Fresh yeast
The same organism as the dried forms, sold alive and wet — which changes how much you weigh out, how long it keeps, and almost nothing else.
Also called compressed yeast (TRADE); cake yeast (US); baker’s yeast block (UK); fresh yeast vs dried yeast (UK)
Fresh yeast is compressed live yeast with its water still in it, sold as a crumbly block. It is the same species as instant and active dried yeast, and a dough made with it ferments the same way.
THE DIFFERENCE IS WATER, AND THE ARITHMETIC FOLLOWS FROM IT. Fresh yeast is roughly seven-tenths water; the dried forms have had almost all of it removed. So a given weight of fresh yeast contains far fewer cells than the same weight of dried, and the conversions in circulation — roughly two to three times as much fresh as dried by weight — are estimates of that ratio rather than a rule. BakeHQ’s yeast converter states its own assumptions rather than presenting a single number as fact.
IT KEEPS BADLY, WHICH IS THE REAL DIFFERENCE IN USE. A live wet block is perishable: refrigerated it lasts a couple of weeks at most, and it deteriorates from the outside in. Dried yeast in a sealed packet lasts many months. This is why fresh yeast is normal in bakeries, which use it within days, and awkward at home.
WHAT IT DOES NOT DO is produce better bread on its own. Bakers who prefer it usually cite dispersion and a slightly gentler start; controlled comparisons showing a flavour difference at the same fermentation schedule are not something BakeHQ has read, and the claim is worth treating with the same scepticism as any other.
What changes if it is left out
Instant or active dried yeast does the same job. The substitution is a weight conversion rather than a reformulation, and the only real change is that the dried forms keep.
Follows from the water-content account above. The conversion figure is deliberately left to the yeast converter, which states its assumptions.
RecordedFollows from evidence recorded elsewhere on BakeHQ
Storage and deterioration
Refrigerated and wrapped, and used within a couple of weeks. It dries and darkens from the surface inward as it ages, and a block that has gone hard, dark or sour-smelling has lost activity and will underperform rather than fail cleanly.
Derived from what the product is — a live, wet, perishable culture — rather than from a shelf-life study. No safety judgement is offered.
RecordedFollows from evidence recorded elsewhere on BakeHQ
Related
Compared in
One side of the comparison.
What it does
Aeration
The same organism as the dried forms, doing the same thing at the same rate once the quantity is converted for water content.
Commonly confused with
The same organism wet or dry, with a weight conversion between them that is widely quoted as though it were exact.