By Tom Lehman, The Dough Doctor
We are often told not to let yeast come into direct contact with salt or sugar, but few of us understand why.
It has to do with the way yeast feeds – by assimilating nutrients through its cell wall, which is made possible by osmotic pressure. However, if there is an excessive amount of salt and/or sugar in the environment surrounding the yeast, reverse osmosis can occur. In this condition the salt and sugar exert a great affinity for liquids, which can either impair the ability of the yeast to feed or, in some cases, draw the plasma material right through the yeast cell wall. When this happens, fermentation of the yeast is seriously compromised. In addition, the plasma material contains glutathione, which acts like the reducing agent L-cysteine, the active ingredient in PZ-44. It affects the flour proteins to make the dough softer and more extensible. While this may not sound too bad, consider that since the yeast may not function as well as anticipated (and the reducing affect is going to be quite random), there is no way to predict how much softer or extensible the dough will be.
To prevent this inconsistency, always try to keep the yeast separated from the salt and sugar. You can accomplish this by putting the salt, sugar and yeast into the water before adding the flour. If you wish, you can add the salt and sugar to the dough water, and then add the yeast to the flour, or you can add the yeast to the water and add the salt and sugar to the flour. This will go a long way toward ensuring dough performance.