I am planning to brew a pumpkin ale later today (my first one), and in preparation I have gone over all the pumpkin recipes on the Cat's Meow as well as those on BeerTools.com. I have also read every post that I can find in an assortment of brewing forums. Some say to add the pumpkin during the boil, while others say to add it to the mash; the mash seems more logical to me in order to achieve conversion of starches (I presume pumpkin has some), so that's what I'm planning to do. Some also say to use only fresh pumpkins, while others say it is okay to used canned pumpkin -- even in the mash -- and some even say that canned pumpkin pie filling is okay; others caution not to use the canned stuff in the mash because of the mess and possible stuck runoffs/sparges. I have a monster bazooka (10 feet long) and have never had a stuck runoff yet, including when I've used high quantities of oatmeal and even a wheat beer made with regular flour, so I'm willing to take my chances.
My question pertains to preservatives. I'm going to the store in the morning to buy the pumpkin, so I'm not sure whether I can find any cans that don't have preservatives; however, assuming the cans do contain something, is it reasonable to expect that the mashing and subsequent 90 minute boil will remove them or dilute them enough that they won't hurt the yeast? I'm planning to mash about 5 pounds of canned pumpkin in 10 pounds of grist to make a 5 gallon batch. There were some comments somewhere during the course of my research that suggested that preservatives are not a problem, but I'd like to confirm that if possible before buying it. For instance, if anyone were to definitively report that they used canned pumpkin containing preservatives and just couldn't get the yeast to ferment, and there are no contrary experiences by brewers who definitely used preservatives without problems, then I'd feel compelled to switch over to fresh pumpkin. The only reason I'm avoiding fresh is that it just seems to entail a lot of extra work that I'd like to avoid if possible.
Any help will be appreciated. Thanks.
Bill Velek