MucosAl pelliCle flAvouR interactiOn & perceptioN – MACARON

MACARON is a multidisciplinary project and its partnership combined expertise of (i) food chemistry and perception, biochemistry and analytical chemistry of proteins and aroma compounds from the team "Physique appliquée aux protéines" from l'Université Bourgogne Europe; (ii) cutting-edge microscopic techniques, including atomic force microscopy-based techniques, from the “Institute Carnot de Bourgogne” also belonging the Université Bourgogne Europe (P2) and (iv) tribology from the “Laboratoire de tribology et de dynamique des systèmes” at Ecole Centrale Lyon (P3) to explore hypotheses on the origin of astringency and solutions based on aroma to modulate its intensity.

The three partners of MACARON have co-published a perspective article presenting the new hypothesis studied in MACARON on the molecular origin of astringency. It allows us to share this hypothesis to the scientific community. This publication was the subject of a press release from INRAE. We have produced three new cell lines based on the TR146 cell line, which has been transfected with different MUC1 isoforms. They differ by i) the presence or not of the VNTR domain, which is highly glycosylated, ii) the cleavage or not of the two subunits and iii) the presence or not of a fluorescent marker (GFP) on the extracellular part of the protein. Using one of our cell lines, we have demonstrated that the mucosal pellicle increases the adsorption of aroma compounds at the cells’ surface and that aroma compounds are metabolized by the cells and human saliva depending on their structure. We have also shown that this metabolic activity occurs in vivo and that metabolized aroma compounds are less persistent than unmetabolized ones. This result has been published in food chemistry. We also publish a review in “Comprehensive Reviews in Food Science and Food Safety” describing enzymatic systems that may be involved in this metabolic activity and the potential impact on food perception.

MACARON will provide a breakthrough in the role of the oral mucosa in astringency and aroma persistence, which are two important modalities of flavour. The output of MACARON on the role of the MP in flavour perception, while considering multimodal integration of flavour, will enable new solutions for the development of food products to be proposed.

1. Carolina Muñoz-González, Marine Brule, Christophe Martin, Gilles Feron, Francis Canon. Molecular mechanisms of aroma persistence: From noncovalent interactions between aroma compounds and the oral mucosa to metabolization of aroma compounds by saliva and oral cells. Food Chemistry, Elsevier, 2022, 373 (Part B), pp.131467.
2. Mathieu Schwartz, Fabrice Neiers, Gilles Feron, Francis Canon. The Relationship Between Salivary Redox, Diet, and Food Flavor Perception. Frontiers in nutrition, Frontiers media, 2021, 7, pp.612735.
3. Mathieu Schwartz, F. Neiers, Jean-Philippe Charles, Jean-Marie Heydel, Carolina Muñoz-González, et al.. Oral enzymatic detoxification system: Insights obtained from proteome analysis to understand its potential impact on aroma metabolization. Comprehensive Reviews in Food Science and Food Safety, Wiley, 2021, 20 (6), pp.5516-5547.

MACARON addresses a new and fundamental question: the role of the oral mucosa (OM) in flavour perception (Axe 1.5, LS09, keywords: flavour and sensoriality). It also considers for the first time the role of MUC1, a tethered mucin expressed at the surface of the oral epithelial cells, in the structure and properties of the mucosal pellicle (MP) and flavour perception, focusing on astringency and aroma perception. MACARON takes the comprehension and characterization of astringency perception to new levels by exploring the current and new hypotheses of its molecular basis and by integrating both cross-molecular and cross-modal interactions with the aroma perception. Indeed, we propose that MUC1, as a signalling protein, is involved in the molecular mechanisms underpinning the perception of astringency via structural modifications (i.e., cleavage of its two subunits), initiating an intracellular calcium signal that leads to the release of neurotransmitters. We also suggest that the composition of the MP determines its properties and thus its ability to interact with aroma compounds and that the MP aggregation by astringent compounds impacts MP-aroma compound interactions. MACARON also considers the cerebral integration of these two multimodalities of flavour to understand how aroma and astringency perceptions impact each other.
These scientific questions are declined into 7 objectives that will be reach through a strategy based on the development of different experimental systems, including a model of the oral mucosa, protein models and a device for in vitro tribological experiments. This strategy results in a 4-year project divided into 4 main work packages (WPs), plus 1 WP dedicated to coordination and 1 WP dedicated to dissemination. This organization aims to compare in vitro and in vivo results to validate the model of the oral mucosa and to investigate flavour molecular mechanisms. MACARON is also a multidisciplinary project and its partnership combined expertise of (i) food chemistry and perception, biochemistry and analytical chemistry of proteins and aroma compounds from team 1 of the “Centre des Sciences du Goût et de l’Alimentation” (CSGA) (P1a); (ii) biochemistry, molecular biology and calcium imaging from the CSGA’s team 2 (P1b); (iii) cutting-edge microscopic techniques, including atomic force microscopy-based techniques, from the “Institute Carnot de Bourgogne” (P2) and (iv) tribology from the “Laboratoire de Tribology et de Dynamique des Systèmes” (P3) to explore hypotheses on the origin of astringency and solutions based on aroma to modulate its intensity. It is the first time that a project will merge these expertises to elucidate the molecular basis of astringency and will merge physic measurements of friction forces at the micro- and nanometric scales while considering for the first time the associated vibratory signal.
Thus, MACARON will provide a breakthrough in the role of the oral mucosa in astringency and aroma persistence, which are two important modalities of flavour. The output of MACARON on the role of the MP in flavour perception, while considering multimodal integration of flavour, will enable new solutions for the development of food products to be proposed.