Maud Panouillé

Respective impact of bread structure and oral processing on dynamic texture perceptions through statistical multiblock analysis

Texture perception is a multidimensional and dynamic phenomenon resulting from both the initial structure of food and its breakdown during oral processing. The aim of this study is to identify the respective contribution of food and bolus properties to temporal changes in texture perceptions during bread consumption. For this purpose, the perception dynamics of three French baguettes with different structures were assessed through Temporal Dominance of Sensations and Progressive Profiling. Samples of crumb with and without crust were tasted by trained panelists. The intensities of nine texture attributes were evaluated at three key stages of oral processing (10%, 40% and 100% of individual swallowing time) using the Progressive Profiling method. Six of them were related with a Multiblock Partial Least Squares (MB-PLS) regression to the initial bread properties and to some bolus properties measured at these three stages. The evolution during oral processing of some attributes such as soft, dry, doughy and sticky was more influenced by modifications of bolus properties than by the initial characteristics of the breads. Among bolus properties, the MB-PLS highlighted that the hydration and texture properties of the bolus had a greater impact on texture perceptions than bolus structure. The aerated perception was more affected by the crumb structure, while the heterogeneousness and the crispiness were more affected by the presence of crust. This study thus contributes to improving our understanding of dynamic texture perceptions through a statistical model that takes the physical properties of bread and bolus during oral processing into account.

Exploring the breakdown of dairy protein gels during in vitro gastric digestion using time-lapse synchrotron deep-UV fluorescence microscopy

A novel time-lapse synchrotron deep-UV microscopy methodology was developed that made use of the natural tryptophan fluorescence of proteins. It enabled the monitoring in situ of the microstructural changes of protein gels during simulated gastric digestion. Two dairy gels with an identical composition, but differing by the coagulation mode, were submitted to static in vitro gastric digestion. The kinetics of gel particle breakdown were quantified by image analysis and physico-chemical analyses of digesta. The results confirm the tendency of rennet gels, but not acid gels, to form compact protein aggregates under acidic conditions of the stomach. Consequently, the kinetics of proteolysis were much slower for the rennet gel, confirming the hypothesis of a reduced pepsin accessibility to its substrate. The particle shapes remained unchanged and the disintegration kinetics followed an exponential trend, suggesting that erosion was the predominant mechanism of the enzymatic breakdown of dairy gels in these experimental conditions.

Gaining deeper insight into aroma perception: An integrative study of the oral processing of breads with different structures

The objective of this study was to investigate for the first time the influence of bread structure, volatile compounds, and oral processing on aroma perception. 3 types of French baguette were created using the same raw ingredients but different bread-making processes; they consequently varied in their crumb and crust structures. We characterized the initial volatile profiles of two bread structural subtypes-namely bread crumb and bread crumb with crust-using proton transfer reaction-mass spectrometry (PTR-MS) headspace analysis. Three types of bread were characterized by thirty-nine ion fragments from m/z 45 to 139. We then conducted a study in which 8 participants scored aroma attribute intensities for the different bread types and subtypes at 3 key stages of oral processing (10, 40, and 100% of individual swallowing time). At these 3 time points, we collected boli from the participants and characterized their volatile profiles using PTR-MS headspace analysis. The results suggest saliva addition dilutes volatile compounds, reducing volatile release during oral processing. Thus, a bread with high porosity and high hydration capacity was characterized by a low volatile release above boli. We examined the relationships between 4 aroma attributes of bread crumb with crust and 24 discriminatory fragment ions found in boli headspace. This study demonstrated for the first time that the perceived aroma of crumb with crust was influenced more by volatile profiles than by crumb texture. It thus contributes to our understanding of aroma perception dynamics and the mechanisms driving volatile release during oral processing in bread.

An experimental model to investigate the biomechanical determinants of pharyngeal mucosa coating during swallowing

The development of innovative experimental approaches is necessary to gain insights in the complex biomechanics of swallowing. In particular, unraveling the mechanisms of formation of the thin film of bolus coating the pharyngeal mucosa after the ingestion of liquid or semi-liquid food products is an important challenge, with implication in dysphagia treatment and sensory perceptions. The aim here is to propose an original experimental model of swallowing (i) to simulate the peristaltic motions driving the bolus from the oral cavity to the esophagus, (ii) to mimic and vary complex physiological variables of the pharyngeal mucosa (lubrication, deformability and velocity) and (iii) to measure the thickness and the composition of the coatings resulting from bolus flow. Three Newtonian glucose solutions were considered as model food boli, through sets of experiments covering different ranges of each physiological parameter mimicked. The properties of the coatings (thickness and dilution in saliva film) were shown to depend significantly on the physical properties of food products considered (viscosity and density), but also on physiological variables such as lubrication by saliva, velocity of the peristaltic wave, and to a lesser extent, the deformability of the pharyngeal mucosa. The biomechanical peristalsis simulator developed here can contribute to unravel the determinants of bolus adhesion on pharyngeal mucosa, necessary both for the design of alternative food products for people affected by swallowing disorders, and for a better understanding of the dynamic mechanisms of aroma perception.