how sulfite is naturally produced in wine?

Question

by the alcoholic fermentation yeast.
everwhere, it says sulfite is added but it is also produced by the wine naturally, but no one gives the names of the yeasts which produce sulfite.
if possible
please give the name of the yeast and reaction, also reference, if you can.
or just help me, this is so urgent...
thanks

Answer 1

The fermentation process is a complicated chemical reaction and I am not enough of a scientist to understand it more than sketchily -- may I suggest the new book by Jamie Goode written for lay people -WIne Science

"When a yeast cell finds its preferred nitogen source (ammonium and amino acids) in limited supply, it can turn to two sulfur-containing amino acids, liberating the sulfur in them as hydrogen sulfide. Winemakers also find that many conditions of no-nutritional stress (e.g. temperature change or dry-goods additions) can also cause yeast to produce hydrogen sulfide"

Phill Spilman winemaker at Villa Maria quoted in WIne Science by Jamie Goode.

But thats not the only ones sulfur comtaining marcaptans (volatile thiols) are produced by yeasts acting on precursors in the must and grape skins -- these are responsoble for manyof the flavors in SauvignonBlanc (again from Goodes book).

Theres an entire chapter on it...........

Answer 2

Sulfites are added because it's not naturally occurring in a fermented beverage. There are compounds that break down into hydrogen sulfide (the smell of rotten eggs) but that escapes with the CO2 in the fermentation process as it's a gas. Hydrogen sulfide is not the same as sulfites.

The sulfites you are reading on the label are added as a means of stopping any further fermentation by killing yeast (both good yeast used for the fermentation, and any possible wild yeasts good or bad). This is in the form of potassium metabisulfite, or sodium metabisulfate.

The process by which yeast ferments (eating sugar and producing alcohol/CO2) does not generate sulfites...that's why they have to be added (if desired), There are wines and beers and other fermented drinks that do not contain sulfites (because they're not added) but you have to look hard. These are uncommon as the alternative (pasteurizing) is tricky and costly to do without ruining the drink's flavor.

Answer 3

I have always believed that the sulfite is added to kill the naturally occuring yeast cells before they introduce the champagne or wine yeast. Its makes for a better wine.