Thiamine
vitamin B1
A micronutrient that helps a ferment finish and lowers SO2 binding.
Typical dose
Small, per the product sheet; often already present in a complex nutrient.
When to add it
At pitching.
In practice
Yeast need thiamine to use sugar efficiently, and a must short of it, a heavily sulphited or botrytised one where wild organisms consumed it first, ferments sluggishly and makes more of the compounds that later bind SO2. Most complex nutrients include it, so a separate addition is mainly for high-risk musts.
Linked faults are the ones this addition either treats or, used wrongly, causes. The fault page says which, and whether it can be undone.
Others in nutrients and enzymes
Diammonium phosphate
Inorganic nitrogen for the yeast, the direct fix for a starved ferment.
Complex yeast nutrient
Nitrogen plus the amino acids, vitamins and sterols the yeast also needs.
Rehydration nutrient
Primes dry yeast with micronutrients before it is pitched.
Yeast hulls
Detoxify a stuck ferment and give the yeast a surface to work from.
Pectic enzyme
Breaks down pectin to clear haze and free juice and colour.
Glucanase
Breaks down Botrytis glucans and speeds lees ageing and filtration.
Beta-glucosidase
Frees the bound aroma compounds locked up in aromatic white grapes.