Novel Methods to Evaluate Functional Saliva Characteristics Related to Food Perception

OBJECTIVES: Saliva is the first digestive fluid that food encounters, and likely influences oral sensations and gastrointestinal processing of food. Yet, the pandemic drastically altered risks associated with saliva analysis. Thus, we developed novel functional assays to assess saliva remotely. We aimed for assays that could be self-administered by participants and that would reflect functional characteristics (emulsion stability, starch digestion) of saliva. METHODS: Two assays were developed: stability of oil/water emulsions created with saliva, and digestion of starch by salivary amylase. In the saliva emulsion assay, 7.5 mL of water with 1% purple food color and 7.5 mL of vegetable oil were provided to participants. Participants swished the oil/water mixture for 30 s and expectorated. The expectorates were analyzed for emulsion stability (size of “cream” layer). This stability was compared with dietary intake of fat and sensory ratings of fatty acids. In the salivary amylase assay, saliva was collected by chewing wax for 30 s. Saliva was then mixed with a starch-thickened commercial pudding. The flow of pudding/saliva mixture through a 10 mL syringe was measured from 2–8 min after mixing. The flow rates are being compared to dietary intake of starch and sensory perception of starchy foods. RESULTS: In the saliva emulsion assay, greater emulsion stability corresponded to more intense sensation for fatty acids, indicating smaller, more stable droplets cause greater fat taste sensation. In the salivary amylase pudding assay, analysis indicates wide variability in rate of starch digestion. Some participants’ saliva/pudding mixtures emptied almost completely from the syringe at 2 min, while others had almost no flow through the syringe after 8 min of digestion. Analyses of how the digestion rates compare to dietary starch and sensory perception is ongoing. CONCLUSIONS: These relatively simple assays for saliva function could be useful in future studies aiming to understand how oral digestion influences sensory properties of food, such as thickness or fattiness. Additionally, relating dietary habits to these salivary characteristics may help understand how behavior could influence these functional aspects of saliva. FUNDING SOURCES: NIDCD R21DC017559, USDA Hatch Project 1,013,624.