Did you follow the correct processing time for the recipe and size of jar? If so, you're fine.

Master Canner here (and that's not self dealed! I'm certified by the state of WI to give advice on canning.) Canning is kitchen chemistry at it's finest. It's critical to keep ratios intact for both taste and safety. That being said, jams are the most forgiving of all processed foods.

Looking at the ratios in your recipe, it doesn't look "doubled" to me. That's actually about the average output for a recipe. Maybe you used a "small batch" recipe?

Enjoy your jam and keep making it!

The warning about not doubling jam and jelly recipes is not about food safety--it's about quality and texture and looks. Doubling, even if you measure and time everything exactly twice what ithe recipe calls for, could result in a softer spread and/or dull, drab or caramelized color. It might not happen every time you double, but why spend all that time and money making what you think is strawberry jam but is actually strawberry pancake syrup?

I have a recipe for beet jelly that is such a beautiful garnet it looks like a magazine photo. The recipe was given to me with a specific written and verbal warning against doubling it. I did it anyway. It tasted great and it jelled up nicely, but instead of the jewel-like garnet, the beet jelly looked like beets, kind of earthy and muddy. The only thing my friend Cathy had to say was, "Toldja so."

A couple years ago, my oldest son moved into a house that had a lovely, mature tree in the backyard that produced incredibly sweet golden plums with puckery tart skins. He gave me more than a bushel of dead-ripe fruit on a day that I was short on time, so I doubled the plum jelly recipe--twice. It turned out to be like liquid amber, something that was thicker than syrup, like a pourable jelly. So, two days later when I had the time, I dumped everything into a stock pot, washed and sterilized the jars, measured out four cups of the almost-jelly into a pot, added lemon juice and pectin, recooked it, then processed the jars again. I was able to save it, and the plum jelly was really good, sweet and tart at the same time, like a good plum, and it jelled up nicely, so I guess it was worth the extra work. It would have been more worth it if I had done it right the first time.

So be assured you won't kill anyone, though you might want to kick yourself.

I'd say two things. Follow the recipe exactly when you're canning if you plan to store things on the shelf. If you decide to experiment, then refrigerate the jam when you're finished. That way you don't need to worry as much if the acid levels are adequate to store the jam. By the way, there is an incredible book of jam recipes by Christine Ferber. I've made about five of them so far and they are outstanding.