I recently made preserved lemons using a recipe from Jerusalem: The Cookbook. Having poked around a variety of recipes online, it's pretty much the same as all the rest: Lots of salt, squeeze out the juice, fill up the container with more fresh juice, add some rosemary and a red pepper. Float a little oil on top. Let sit in a cool, dark place for 30 days.
I opened the lemons last night, and a considerable amount of gas escaped from the lemon juice, which bubbled for about 2-3 minutes before calming down. The cap on the jar wasn't distended, and the mixture wasn't malodorous in any way. My instinct is to say, "This is bad; throw this away", but I haven't canned anything before so I'm not sure what to expect. What little information I can find on google is either contradictory or tongue-in-cheek and suggest it's fermentation.
What's up with my lemons? Are the gas bubbles escaping from the mixture a sure sign of spoilage?
EDIT: After a week, I'm still not not sure which answer to accept, as this, too, contains contradictory information... I suppose time and votes will tell.