RELATION BETWEEN SENSORY ASTRINGENCY OF EXTRACTS FROM SELECTED TANNIN-RICH FOODS AND THEIR ANTIOXIDANT ACTIVITY

ABSTRACT

Extracts obtained from hazelnuts, walnuts, almonds, vetch seeds, buckwheat and buckwheat grits were examined for their sensory astringency and antioxidant properties. The sensory astringency was evaluated using the sensory scaling method and was expressed as sensation of astringency index (SAI). The antioxidant activity of extracts was analyzed using (1) total antioxidant activity (TAA), (2) the ability to scavenge the 2,2-diphenyl-1-picrylhydrazyl radical, (3) bleaching of β-carotene and (4) reducing power. Human salivary protein (HSP) precipitation capacity of the extracts was assayed by spectrophotometric techniques. Statistically significant correlations (P ≤ 0.05) existed between SAI values and TAA, SAI value and reducing power, and SAI values and HSP precipitation. The presence of condensed tannins in the extracts was confirmed by UV spectral and high-performance liquid chromatography data.

PRACTICAL APPLICATIONS

The sensory astringency of the tannin-rich extracts is correlated with their antioxidant activity. This information and the regression equations reported in this study could help to prepare functional foods characterized by the high antioxidant properties that could meet consumer's acceptance. However, studies should continue to explain whether the masking of astringency of plant extract with hydrocolloids may render any undesirable effect on their antioxidant properties.