The Polish culture is one of Sourdough International's collections of more than 16 authentic sourdough cultures from around the world. It is our newest acquisition from a tiny Polish bakery. It produces a fantastic dark pumpernickel rye that you won't believe until you bake it. Refrigerated sourdough cultures become dormant but stay viable for many months requiring feeding only to reactivate them before use. The included instructions describe in detail how to activate, reactivate and use our cultures. Ed Wood's most recent book "Classic Sourdoughs, Revised" contains detailed information for using, maintaining and being successful with sourdough cultures. It also contains a wide range of recipes for our sourdough cultures [except the most recent Polish]. None of our cultures ever use commercial yeast in any form. All of our cultures can be used with any of the available home bread machines if used as Ed does for mixing and kneading only. Most bread machines are unsuitable for baking authentic sourdoughs since they do not have "bake only" cycles and thus do not permit the long fermentation cycles required to produce the sourdough flavor.