Substitute for calcium oxide (lime) to keep pumpkin from falling apart The recipe for this pumpkin dessert from Mexico says I should leave the pumpkin pieces submerged in water with calcium oxide (lime) for 3 hours, so that the pumpkin doesn't just become puree when I boil it in a later step.

I read on the internet that lime sold for construction work can contain harmful adhesives and, since I'm not currently in Mexico, I don't know where to buy lime that is safe for the kitchen.

Is there another method to keep the pumpkin from turning into goop?
Your problem is that you're looking for the wrong kind of lime.

Calcium oxide, or Quicklime, is indeed only used for building and chemical purposes.  You want Calcium Hydroxide, otherwise known as Pickling Lime.  You can but it online, or from any store that sells pickling supplies.

And it's a good thing you didn't try the calcium oxide, there's a good chance you'd have blown up the stew.  It heats up when hydrated.