by the oral health contrary to the bolus properties.

Food structure affects the kinetics of food digestion and the bioavailability of nutrients. Rencontre Université de Suzhou et industriels chinois COFCO

Gastric digestion of food is the result of physical disintegration and enzymatic reactions leading to the release of nutrients. Depending on the gelation conditions, food protein networks with specific structural and rheological features can be formed. Several in vivo and in vitro studies have shown an influence of the macro- and microstructure on the kinetics of milk protein hydrolysis. Despite growing interest to modulate food structure to potentially control digestion rates, little is known concerning the fundamental mechanisms by which the structure of dairy gels affects the digestion kinetics.An original time-lapse synchrotron deep-UV microscopy method was developed using the natural tryptophan fluorescence of proteins. It allowed monitoring in situ the microstructural evolution of protein gels during simulated gastric digestion. Two dairy gels of identical composition but different coagulation modes (acid and rennet) were submitted to static in vitro digestion with the aim of decoupling the acidification process from the enzymatic action of pepsin. Automated analysis procedures of the collected images allowed to model the kinetics of disintegration of sub-millimetric gel pieces. Results confirmed the propensity of rennet gels, but not acid gels, to undergo large microstructural modifications and form compact protein aggregates (syneresis) under acidic conditions. Consequently, the kinetics of proteolysis was much slower for the rennet gel, reiterating the hypothesis of a pepsin accessibility reduced to the surface of solid casein substrates (Fig 1). Finally, the morphological shapes of particles were almost preserved during the full digestion process and the kinetics of disintegration could be fitted by a simple exponential model. Therefore, we concluded that the erosion mode is probably the predominant mechanism during the gastric digestion of dairy gels.

The elderly population is growing increasingly. In 2030, 1/3 of the population will be over 60 years old. However this population has specific nutritional needs and often, oral impairments such as loss of tooth and/or decrease of salivary flow. Therefore it is necessary to develop foods adapted for the elderly, in terms of organoleptic properties and nutritional composition. In this context, the purpose of this work is to study the impact of oral impairments of elderly persons on food comfortability and bolus properties during the consumption of dairy products.76 elderly persons (ages 66 to 88, 42 women and 34 men), with or without oral health problems in terms of dental and/or salivary status were recruited. Four dairy products with identical composition but different textures (soft, hard, pasty and dry) were studied. Food comfortability of the four dairy products was assessed by means of a questionnaire based on bolus formation, pain, texture and flavor perception. The time and number of cycle required to form the bolus for elderly person consuming each product was measured (video) as rheological properties (compression test) and saliva incorporated (dry extract) in each bolus. Statistical analysis (correlation, ANOVA, MFA) of the data were performed.Despite a wide array of texture, dairy products were comfortable for the elderly whatever their oral health. According to the food comfortability questionnaire, neither bolus formation, nor pain or organoleptic properties were significantly affected by the dental and/or salivary status of the elderly. The stimulated saliva flow was positively correlated with the amount of saliva incorporated in the bolus. Moreover dental status was correlated with the hardness of the bolus and results suggested that the dental status affected also the texture perception.Finally, food comfortability of our products was not affected by the oral health contrary to the bolus properties.

Food structure is an important factor in the nutritional quality of foods. With regard to dietary protein, it may have an impact on protein digestibility, proteolysis kinetics, gastric emptying and amino acid bioavailability, all with potential metabolic consequences. Egg white is an appropriate food model to investigate these issues, since very different structures and textures can be produced while keeping the chemical composition constant. Recently, we established that protein matrix structure impacts the extent of proteolysis and the nature ofthe peptides generated during in vitro digestion of egg white protein aggregates and gels. Our question here is “do such differences also exist in vivo, and do they have any biological consequences?” To address these questions, a smooth-rigid egg white gel, a granular-spongy gel and an intermediate gel were prepared. Each gel was fed to pigs (n=33) as a single meal, and gastric chyme samples were collected over a 6h-postprandial period in order to measure pH, proteolysis and particle size along digestion at 10 different stomach locations. Blood samples were also collected for plasma amino acid analyses.Acidification of the chyme started in the pylorus regin regardless of the type of gel, but acidification kinetics depended on the gel type, which suggested that gel structure impacts on HCl distribution in the chyme. In contrast, proteolysis commenced in the proximal region, consistent with the location of pepsinogen secretory cells. But from 1h-postprandial, proteolysis profiles greatly differed depending on the gels: the higher proteolysis was 2 observed in the pyloric region for the granular-spongy gel (acidity and proteolysis gradients were consistent), while maximum proteolysis was observed in the proximal region for the smooth-rigid and intermediate gels (acidity and proteolysis gradients were opposite), suggesting that pepsin diffusion profiles depend on the type of gel. Proteolysis kinetics weremore rapid with granular-spongy gel than with intermediate gel, while the smooth-rigid gel was the most resistant to proteolysis, which was consistent with the particle size observed during digestion. Finally, amino acid absorption was faster for the granular-spongy gel than for the two other gels.

International audience; From their amphiphilic nature, proteins in solution adsorb spontaneously at hydrophobic interfaces. Proteins are thus able to change their conformation, which modifies their surface properties. In the confined space near the interface, these modifications favor the formation of many interactions of weak energy (hydrophobic interactions, hydrogen bonds, Van der Waals interactions), and thus the creation, in the interface plane, of a network of intermolecular interactions. Adsorbed proteins can thus, in favorable conditions, constitute at the interface a continuous film with visco-elastic properties. These mechanical properties contribute to the stabilization of the interface created in multiphasic systems such as foams. Our work focuses on the behavior at the air-water interface and, if needed the foam properties, of some model globular proteins: ovalbumin, lysozyme, ovotransferrin, β-lactoglobulin… The aim of our work is to understand, using these models, how protein properties (structure, biochemistry, physico-chemistry), potentially adjusted by the physico-chemical environment, chemical changes or thermo-mechanical treatments, take part in the interfacial behavior, film characteristics and macroscopic proprieties of foams (overrun, stability, texture). Besides, in systems where several proteins with different properties (size, hydrophobicity, charge, conformation flexibility,…) coexist, we look to understand how the interactions between proteins enhance behaviors that cannot be considered as the sum of the single behaviors. The issue over time is to control technological parameters to improve texture properties in relation to foaming capacity.

The weaning period is a transition from milk to family foods and is a critical phase for the development of food acceptance and eating habits of children. The texture of the complementary food introduced plays an important role in shaping preferences. It is known that early introduction of solid food and experience in difficult-to-chew textures could enhance later food acceptance. Texture acceptance follows the developmental sequence of oral functions and infants are more likely to accept texture they can manipulate in mouth. The development of these functions (mainly chewing) is thought to depend on the texture infants are exposed to. Infant refusing foods that require significant chewing may fall behind in their oral motor development as a result of lack of experience with chewing. Moreover hard, fibrous, non-softened foods are thought to be the only foods able to encourage enough mastication to allow growing of dental arches. WHO guidelines recommend to start weaning at 6 months and to gradually increase food consistency as infants get older. A critical window for introducing lumpy food is also suggested (not beyond 10 months) to avoid feeding difficulties later on. Presently, ready-to-eat foods are an important part of weaning foods in most of the developing and developed countries. These commercial preparations meet nutritional needs at different age groups. Nevertheless, there is limited information available on the texture of these commercial preparations. The objective of this study was to characterise the structural properties of baby foods and to describe how these properties change as children grow. We selected 7 fruit purees, 18 savoury baby-foods and 4 biscuits, representing products proposed on the French market for 4/6 months to 24 months old children by three main baby-food manufacturers. Pureed products were characterised by their flow behaviour. All samples exhibited shear-thinning behaviour. Thixotropic behaviours were observed for samples containing banana and biscuits only. Significant differences in apparent viscosity (50 s-1) were observed between recipes but they were not related to age-group. Savoury foods were vegetable purees (4-6 months) which included particles (mainly carrots and pasta) from 8 months onwards. Particles were weighted and their size was determined by image analysis. Particles represented 12 to 49 % of product total weight and measured between 3 to 20 mm. The quantity and the size of the particles increased with age, but large variations were observed between brands and between recipes. The hardness of these particles is under investigation using extrusion method. Finally, experiments are currently ongoing to determine the physical (density, humidity) and rheological (3-point bending test and compression tests after short immersion in water/ saliva) properties of the cereal products.

Vitamine A, oméga 3, polyphénols ... Des chercheurs explorent de nouvelles pistes pour améliorer l'alimentation des seniors et leur permettre de rester en bonne santé le plus longtemps possible.

Cheese flavour has been widely studied and key-aroma compounds identified. However the strategies involved were mostly correlation studies between quantitative measurements of aroma compounds and either gas chromatography olfactometry (GC-O) data or sensory data. These correlations do not take in account the differences in the Stevens’ slopes relating sensory perception and concentration and perception thresholds. The objective of this study was thus to explain sensory perception of cheese by the intensity of single molecules measured by GC-O analysis. Seven commercial semi-hard cheeses were evaluated by a sensory descriptive analysis. Thirteen odour attributes were evaluated by a panel of trained judges. The volatile compounds of the cheeses were then extracted by dynamic headspace and the odour active compounds were detected by GC-O by eight trained judges applying the Osme technique which accounts for Stevens’ slopes. The odour active compounds were then identified by a two-dimensional GC-heartcut procedure (GC-GC-MS/O). Finally the intensity scores for the sensory attributes and for the odour-active compounds were analysed by partial least squares (PLS) to find correlations between the two datasets. The PLS showed strong correlations between the sensory attributes and the odour active compounds, for example the buttery attribute evaluated by the sensory profile were strongly correlated with 2,3-butanedione and 3-hydroxy-2-butanone known for their buttery odours and the cheesy sensory attributes were very well correlated with butanoic acid and isovaleric acid known for their cheesy odours. This correlation study has given us great opportunities to apprehend sensory attributes when accounting for Steven’s Power Law and perceptions thresholds of odour active compounds. However, a limit of GC-O analysis is to not accounted for perceptual interactions such as masking and synergy among odorants. This will be further investigated by omission experiments.