Annamaria Recchia

Saliva Characteristics and Individual Sensitivity to Phenolic Astringent Stimuli

Astringency sensation is due to interactions between salivary proteins and phenols and is based on an increased-friction mechanism. Modifications to the profile of salivary proteins and their concentration could affect tannin/protein reactions and hence the intensity of perceived astringency. Salivary characteristics of 65 subjects were compared after abstention from phenol-containing food and immediately after ingestion of tannic acid. The effect of stimulation on saliva characteristics was expressed in terms of D value, computed as the arithmetic difference between values found in saliva samples from the 2 conditions. Based on D values, subjects were clustered in two groups. Cluster 1 (Cl1, 53 cases) was characterized by low D values thus indicating that the basal saliva condition was quickly restored in these subjects. Cluster 2 (Cl2) was composed of 12 subjects whose basal salivary condition was not quickly restored, particularly in terms of salivary protein concentration and profile and saliva haze-forming capacity. Sensory data showed that subjects capable of maintaining constant saliva characteristics were less sensitive to astringent stimuli than subjects in which the same stimulations induced significant saliva modifications. The results suggest that a large proportion of the population are able to maintain their salivary protein concentration and simultaneously intercept and inactivate dietary tannins.

Individual astringency responsiveness affects the acceptance of phenol-rich foods.

Sensory responses greatly vary between individuals, and individual sensory experiences influence eating behaviour. Three groups responding differently to phenolic astringent stimuli (Low Responding, LR, n=20, Medium Responding, MR, n=37 and High Responding, HR, n=20) were identified from a population of 77 subjects, based on the maintenance vs fluctuation of salivary characteristics after repeated stimulation of the masticatory and taste/somatosensory systems. The effect of LR, MR and HR status on perceived astringency and liking for phenol-containing apple, grape and carrot juices spiked with increasing tannic acid (TA) concentrations was examined. TA induced a greater increase of perceived astringency in HR, compared to MR and LR subjects. A decrease in liking for spiked juices was found in HR and to a lesser extent in MR and LR subjects. No significant differences were found comparing MR and LR groups for both astringency intensity and liking data. Liking for and familiarity with 37 food items, as well as preference for 14 phenol-rich foods and beverages, each paired with a less astringent counter-product, were also examined. An internal preference map was computed on liking scores and product subgroups were identified. An effect of LR/HR status was found for two food subgroups consisting of coffee without sugar, tea without sugar, raw chicory and milk chocolate, tea with sugar, coffee with sugar. LR subjects rated the products with the most astringency higher and those with the least astringency lower than did HR subjects. LR subjects also rated their familiarity with highly astringent products higher than did HR subjects. Thus, individual differences related to the physiological salivatory response to oral stimulations affect responses to astringent stimuli and can influence the overall acceptability of phenol-rich food items.