Q. Use of Sulphur dioxide and sulphites in microorganisms?

Sulphur dioxide as a preservative in wine preparation has been in use since ancient times. It is also used in other foods, like hits and vegetables, for preventing the microbial growth. Sulphur dioxide is effective in inhibiting bacterial and mould growth when compared to yeasts. It is also used in combination with sodium benzoates in fit preparations. Apart from sulphur dioxide, other sulphites, sodium sulphite, potassium sulphide and sodium metabisulphite etc. are also used as preservatives, as they act more or less similarly in inhibiting microbial growth. The inhibition of microbial growth is through the inhibition of certain enzyme systems and other biochemical reactions and is also pH dependent. The sulphur dioxide forms sulphurous acid (H2S03) when it combines with water and is effective at the lower pH values.