Vi har hatt en diskusjon gående på Norbrygg etter at noen mente at gjær som har gått et fullt forløp ville være bedre rustet for gjenbruk, noe jeg slett ikke var enig i. En av deltakerne sendte likegodt mail til de tre mest kjente produsentene – og dette er svarene han fikk:
”Hi Tore- So you are correct that traditionally yeast harvesting was done by top cropping. It is a superior method in professional brewing because when the yeast flocculates to the bottom of the fermentor there is a lot of pressure from the liquid above on the yeast and it's very healthy at that point. Although it is better it's a very unlikely practice in the US. I would not worry about this in a homebrewing setting but this often becomes an issue in brewers when they start growing and get into 30+HL size fermentors. Additionally, making a larger starter and storing it for later is totally fine practice as long as it's clean! Hope that helps.”
TECHNICAL LABORATORY MANAGER, White Labs
”I'd say the healthiest yeast will be the extra yeast you harvest from the starter as it is produced in the best environment (lower gravity wort, lower constant CO2 levels, likely higher O2 during growth, no hops, etc.
The top cropped yeast would be second best due to lower exposure time to the fermentation byproducts (alcohol and CO2).
The yeast cake will likely be the least happy due to the opposite... longer exposure times to alcohol and CO2.
I would also add that it's important to refrigerate the harvested yeast from any of these process as quickly as possible to preserve the health of the yeast... i.e. avoid warm storage once nutrients are depleted.”
TECH LEAD, Imperial Yeast
Wyeast ga ikke noe ordentlig svar, dessverre. Takk til Tore hos MonoBryggeriet for utmerket research. Både White Labs og Imperial Yeast anbefaler altså å høste overskudd fra startere, så lenge man er nøye med hygienen.