Food oral processing and chewing mechanisms in the elderly : applied to the development of soft cereal foods fortified with proteins

Afin de développer des aliments adaptés aux populations seniors, dans le cadre du projet ANR-AlimaSSenS, l’objectif de cette thèse a été de comprendre les mécanismes de destructuration et de formation du bol alimentaire de deux aliments céréaliers (brioche et génoise) enrichis en protéines de légumineuses. La déstructuration orale de ces aliments (FOP) a été étudiée par imagerie et par rhéologie, en lien avec la perception du confort en bouche et la physiologie des seniors. Il a été montré que le flux salivaire a une influence majeure sur la viscosité du bol alimentaire, elle-même fortement liée à la perception du confort. La fragmentation de l’aliment dépend de sa texture et de l’état dentaire du sujet. Afin de préciser ces relations, l’évolution des propriétés mécaniques et de la structure alvéolaire des aliments lors de la mastication a été étudiée par microtomographie aux rayons X sous compression in situ, en grandes déformations (90%). Les résultats, qui s’appuient sur une modélisation par éléments finis, montrent que l’épaisseur et l’hétérogénéité des parois jouent un rôle clé dans les mécanismes de fragmentation. Finalement, l’impact de l’enrichissement sur la texture dépend du produit, et modifie les mécanismes de destructuration orale et de perception du confort. Pour la génoise, cet impact peut être minimisé par le procédé, tout en préservant la digestibilité des protéines. Cette étude interdisciplinaire débouche donc sur des propositions concrètes pour élaborer des aliments céréaliers réalistes, aux propriétés sensorielles acceptables et contribuant à satisfaire les besoins nutritionnels des seniors.The oral physiology of the elderly isgenerally altered and their protein needs are higherthan adults. In order to develop foods that are fit forthis population, within the framework of the ANRAlimaSSenSproject, the aim of this thesis was tounderstand oral breakdown and bolus formationmechanisms of two soft cereal foods (brioche andsponge cake) fortified with pulse proteins. The oralprocessing of these foods (FOP) was studied byimaging and rheology, and results related to theperception of oral comfort and the physiology of theelderly. Salivary flow was found to have a majorinfluence on the viscosity of the bolus, the latterbeing strongly related to the perception of comfort.Food fragmentation depended on the texture of thefoods and on the individual’s dental status.To clarify these relationships, the evolution of themechanical and structural properties of thematrices was studied by in situ X-raymicrotomography under compression at large deformations (90%). Results, confirmed by finite element numerical modeling, showed that the cell wall thickness and heterogeneity play a key role in the fragmentation mechanisms. Finally, the impact of protein fortification on the texture depends on the product, and reflects on the mechanisms of oral processing and oral comfort perception. In sponge-cake, these changes can be minimized via the processing, while preserving the digestibility of proteins. This interdisciplinary study leads to concrete proposals for developing realistic cereal foods, with acceptable sensory properties and helping to meet the nutritional needs of seniors

Guiding the formulation of soft cereal foods for the elderly population through food oral processing: Challenges and opportunities

International audienceAs the elderly population is growing steadily, more age-friendly food products that allow them to cover their nutritional needs and are enjoyable need to be designed. Since their oral physiology is considerably altered, the study of Food Oral Processing has become an essential discipline in food development, as it takes into consideration the complex interactions between food structure, oral processing, physiology and perception. Cereals are staple foods in many countries, and their consumption as bakery products is popular among the elderly population. In addition, when fortified with pulse proteins, they can help meet the protein needs of seniors and help fight against sarcopenia. For these reasons, this chapter presents an overview of the various aspects involved in the oral processing and formulation of soft cereal foods, translating them into challenges and opportunities that are of relevance to the design of realistic soft cereal foods targeted for the elderly that are nutritious and sensory appealing. This review focuses on the healthy elderly population and does not intend to cover the needs of the dependent elderly suffering from chronical diseases

Relationships of oral comfort perception and bolus properties in the elderly with salivary flow rate and oral health status for two soft cereal foods

International audienceThe aim of this study was to investigate food oral processing and bolus formation in the elderly population, and their relationship with the perception of oral comfort, for two soft cereal products of different composition: sponge-cake and brioche. Twenty subjects aged 65 and over participated in the study. They were classified in two groups according to dental status (poor vs. satisfactory) and presented various stimulated salivary flow rate (SSF) in each group. Food bolus properties (hydration ratio and apparent viscosity) were characterized after three chewing stages for both groups. Results showed that chewing duration did not depend on food product but rather on physiology: subjects with a poor dental status had a shorter chewing duration. For each chewing stage, sponge-cake boli showed a higher hydration ratio than brioche boli, which showed higher apparent viscosity. For sponge-cake, perception of oral comfort was primarily driven by SSF rate, irrespective of the dental status. In the case of brioche, oral comfort was also partially explained by SSF in the case of subjects with poor dental status. This result suggests that perception of oral comfort in brioche could be driven by product related attributes rather than oral health. For both foods, a phenomenological model of bolus viscosity as a function of stimulated salivary flow and chewing duration was proposed

Role of the bolus degree of structure on the protein digestibility during in vitro digestion of a pea protein fortified sponge-cake chewed by elderly

International audienceThis study investigated the digestibility of proteins in a pea protein fortified sponge-cake, as well as the impact of the degree of structure of the bolus produced by elderly subjects on the digestibility of proteins by combining ex vivo and in vitro approaches via the standardized protocol INFOGEST. The sponge-cakes were consumed by a group of 20 elderly subjects with contrasting physiology, their boli were recovered just before swallowing, and their apparent viscosity was measured to delineate the bolus degree of structure. According to this criterion, two pools were formed with boli from subjects selected at the extremes: low viscosity (LV) and high viscosity (HV), with apparent viscosity values (at 120s(-1) ) of 124 +/- 18 Pas and 208 +/- 19 Pas, respectively. The sponge-cakes and the two pools underwent in vitro digestion. Protein hydrolysis kinetics was followed by measuring the released primary amino groups (NH2 ) and by SDS-PAGE at different time points. For all samples, the representative bands of pea proteins disappear gradually during digestion, accompanied by the appearance of bands indicating the presence of proteins with MW < 15kDa. In addition, the NH2 concentrations increase over time and do not differ between sponge-cake and pea protein isolate. Moreover, the degree of structure of the food bolus has no significant effect on the concentration of NH2 released. These results showed that pea proteins in a fortified sponge-cake are bioaccessible under standardized conditions, and that the degree of structure of the bolus did not influence protein digestibility for these foods

Fragmentation of two soft cereal products during oral processing in the elderly: Impact of product properties and oral health status

International audienceThis study investigated the mechanisms of fragmentation leading to bolus formation during chewing in the elderly population for two cereal foods of different compositions and cellular structure: sponge-cake (SC) and brioche (B). For both products, mechanical properties were characterized by uniaxial compression and 3D cellular structure was determined using x-ray micro-tomography. Stress-strain curves showed two distinct ductile-like behaviors: product B underwent plastic deformation, whereas product SC displayed a hyper-elastic behavior. Twenty subjects aged 65 years and over with two different oral health conditions (poor vs satisfactory dental status, variable stimulated salivary flow rate) were asked to consume both products. Bolus particle size was determined at three different chewing stages through image analysis, and the resulting particle size distribution (PSD) curves were fitted by Gompertz model. The model parameters were related to bolus particle heterogeneity and fragmentation, thanks to their correlations with median particle size diameter D-50 and interquartile ratio (D-75/D-25), directly extracted from PSD curves. The use of model parameters allowed discriminating between chewing sequences for both products and revealed different fragmentation patterns: while SC boli exhibited a continuous particle size reduction during chewing, B displayed a combination of fragmentation and agglomeration. In addition, results showed that subjects with a satisfactory dental status produced significantly more degraded boli than those with a poor dental status. These results highlight distinct fragmentation mechanisms for these two soft products that were interpreted in relation to their differences in composition, structure and mechanical behavior

Impact de l’incorporation en protéines de légumineuses (pois et fève) dans des produits céréaliers (brioche et génoise) à destination de personnes âgées sur la transformation orale et la digestibilité in vitro des protéines

International audienceThe objective of this work was to understand, in the elderly, the mechanisms of oral breakdown and bolus formation for two cereal foods (brioche and sponge cake) enriched with pulse proteins (pea and faba bean), in order to develop foods acceptable for the elderly population. The food oral processing (FOP) of these two food products has been studied by imaging and rheology, in connection with the perception of in-mouth comfort and with the oral physiology of seniors. It has been shown that the salivary flow has a major influence on the viscosity of the food bolus, which is itself strongly linked to the perception of comfort for non enriched products. The impact of enrichment on texture depends on the product considered. It modifies the mechanisms of FOP and perception of oral comfort. For sponge cake, this impact can be reduced by adapting the process, with apparently, small impact on protein digestibility evaluated in vitro. This interdisciplinary study therefore leads to recommendations for developing realistic cereal foods, with acceptable sensory properties and meeting the elderly people's nutritional needs

Assessment of the interactions between pea and salivary proteins in aqueous dispersions

To understand and limit the unpleasant oral sensation of astringency felt during the consumption of pea-based drinks, we investigated the interaction between mixtures of salivary and pea proteins, as compared to mixtures where HEPES buffer (at pH 6.8) was used as a negative control for saliva. Since astringent compounds have the ability to bind with salivary proteins, mixes of freshly collected whole unstimulated saliva and a pea protein isolate (PPI) (a dispersion at 3.5% w/v) were prepared in ratios 95:5 and 1:1 saliva:PPI, to allow different stoichiometries to occur in the mouth. Samples were incubated at 37 °C during 30 min, after centrifugation at 16000g during 20 min to separate pellet from supernatant. Using techniques such as SEC, Native-PAGE and LC-MS, 7 pea proteins were identified as being capable of forming aggregates with at least 7 saliva proteins, some of which have been previously connected to astringency