Retronasal aroma dynamics related to the swallowing threshold

The state of food comminution caused by chewing is an important factor triggering the swallowing reflex. However, the impact of retronasal aroma released from comminuted food to the nose upon swallowing during food intake is poorly understood.

The present study investigated the relationship between aroma concentration and swallowing threshold while chewing a standardised test food.

Twenty healthy participants took part in this study. Concentration of retronasal aroma was measured over time through the nostrils using an odour sensor. The aroma concentration was measured while chewing an orange-flavoured gummy jelly until swallowing, and the number of chewing strokes was measured to determine the swallowing threshold. Next, the aroma concentration was measured while chewing the gummy jelly for 30 strokes, and 100% and 200% of swallowing threshold without swallowing. The surface area increase in the expectorated gummy jelly pieces was calculated using image analysis and defined as masticatory performance at 30 strokes.

The average number of chewing strokes until the swallowing threshold was 45.1 ± 14.2. Higher masticatory performance was associated with a smaller number of chewing strokes at swallowing threshold, and a greater increase in surface area at the swallowing threshold. The number of chewing strokes and the aroma concentration were similar between the swallowing threshold and at the maximum aroma concentration while chewing at 200% of the swallowing threshold.

The findings suggested that the swallowing threshold might be influenced by retronasal aroma concentration as well as the state of food comminution.