Brewpastor
Beer, not rocket chemistry
Jamil spoke recently on one of his shows of an abstract from a comparision of dry and liquid yeast. Jamil was stressing the use of liguid yeast over dry. I know there has been great debate on this issue and was interested to read the abstract. So I sent him a note and got the following response, which I pass along for your information.
Tom,
It was an ASBC paper. Here is the abstract:
ABSTRACT
J. Am. Soc. Brew. Chem. 60(3):135-139, 2002
Strains of freshly propagated ale and lager yeast were compared with identical dried strains during wort fermentations. While several factors remained within standard expectations and were favorably matched to freshly propagated yeast fermentation results, a number of undesirable characteristics were associated with the dried yeast brews, especially reduced viability. The Helm flocculation test and static fermentations showed that flocculation is affected by the drying process, especially with lager strains. Also, dried yeast seems to induce a greater amount of haze in suspension, and the fermentation has a considerably less stable foam than fermentations with the fresh yeast samples, which may be due to the increased levels of extracellular proteinase found. It is suggested that many of the effects observed are a result of pitching high levels of dead yeast into the wort and that this could be alleviated by increasing the viability of the dried yeast, possibly by propagating on carbon sources such as maltose to increase levels of trehalose, a reported stress protectant
brew strong,
JZ
Tom,
It was an ASBC paper. Here is the abstract:
ABSTRACT
J. Am. Soc. Brew. Chem. 60(3):135-139, 2002
Strains of freshly propagated ale and lager yeast were compared with identical dried strains during wort fermentations. While several factors remained within standard expectations and were favorably matched to freshly propagated yeast fermentation results, a number of undesirable characteristics were associated with the dried yeast brews, especially reduced viability. The Helm flocculation test and static fermentations showed that flocculation is affected by the drying process, especially with lager strains. Also, dried yeast seems to induce a greater amount of haze in suspension, and the fermentation has a considerably less stable foam than fermentations with the fresh yeast samples, which may be due to the increased levels of extracellular proteinase found. It is suggested that many of the effects observed are a result of pitching high levels of dead yeast into the wort and that this could be alleviated by increasing the viability of the dried yeast, possibly by propagating on carbon sources such as maltose to increase levels of trehalose, a reported stress protectant
brew strong,
JZ