Abstract:
Volatile odorants stimulate the olfactory epithelium orthonasally (i.e., through the nostrils) and retronasally (i.e., through the oral cavity), yet the olfactory literature focuses orthonasal perception. In a previous study, orthonasal Best-Estimate Thresholds (BETs) for “floral” β-ionone were obtained in glasses using the 3AFC procedure prescribed by the ASTM standard E679 with a stop 3 rule applied subsequent to data collection. Genetic data obtained through buccal swabs and blood samples was also analysed and isolated an effect of single nucleotide polymorphism (SNP) xxx on orthonasal sensitivity to β- ionone. The current thesis collected retronasal BETs for β-ionone to compare with this pre-existing data for three research purposes: (1) to evaluate the accuracy of ASTM E679 with a stop 3 rule enforced during data collection for calculating retronasal threshold estimates, (2) to compare the test re-test reliability and sensitivity of these olfactory pathways for clinical use, and (3) to determine the comparative effect of SNP xxx on orthonasal and retronasal sensitivity for commercial application. Using a novel straw method, β-ionone was presented orally to 50 consumers in a simple (water) and a complex food (apple juice) matrix in accordance with the 3AFC method recommended by ASTM E679 with an enforced stop 3 rule. Group threshold estimates calculated according to ASTM E679 were compared to the conventionally-defined group threshold estimates produced by fitting psychometric functions. According to the results: (1) the ASTMbased and conventionally-defined threshold estimates are comparable for retronasally acquired detection thresholds, supporting the use of ASTM E679 with an enforced stop 3 rule applied in future retronasal research, (2) the retronasal pathway is an equally sensitive, yet more reliable, clinical alternative to the orthonasal pathway, and (3) SNP xxx similarly pre-determines both orthonasal and retronasal sensitivity to β-ionone. The implications of these findings are discussed, which encourage further research and the implementation of the retronasal pathway in clinical and commercial pursuits.