Kumquat jam is a wonderful way to enjoy an otherwise tart but flavorful little fruit. Make them into a jam and all that tartness comes through as a glorious full-flavored spread, perfect for your morning toast or elaborate treats.
The first time I tried kumquats was right off the tree in California. Even growing up among the citrus groves, I had never seen or heard of kumquats until high school. One afternoon my team was playing on a new field, and there was a giant kumquat tree hanging over the fence right into the dugout.
We were all curious about them but no one knew what they were. I plucked one off, carefully peeled it and got the surprise of my life. SO incredibly tart!
What I didn’t know was kumquats are eaten whole, peel and all. The inside is very tart, but the skin is mild and sweet. Together they’re a treat with a bit of zing, but without the peel, it’s sour enough to make your eyes water.
When making homemade kumquat preserves, that begs the question, is it a jam or a marmalade? Generally, marmalade is a citrus-based spread that includes peel to add subtle tart/bitter notes to balance the sweetness. But what happens if it’s a type of citrus where the peel isn’t bitter, and you can’t reasonably eat the fruit without the peel?
I call it kumquat jam, you can call it kumquat marmalade if you like, but my kids…they call it delicious.
There are a few different ways to prepare kumquats for kumquat jam, but regardless of the method, the peel is always central to the preserve. In my method, I simply slice the kumquats across the equator, which leaves full rounds of the tiny fruits in the finished jam.
I’ve seen other methods that slice the fruits into strips vertically, cutting them into eighths. That leaves you with thin 1” slices of peel throughout the jam almost like confetti, and that gives a look much more like a traditional marmalade.
Since I want to really play up the uniqueness of these tiny fruits, I find the rounds make for a striking presentation. There aren’t any other citrus fruits tiny enough to cut into rounds for jam, so this kumquat jam catches your attention.
Beyond their tartness, another surprising thing about kumquats is the seeds. For such a small fruit they have some impressively large seeds. Those will need to be removed before the slices go into the jam.
As you’re slicing the kumquats, you’ll find a pocket of seeds towards the center. Simply use the tip of your knife to pull them out and set them aside.
Now you’ll notice I said “set the seeds aside” not “toss the seeds in the compost.” The seeds are actually important to this jam, believe it or not!
Citrus fruits contain quite a bit of pectin naturally, and the seeds have some of the largest concentrations. Those large kumquat seeds are the source of pectin for this jam, and they’ll help it thicken up beautifully without any store-bought pectin.
The trick is, while you need the seeds in the jam pot as a thickener, you don’t want them in the finished jam. Wrapping the seeds up in a bit of cheesecloth means you can put them into the boil as a pectin source, but then remove them towards the end for a clean seedless kumquat jam.
I’ve read that you can also place the citrus seeds in water overnight and they’ll cause the water to gel. That gel can then be added to the jam, instead of the seeds in a cheesecloth packet. I haven’t tried that method yet because I always have plenty of cheesecloth on hand from my home cheesemaking.
The thing you do need to keep in mind though is this jam needs to sit for a while before boiling. All the kumquat slices and the packet of citrus seeds go into the pot with a bit of water, and then they need to soak for 3-4 hours before cooking. At least so they say.
I’ve tried making kumquat jam the inpatient way, and just turned it on and started boiling. It does work and it will gel, but the yield is slightly lower since there’s less pectin. It’s harder to make a low sugar kumquat jam that way since in a low sugar jam the yield is already lower.
If you’re pressed for time and want to just get to it, go ahead. Just keep in mind your last jar of jam might not be all the way full, and you should probably use the full amount of sugar.
Sugar Amounts for Kumquat Jam
The amount of sugar in this jam recipe is a matter of preference. Just like any fruit, kumquats can be really tart or only mildly tart, depending on their source.
If you have fruit that is pretty sweet to start with, less sugar might be a good choice. Likewise, if you have very tart fruit (or like very sweet jams) more sugar is always an option.
I’ve seen some kumquat jam recipes that use 2 cups of kumquats and 8 cups of sugar, and in my mind, that’s just way over the top. At that point, you’re making candy, and the fruit is just in there for color.
This recipe has 2 cups of fruit and 1 cup of sugar, or roughly 1/8th the amount of some you’ll find. Still, I find it pretty darn sweet, and only ever so slightly tart, just enough to taste the fruit. I’d make it like this for my mom, who has a pretty good sweet tooth.
For myself, I’d reduce the sugar further to 1/2 cup of sugar for 2 cups of sliced kumquats. That reduces the yield a bit but suits my tastes better.
Either way, the jam gels just fine since the citrus seeds are in there adding extra pectin and helping to bring everything together. Regardless of the amount of sugar you choose, cook the jam to gel stage (220 degrees F) or test it for consistency on a plate kept in the freezer before pouring it into canning jars.
If you’re at a higher altitude, gel stage adjusts a bit.
For every 500 feet above sea level, drop 1 degree from the jam finished temperature. For example, at 1000 feet gel stage is actually 218 degrees instead of 220.
Kumquat jam is a great way to use an otherwise tart fruit. It makes a beautiful presentation and is perfect for your morning toast or an exotic treat.
- 2 cups sliced kumquats (roughly 3/4 lb)
- 3 cups water
- 1 cup sugar (see note)
- Slice the kumquats into thin slices horizontally across their equator, removing any seeds and setting them aside.
- Wrap the seeds in a bit of cheesecloth, tie it up and place them in the jam pot.
- Add in 3 cups of water and the sliced kumquats.
- Allow the fruit and water to sit for 3-4 hours, so that some of the pectin can extract into the water (this step can be skipped for a slightly lower yield).
- Turn on the pot and bring the mixture to a simmer. Cook for 35 to 45 minutes, adding a bit of water if necessary. At this point the jam should be starting to thicken.
- Remove the packet of citrus seeds and add sugar.
- Simmer the jam for another 5-10 minutes until the jam reaches gel stage (220 degrees F) or gels promptly when a bit is placed on a plate that's chilled in the freezer.
- Funnel into prepared canning jars, remove air bubbles and apply 2 part canning lids.
- Either store in the refrigerator for immediate use, or process in a water bath canner for 10 minutes to make the jam shelf stable.
I often choose to use less sugar, adding only 1/2 cup instead of the full 1 cup in this recipe. That makes a tarter jam, and lowers the yield slightly. Adjust to your preference.