Associations among fatty food sensations and saliva's emulsifying properties

Abstract

Individuals vary in saliva composition, which could in turn influence variability of oral sensations. This study was designed to investigate associations among saliva's ability to emulsify an oil/water mixture, fatty sensations, and diet. Participants (N = 62) gave sensory ratings for a white chocolate substitute with 0, 0.1, and 1% added linoleic acid. Discrimination sorting tasks were performed using the chocolate substitute with/without linoleic acid and with high/low-fat salad dressing. Participants swished and expectorated an oil/water mixture, and the size of the emulsified layer of this spat-out sample was measured. This novel technique was used to estimate the emulsifying ability of saliva, as oral swishing caused the fat to disperse into the water, stabilized by saliva. Estimated macronutrient intake was assessed by 3-day dietary recalls. Results indicate that people who correctly sorted the chocolate substitute with/without linoleic acid had saliva that better emulsified the oil/water mixture and rated the 1% linoleic acid sample as fattier. Those who incorrectly sorted the chocolate samples rated the 1% linoleic acid sample as more bitter. The same pattern for fattiness and bitterness of 1% linoleic acid samples was observed for those who correctly/incorrectly sorted the high/low-fat salad dressings. Regarding dietary data, the only observed relationship was higher dietary protein intake associated with less saliva emulsion stability over time. Overall, the results indicate relationships among how saliva influences dispersions of fat and fatty sensations, but the role of diet should be reexamined with larger and more tightly controlled groups.

Keywords: diet; emulsions; fat sensation; fattiness; oleogustus; saliva.

Fig. 1.

Data collection process.

Fig. 2.

Photo box setup. The vial on the left is the control and shows what the oil/water mixture looked like before swishing. The vial on the right is the “saliva emulsion,” which is the oil/water mixture after swishing orally for 30 s.

Fig. 3.

Procedure for swish and spit oil/water mixture.

Fig. 4.

Demonstration of the layer measurement (left), and examples of mixtures from individuals with high (top) and low (bottom) saliva emulsifying ability.

Fig. 5.

Upper layer proportion of total expectorated saliva/oil/water, analyzed by performance on linoleic acid (LA) candy discrimination tetrad task (2 control candies and two 1.0% linoleic acid candies, participants asked to sort into 2 groups of 2; individuals who failed are in dark gray, passed are in light gray). Overall main effects of time P < 0.0001 (layer gets smaller over time) and of passing/failing LA tetrad test P = 0.078 (pass > fail).

Fig. 6.

Bitterness and fattiness intensity in fatty candies with 0, 0.1%, and 1.0% added linoleic acid. Analyzed by performance on discrimination tetrad tasks. P-values are adjusted for multiple comparisons using Tukey–Kramer. LA tetrad: 2 control candies and two 1.0% linoleic acid candies, participants were asked to sort into 2 groups of 2; individuals who failed are in dark gray, passed are in light gray. High/low-fat salad dressing tetrad: 2 low-fat ranch salad dressing samples and 2 high-fat ranch salad dressing samples, participants were asked to sort into 2 groups of 2; individuals who failed are in dark gray with diagonal lines, passed are in light gray with diagonal lines.