When making curd, it's good to use bottled juice for consistent acidity, but I prefer fresh limes and lemons! Just make sure to use a variety high in acidity to keep it safe.
(This recipe can be cut in half. You can also use this for orange curd, but the acidity isn't high enough for safe canning, so use right away or freeze any orange curd.)
Lime or Lemon Curd:
zest of 14 limes (or zest of 10 lemons)
2 c. lime or lemon juice (about 14 limes or 10 lemons)
8 whole eggs
14 egg yolks
2 tsp. salt
5 c. sugar
1 1/2 c. unsalted butter, melted
large stock pot with metal rack
9 half-pint canning jars with rings and new lids
double boiler, or a large stock pot & metal bowl
instant read thermometer
1. Thoroughly wash and scrub the limes, then dry with a paper towel. Using a citrus zester (or grater if you don’t have a zester), remove the zest from the limes, avoiding the bitter white pith.
2. Cut the limes in half, and juice. You will need 2 cups of lime juice total.
3. Heat up your double boiler, or you can do what I do and place a large metal bowl over a pot of simmering water. Add the sugar, whole eggs, egg yolks, salt, and lime zest. Mix thoroughly with a whisk.
4. As you continue whisking, add the lime juice. Then add the melted butter. (Wear oven mitts while doing this for safety) Continue cooking the mixture slowly over the simmering water, while whisking. Check with the thermometer regularly. Once the mixture starts to thicken, and it reaches 170 degrees F, turn off the heat and remove the pan to a kitchen towel.
5. Strain the curd into a clean glass or metal bowl. This is to remove any curdled bits, egg chalaza, and the zest. Your curd is now ready to can. (If you prefer to refrigerate, use within a week, or freeze for up to 1 year.)
6. To can the lemon curd, sterilize the jars, rings, tongs, and ladle in boiling water for 10 minutes. Turn off the heat. Remove the hot jars to a kitchen towel, and fill with hot lemon curd, leaving a 1/2″ head space. While filling the jars, soak the new lids in the hot water. Wipe the rims, top with the lids, and screw the rings down finger tight.
7. Make sure the water in the stock pot (with metal rack in bottom) is no hotter than 180 degrees. (Cool down with cold water if needed before proceeding.) Set the filled jars on the rack inside the stock pot. Make sure the water covers the tops of the jars by at least one inch. Turn on the heat, and bring the water back up to a boil (covered). Once boiling, let the jars process for 15 minutes (if below 1000 ft). You will need to add an extra 5 minutes processing time for every additional 5000 ft in elevation.
8. When the processing time is up, carefully remove the hot jars to a kitchen towel. Do not the disturb the jars – you will hear a “pinging” sound as the jars cool – this is part of the sealing process. The next day, test for a proper seal by depressing the lid with a finger, making sure it does not move up and down. Use home canned curd within 3-4 months, separation or color changes may occur with longer storage.