Salivary proteins and volatile release: A model study on transglutaminase

Saliva has a role in the appreciation and acceptance of food and beverages. During eating and drinking, all kinds of oral sensations (taste, viscosity, astringency) are modulated by saliva. Also the retro-nasal olfactory perception is significantly affected by the interaction with saliva mostly as a consequence of its proteins content. We previously found that salivary transglutaminase (TG) could be involved in the alteration of the retro-nasal aroma volatilization in obese individuals likely modifying the sensory perception (1). The relationship between TG and volatile release was investigated in vitro in a model system miming differences in TG levels detected in human saliva from obese (O) and normal weight (N) people. A lower inter-individual variability and a significant high mean value of TG was detected in saliva samples from O with respect to N subjects, showing a recurrent alteration of salivary TG correlated to the weight status. TG interaction with three volatiles – ethyl acetate, benzaldehyde and 2-phenylethanol, were analysed in an artificial saliva solution by DH/SPMEGC/ MS. They were chosen because their release significantly (P<0.001 to P<0.05) diminished (49 %, 21 % and 60 %, respectively) when a liquid food matrix (wine) interacted with saliva from O subjects. Results from the model study were analyzed by a two-way ANOVA with interactions an showed that TG can indeed affect volatile release, as well as the quantity and hydrophobicity of the compound, and the interaction between concentration and hydrophobicity of the volatile. Further experiments are needed to determine the exact nature of the impact of TG on aroma release and perception. These results contribute to testing the hypothesis of a lower retro-nasal stimulation in obese people and to the understanding of its origin.