Interactions with Inorganic Salts, Fruit Acids, Purine Alkaloids, Phenolic Compounds and Ethanol

6 Interactions with Inorganic Salts, Fruit Acids, Purine Alkaloids, Phenolic Compounds and Ethanol 

A well-known phenomenon in inorganic salts is the salting-out effect. Adding sodium sulphate, ammonium sulphate or sodium chloride (common salt), for example, in portions to aqueous systems has the effect of driving out some of the volatile compounds into the gaseous phase, or into a solvent which is immiscible with water. Of the salts mentioned above, only common salt has any relevance to food. Additions of 5 to 15% to aqueous systems result in increases of head space concentration of ethyl acetate, isoamyl acetate and menthone up to 25% [10,32], This common salt concentration, however, is way above what is tolerated normally in foodstuffs. In foods with a normal salt content, the salt has virtually no effect on the vapour pressure of volatile compounds [9,10,32], The same is true for calcium chloride [8[, The possibility, that the salt content of the saliva has some effect on the vapour pressure cannot be ruled out however [32], 

Dry common salt binds acetone, ethanol and ethyl acetate (presumably adsorptively) [6], The adsorption is reversible under vacuum. 

The acetone concentration in the headspace above aqueous systems containing citric acid is clearly reduced [8], whereas the vapour pressure of diacetyl above aqueous systems is hardly affected by malic acid. However, if the system contains both acids (for example 0.7% citric acid plus 0.1% malic acid), the odour threshold of limonene is doubled [32], Nothing is known about the type of interactions. It cannot be ruled out that in foods with a high fruit acid content the release of flavour is negatively influenced (although the dilution of the food by saliva can again reverse the effect). 

Ethanol can - like any alcohol - form acetals with aldehydes (Fig. 5.24). The formation of acetal is reversible. With an acid pH value ethanol and aldehyde are released again. In foods containing ethanol with a pH of 7, part of the aldehyde is bound as acetal. 

---