Astringency is a specific oral sensation dominated by a dryness and puckering feeling and is one of the main quality factors for red wines, teas as well as some fruit products. Various hypotheses have been proposed to explain the mechanisms of the astringency sensation; however which prevails is still unknown. Here we used a tribological system to determine if the astringency is predominantly a physical perception. Mixtures of whole human saliva and typical astringent compounds such as tannins and red wines were evaluated for their lubrication behavior. Friction coefficient was measured over a wide range of lubrication speed. By comparing friction coefficient with human sensory results of astringency, a positive correlation was found. In particular the highest correlation was observed (R 2 5 0.93) at a sliding speed of 0.075 mm/s. Results from this work demonstrate that astringency of polyphenol-rich products is a sensory perception via a physical stimulus and can be quantified using tribology techniques. PRACTICAL APPLICATIONSThere is an increasing interest in sensory astringency, particularly its signaling process in oral cavity and the quantitative assessment of its intensity. This is due to the fact that astringency is an important quality characteristic which strongly influences consumer's acceptability for many polyphenol-rich foods. This research achieved the first experimental approach to sensory astringency determination on red wines by using a tribological technique. Results from this work positively confirm the hypothesis that astringency is a tactile sensation. The method established in this work provides a useful tool for efficient determination of astringent intensity both as industrial quality control and for the prediction of consumer's sensory perception.

Astringency is one of the predominant factors in the sensory experience of many foods and beverages ranging from wine to nuts. The scientific community is discussing mechanisms that explain this complex phenomenon, since there are no conclusive results which correlate well with sensory astringency. Therefore, the mechanisms and perceptual characteristics of astringency warrant further discussion and investigation. This paper gives a brief introduction of the fundamentals of oral tribology forming a basis of the astringency mechanism. It discusses the current state of the literature on mechanisms underlying astringency describing the existing astringency models. The review discusses the crucial role of saliva and its physiology which contributes significantly in astringency perception in the mouth. It also provides an overview of research concerned with the physiological and psychophysical factors that mediate the perception of this sensation, establishing the ground for future research. Thus, the overall aim of the review is to establish the critical roles of oral friction (thin-film lubrication) in the sensation of astringency and possibly of some other specific sensory features.

Red wines are characterized by their astringency, a very important sensory attribute that affects the perceived quality of wines. Three mechanisms have been proposed to explain astringency, and two theories describe how these mechanisms work in an integrated manner to produce tactile sensations such as drying, roughening, shrinking and puckering. The factors involved include not only tannins and salivary proteins, but also anthocyanins, grape polysaccharides and mannoproteins, as well as other wine matrix components that modulate their interactions. These multifactorial interactions could be responsible for different sensory responses and therefore need to be further studied. This review presents the latest advances in astringency perception and its possible origins, with special attention on the interactions of components, their impact on oral perception and the development of astringency sub-qualities. Future research efforts should concentrate on understanding the mechanisms involved as well as on the limiting factors related to the conformation and stability of the tannin-salivary protein complexes.

No abstract