saw this on a message board...wondering the validity. I have never rehydrated dry yeast since my first batch. I haven't seem to have any problems.
"Jamil says you lose 50% cell count by not rehydrating. Mr Malty calcs are based on rehydration when using dry yeast.
person's question...
What's the difference between rehydrating with water and rehydrating with wort (as you pitch dry into it)?"
message boards' answer....
Osmotic pressure. As the yeast begin to absorb water, initially the cell membrane cannot control what flows across the boundary. Everything flows in and out of the cell upsetting the needed balance of nutrients and salts inside the cells. This immediately kills roughly 50% of the cells.
Even with plain water it is still important to rehydrate at the right temperature (95 - 105F). Too cold or hot will also kill the cells.
"Jamil says you lose 50% cell count by not rehydrating. Mr Malty calcs are based on rehydration when using dry yeast.
person's question...
What's the difference between rehydrating with water and rehydrating with wort (as you pitch dry into it)?"
message boards' answer....
Osmotic pressure. As the yeast begin to absorb water, initially the cell membrane cannot control what flows across the boundary. Everything flows in and out of the cell upsetting the needed balance of nutrients and salts inside the cells. This immediately kills roughly 50% of the cells.
Even with plain water it is still important to rehydrate at the right temperature (95 - 105F). Too cold or hot will also kill the cells.