Calling experienced jam makers! I recently learned how to make jam in a cooking class and was warned against doubling recipes. I seem to have forgotten the warning yesterday when I made Strawberry Rhubarb Jam. The jam tastes and looks great, but I hope it will keep on the shelf. I used 2 1/2 lbs. of Rhubarb, 3 lbs. of Strawberries, 4 cups of sugar and 1/4 cup of bottled lemon juice. This batch filled 7 1/2 pt. jars. I followed all the sterilizing and processing rules. What do you think?
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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!
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.