Taste, acid astringent

The odor is faintly caramellic, the taste is acid-astringent and mouthfeel (Arctander, 1967). 

Reddish-brown liquid. Almost odorless sour, strongly astringent taste. Acid to litmus. Affected by light, d" 1.548, Miscible with water, alcohol. May crystallize or... 

Guinotannic acid—a tannin existing in cinchona barks, probably in combination with the alkaloids. It is a light yellow substance soluble in w ater, alcohol, and ether its taste is astringent, but not bitter. Dilute HjSOi decomposes it, at a boiling temperature, into glucose and a red substance—quinova red. 

Hydroxybenzoic and hydroxycinnamic acids are characterized by relatively high flavor thresholds (> ppm, mainly bitter taste and astringency) [82]. On the other hand, their decarboxylated derivatives (Fig. 75.5) can impart very strong phenolic/ clove/smoked flavors to beer because of their low threshold values (ppb order). 

The dihydrate Zn(C2H302) 2H2O is a white lustrous powder faint acetic acid odor astringent taste monoclinic crystals density 1.735 g/cm loses water at 100°C decomposes at 237°C readily dissolves in water, 43g/100 mL at 20°C soluble in alcohol. 

Tannins are amorphous substances, which produce colloidal acidic aqueous solutions with astringent taste. With iron salts (FeCls) they form dark blue or greenish black water-soluble compounds. Tannins form insoluble and indigestible compounds with proteins, and this is the basis of their extensive use in the leather industry (tanning process), and for the treatment of diarrhoea, bleeding gums and skin injuries. 

The following chapter (G2) covers the measurement of acid tastants, i.e., chemicals responsible for the acid and sour taste as well as the perception of astringency. unitgu presents methods for potentiometric and colorimetric titration of acid tastants, and unit... 

Obtained in this way osmocyanic acid is anhydrous, and stable in dry air. In moist air it gives a blue colour, probably owing to the formation of osmium cyanide. It readily dissolves in water, giving an acid reaction. It is also soluble in alcohol, but not in ether. It has an astringent, metallic taste. Analysis agrees with the formula given above.6 It unites with bases to form salts known as osmocyanides, which closely resemble the corresponding ferro- and rutheno-eyanides. 

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