Abstract
Current saliva testing methods rely on cutting edge yet expensive techniques for the detection and analysis of genetic material, proteins and biomarkers for clinical use. However, these techniques are limited in scope and often cannot be used with complex food materials. We propose an efficient ex-vivo tool for evaluating biologically relevant interactions between food components and human saliva using sedimentation velocity analytical ultracentrifugation (SV-AUC). We evaluated macromolecular content from “unstimulated” (US) and “stimulated” (SS) samples pooled from 5 healthy volunteers. Over 90% of total saliva protein consisted of α-amylase and mucin, and up to 10% was secretory immunoglobulin A (SIgA). It was shown that α-amylase concentration increased upon parafilm stimulation, which lead to a decrease in the viscosity of saliva. Then, we used a simple food system (green tea) to evaluate changes in the salivary protein content caused by green tea polyphenols. It was found that aroma release from green tea is highly influenced by interactions between α-amylase and polyphenol epigallocatechin 3-gallate (EGCG). This interaction was found to increase the viscosity of the salivary bulk, suggested to contribute to astringency, and increased the concentrations of β-ionone, benzaldehyde and isovaleraldehyde (P < 0.01), suggested to play a significant role in the characteristic flavour of green tea.
Highlights
Astringency is a complex phenomenon in which some food or drug compounds cause a puckering feeling of the oral epithelium[1]
Studies have shown that green tea polyphenol extract is composed of epicatechin, epicatechin gallate and epigallocatechin gallate (EGCG)[17]
The present study describes an efficient tool for characterising the macromolecular content in “stimulated” (SS) and “unstimulated” (US) saliva using sedimentation velocity-analytical ultracentrifugation (SV-AUC)
Summary
Results are in agreement with similar studies showing a lower viscosity for SS, and this is thought to be attributed to the higher proportion of α-amylase, and small proline rich proteins (PRPs), which have very low intrinsic viscosities, lowering the relative viscosity of the saliva[8,10]. This has later been confirmed by capillary viscometry (Fig. 2). There is no significant change in the distribution of mucin and SIgA peaks as compared to the controls
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