Role of salivary films in assessing astringent compounds

Astringency is the ‘dry puckering’ sensation attributed to consumption of foods and beverages such as green tea. Previous studies have connected this tactile oral sensation to the aggregation and precipitation of salivary proline-rich proteins (PRPs), yet this mechanism doesn’t occur with all astringent molecules. It also doesn’t consider the impact of astringents directly on lubricating <br/>properties of the salivary film and salivary proteins bound to the epithelial layer (mucosal pellicle).<br/>Studies of oral epithelial cells have been used to confirm which proteins form the mucosal pellicle. Model particles with different surface chemistries and tissue cultured cell lines have been used to determine how this pellicle forms. These models were then used to decipher effects of green tea polyphenols on the development and composition of the mucosal pellicle. Interfacial rheological measurements were also completed on the pendant drop tensiometer to study the impact of these polyphenols on the development of the saliva film at the air/liquid interface where an elastic protein-rich matrix is formed.<br/>The mucosal pellicle is particularly mucin-rich with minimal levels, if any, of PRPs. <br/>Epigallocatechin gallate (EGCG), a polyphenol containing a galloyl ring, interacts with MUC5B to a much lower extent than with PRPs. However, this interaction is enough to alter and enhance the binding of MUC5B and other salivary proteins shown to aggregate with polyphenols in pellicle models. This response was echoed with EGCG washes on epithelial cells, indicating improved MUC5B <br/>retention as a result of EGCG interactions. Epicatechin (EC) had<br/>minimal effects on the salivary pellicle, and shows relatively low levels of interactions with salivary proteins yet is still perceived as astringent.<br/>EGCG was also able to alter the interfacial properties of the salivary film to varying degrees among volunteers dependant on salivary protein profiles and concentration. EC however, which has minimal effects except in volunteers with low salivary protein concentration, showed some positive benefits indicating improved wetting properties perhaps due to some surface activity when bound <br/>with proteins.<br/>Astringency is a multifactorial mechanism, in which protein interactions with polyphenols results in PRP and other salivary protein lead to aggregation, contributing to changes in mucosal pellicle composition and alteration of the interfacial properties of the salivary film. These mechanisms contribute to a dry tactile taste sensation in the mouth.

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

King's College London

Year dc:date.issued

2013

Author dc:creator

• Gibbins, Hannah

Advisors dc:contributor.advisor

• Carpenter, Guy Howard
• Proctor, Gordon Burgess

Language dc:language

eng

Identifier

oai:kclpure.kcl.ac.uk:studenttheses/98c69f4b-757f-48d0-a54f-2474e486bb54

OAI identifier oai:identifier

oai:kclpure.kcl.ac.uk:studenttheses/98c69f4b-757f-48d0-a54f-2474e486bb54