Inter-individual retronasal aroma release variability during cheese consumption: Role of food oral processing

The aim of our study was to explain inter-individual differences on in vivo aroma release during cheese consumption by oral physiological parameters. To reach this objective, 34 subjects were recruited. Their salivary flow, oral volume and velum opening were determined. Six cheddar-based melted cheeses with different fat levels and firmness were flavoured with nonan-2-one (NO) and ethyl propanoate (EP). During their consumption (free protocol), in vivo retro nasal aroma release was followed by Atmospheric Pressure Chemical Ionisation-Mass Spectrometry (APCI-MS). Chewing activity was evaluated by electromyography recordings. Bolus saliva content, mouth-coating, and bolus rheology were also determined. Based on the quantity of aroma released before and after swallowing, subjects can be clustered into three groups: the first one (HRG) is characterized by a large quantity of aroma release whatever the aroma compound; the second one (MRG) showed a large release for EP and a lower one for NO; the third group (LRG) was characterized by a low quantity of aroma release whatever the compound. Whatever the group of subjects, fat and firmness effects differed according to the aroma compound. EP release increased with firmness and fat content, whereas NO release was not affected by firmness and decreased when fat content increased. Physiological parameters which better differentiated the three groups of subjects according to their release behaviour were chewing activity, mouth coating and frequency of velum opening. Subjects from HRG were differentiated from LRG subjects by a higher chewing activity, and more frequent velum opening. Subjects from MRG presented a lower mouth coating explaining their lower release of NO, the more hydrophobic compound. This study shows that the total amount of aroma released in the nasal cavity during food consumption depends not only on the characteristics of the product but also on the oral physiology of the subjects and on their food oral processing.