Salivary Proteins Inhibit the Mouth- Feeling of Astringency

Astringency, a dry, puckering feeling of the oral mucosa, occurs after consumption of food and beverages, such as teas and wine, containing tannins and polyphenols. Astringency is assumed to be caused by the binding of tannins to salivary proteins, since proline-rich-proteins and histatins readily interact and precipitate tannins. However, it is not yet fully understood whether it is the binding of the salivary proteins to the tannins that contribute to or inhibit this feeling of astringency.

Objective: To identify the role of saliva in astringency.

Method: Whole mouth saliva was collected from 15 normal healthy subjects, under different conditions: resting, following rinsing the mouth with water (1 min) and after chewing on paraffin film (1 min). At each stage, after the collection of saliva, the same sample of black tea (1 % w/v) was tasted and the relative astringency of the solution rated. The salivary protein concentration was assessed by absorbance 215 nm assay and proteins analysed by SDS-PAGE electrophoresis.

Results: Protein concentrations indicated rinsing with water depleted the mouth of salivary proteins compared to the initial resting level, while chewing restored the concentration of salivary proteins to above resting levels, although no change in oral mucosal wetness was detected. Majority of subjects (10 out of 15) perceived an increase in astringency after washing the mouth with water compared to the astringency rating of black tea at rest. Most subjects then perceived a decrease in astringency following chewing compared to the previous state. A separate experiment revealed several of the proteins interacting following the water washout were salivary in origin.

Conclusion: Results show that salivary proteins in solution inhibit the feeling of astringency, which is partly mediated by salivary proteins adhered to buccal mucosal cells.