Chemical and microbiological surveys on the effects of dithiocarbamate fungicides on wine‐making

Abstract

AbstractThe hygienic and technical problems which arise in production of wine from grapes treated with zineb have been examined in experiments carried out under conventional conditions and in small‐scale wine‐making processes.Yeast can develop and ferment even in the presence of relatively large amounts of zineb (up to 500 p.p.m.), the fungicide itself causing some increase in the rate of fermentation.Yeast appears to absorb zineb and to utilise it (as well as other forms of sulphur commonly used to treat wines) and to produce hydrogen sulphide and mercaptans, the fermentation balance being substantially unmodified.In practical conditions the treatment with zineb spray does not appear to influence the composition of natural yeast flora of grapes.The amount of residues recovered on treated grapes is very low (less than I p.p.m.). After the grapes have been crushed these residues are found in the must and at the end of fermentation the main part is collected in the lees after decantation of the wine, and they are recovered unmodified.Hydrogen sulphide, carbon disulphide and mercaptans are produced proportionally to the dose of zineb present in the must. The real influence of the traces of this fungicide on the composition and on the flavour of wine appears to be negligible.