Capacity of oral emulsification determines the threshold of greasiness sensation

Oil/fat is an essential source of food palatability, and its oral perception plays a key role in influencing consumers' sensory pleasure and preference for a food product. Despite its importance, how oil/fat is perceived inside the oral cavity remains debatable. In this work, the authors hypothesize that the oil holding capacity of saliva determines the sensation threshold of greasiness. That is the occurrence of the greasy sensation is probably when the amount of oil/fat in a food system exceeds one's capacity of oral emulsification. Two experiments were designed to obtain supporting evidence. Specifically, the oil holding capacity of saliva was assessed for individuals based on the amount of β-carotene release, and participants' thresholds of greasiness sensation were also determined. A positive correlation was therefore established between the threshold of greasiness sensation and the oil holding capacity of saliva (Experiment 1, n = 24) (p < 0.05). The hypothesis was further confirmed by the observation of an increased threshold of greasiness sensation when oral emulsification capacity is increased by adding a controlled amount of emulsifier to the food compared to the control group (Experiment 2, n = 6). Our results demonstrate the critical importance of human saliva in influencing one's sensory perception and eating experience of oil/fat.