Analytical ultracentrifugation in saliva research: Impact of green tea astringency and its significance on the in-vivo aroma release

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.

Mucin immobilization in calcium alginate: A possible mucus mimetic tool for evaluating mucoadhesion and retention of flavour

“…Previous ex-vivo experiments using real human saliva have also confirmed a significant reduction in the headspace concentration of linear aldehydes, but not to this extent [28]. It is worth highlighting potential issues associated with the validity of this and other similar ex-vivo tissues [29].…”

Submaxillary Mucin: its Effect on Aroma Release from Acidic Drinks and New Insight into the Effect of Aroma Compounds on its Macromolecular Integrity

“…During consumption of food, saliva is the first medium encountered by aroma compounds as they travel to the respiratory tract and to the olfactory receptors in the nose [3]. Saliva consists of a number of macromolecular components which protect and lubricate the lining of the oral cavity: mucins, amylases, proteins and antibodies, which play a role in regulating pH and normal functioning of the salivary film [[4, 5]. Mucin glycoproteins are the second most abundant salivary components, after salivary α-amylase, and define the structure and functionality of saliva [6].…”

“…These salivary changes trigger salivary glands to produce more saliva in order to compensate for the loss in functionality and to keep the oral cavity lubricated [8]. But the process is faster at replacing low molecular weight enzymes and peptides, and rather slow at replenishing viscous, higher molecular weight mucins, therefore stimulated saliva has lower mucin levels than resting saliva [5]. This effect is predicted to influence the partitioning of aroma compounds from the saliva to the olfactory receptors.…”

Masking the Perceived Astringency of Proanthocyanidins in Beverages Using Oxidized Starch Hydrogel Microencapsulation

“…Many mechanisms of astringency have been proposed, including the loss of lubrication, the inactivation of neuroepithelial taste receptor cells (TRCs), and the interaction of polyphenols with salivary proteins [ 8 ]. Among them, the most established mechanism involves the interaction of astringency-causing polyphenols and certain salivary proteins, such as proline-rich proteins and α-amylase [ 9 ]. This interaction induces the aggregation and precipitation of the salivary proteins, eliciting the sensation of dryness and the astringency feeling.…”