The Influence of Acid on Astringency of Alum and Phenolic Compounds

Abstract

Astringency of aqueous solutions of phenolic compounds (grape seed tannins, tannic acid, catechin and gallic acid) increased upon addition of citric acid, whereas the astringency of alum was reduced. Astringency of alum was decreased equivalently by addition of equi-sour levels of lactic acid, citric acid or hydrochloric acid. The difference between alum and the phenolic compounds is speculated to result from chemical modifications affecting binding of the astringents with oral proteins rather than cognitive differences. Chelation of the aluminum ion in alum by acids reduces its availability for interacting with salivary proteins or epithelial proteins. In contrast, the increased astringency produced upon acidification of phenolic compounds is speculated to result from the pH driven increase in the affinity of the phenols for binding with proteins. These results suggest that alum cannot be used interchangeably with phenolic astringents in psychophysical studies.

Effect of copper speciation at different pH on temporal sensory attributes of copper

“…Again it should be emphasized that this is only valid in the range of the copper concentration close to the level used in this study. Effect of pH on astringency has been reported in several studies (Lawless, Corrigan, & Lee, 1994;Lawless, Horne, & Giasi, 1996;Peleg et al, 1998;Sowalsky & Noble, 1998). Astringency of acids was a function of proton concentration, and it might be because low pH causes conformational changes of oral proteins (Lawless et al 1996;Sowalsky & Noble, 1998).…”

“…Metallic aroma is assumed to result from oxidation of lipids in the epithelial tissues (Glindemann, Dietrich, Staerk, & Kuschk, 2006). Trigeminal response includes astringency (Keast, 2003;Lim & Lawless, 2005a;Zacarias et al, 2001) that is a tactile sensation caused by de-lubrication of the oral cavity due to precipitation of salivary proteins or cross-linking of epithelial proteins (Breslin, Gilmore, Beauchamp, & Green, 1993;Kallithraka, Bakker, & Clifford, 1997a, 1997bPeleg, Bodine, & Noble, 1998;Sarni-Manchado, Cheynier, & Moutounet, 1999). It was observed that astringency associated with metals was also related to precipitation of salivary proteins .…”

Present and Future Role of Chitin and Chitosan in Food

“…Hydrophobic, electrostatic interactions and/or hydrogen bonding may be the mechanisms involved in protein-chitosan interaction similarly to protein-tannin. [87][88][89] Astringency may be the result of a rise in amine protonated groups when chitosan is dissolved in acidic medium, which would augment the salivary protein binding affinity.…”

Características físico-químicas e sensoriais de aves e ovos

“…Os fenólicos, em plantas, são essenciais no crescimento e reprodução dos vegetais, além de atuarem como agente antipatogênico e contribuírem na pigmentação. Em alimentos, são responsáveis pela cor, adstringência, aroma (Peleg et al, 1998) e estabilidade oxidativa (Naczk & Shahidi, 2004, Angelo & Jorge, 2007.…”