Sulphitic flavours

Grbin et al. 2007). ATHP reduction may lead to EHTP. As ethanol is a precursor, mousy off-flavour occurs after alcoholic fermentation, preferably after lactic acid bacteria activity. It seems that the formation of mousiness may be induced by oxidation but it is not clear if the effect is on the microorganisms or in any chemical reaction stimulated by the redox potential. Other agents claimed to affect its production (high pH, low sulphite, residual sugar content) (Lay 2004 Snowdon et al. 2006 Romano et al. 2007) are also stimulators of microbial activity and so the true mechanisms are not yet clarified, but the non-enzymatic chemical synthesis has been ruled out in D. anomala (Grbin et al. 2007). 

Due to its properties sulphur dioxide has been used for many centuries mainly for the protection of acidic foodstuffs, especially in the wine industry. However its application is restricted owing to flavour problems occurring at concentrations above 5 mg/kg. It is applied as liquefied gas, a solution in water (H2SO3) or the a.m. salts. In the EC list of preservatives which cosmetics may contain inorganic sulphites and hydrogensulphites are mentioned with a maximum concentration of 0-2% expressed as free SO2. But in finished products it is scarcely used, as these normally do not exhibit the low pH which is required for the antimicrobial effectiveness of sulphur dioxide or sulphurous acid. 

The major chemical reactions that take place during food processing, as would be expected, occur between the main food components—the carbohydrates, proteins, fats and vitamins. These components can react with each other and with various food additives such as nitrites, sulphite, aldehydes and alkali to give food products of lower nutritional value to produce desirable and undesirable browning and flavours and very occasionally to produce toxic materials. 

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