That's a great question, Doug! I think this harkens back to the days when active dry yeast required "proofing" in lukewarm water. This was necessary because the yeast was dried at a high temperature that created an outer coating of dead yeast cells that needed to be dissolved before the living yeast cells could be activated. These days active dry yeast and instant yeast are produced in a similar manner, at lower temperatures. The two types of yeast now perform very similarly, so you can generally skip this proofing step and add the yeast directly in with the flour, even with active dry yeast. The exception to this, as mentioned in this article, is when the recipe calls for very cool water (less than 70°F), in which case it still makes sense to activate the ADY in a small portion of lukewarm water. While ADY may be a bit slower to activate when added in with the flour (because the granules are slightly larger), it will catch up and provide the same rising power as compared to instant yeast. 

Because so many bakers have been taught to always use lukewarm liquid in their yeast-raised baked goods, it can be disconcerting for them NOT to use warm liquid. We want bakers to trust us and our recipes, so going with something that is familiar and traditional makes sense. At the same time, we want to help bakers expand their knowledge and learn different ways of doing things, which is why we present a more variable approach to water temperature in this blog post. 

The type of yeast available to home bakers has shifted over the years, so we want to help bakers adjust to this change without scaring them away. If you'd like to read more about yeast, check out this article. 

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