A Jam Primer: Peach, Cherry, and Blueberry

The difference between “jam” and “jelly” (not to be confused with “jilly”) is mainly in the preparation: when you make jam, you leave some of the fruit whole; when you make jelly, you start with fruit juice. Jelly is useful in cases of extreme frugality (if, for example, you want to make jelly from fruit skins rather than fruit itself), but otherwise I don’t really see the point. It’s more work and less flavor. So, in our house, we eat jam. Now, if you don’t  cook your jam long enough, or don’t add pectin, you might end up with big pieces of fruit in syrup in the final product, in which case you end up with preserves…and if you’re working with more than one kind of fruit, you’ve got yourself either a “compote” or a “conserve.” All of these are delicious. Today, though, we’re going to concentrate on long-cooked, single-fruit products, aka, JAM.

Let’s talk a little bit about set. If you want a quick-cooking firm set, your best option is to use pectin. I’m not a huge fan of pectin, mainly because I like the concept of a jam made solely from fruit and sugar. Also, if I happen to mess up my jam, I would prefer that it be too loose rather than too hard. Ergo, I don’t use pectin. This means that my jam-making is somewhat unpredictable, depending on the weather, the ripeness of the fruit, and my patience in the kitchen. I didn’t cook the strawberry jam quite long enough, and it turned out more like a sauce (albeit a delicious one). Then I overcorrected with the gooseberries and ended up with something a bit more gluey (again, quite tasty, but difficult to spread). Cookbooks will tell you to cook your jam to 228°F, but I am convinced this is too long. All of these jams were cooked to somewhere between 215° and 218°F. The set is just about right—maybe a tad on the firm side, but more or less like what you would find in a store-bought jam. The real key is to get it above boiling. As soon as the thermometer moves above 212°, you’ll see a change in texture. If you like a soft set, you can stop right there. Don’t double the recipe, as you’ll never get there.

Before you dive in, check out this refresher on canning equipment from Food in Jars, one of my favorite blogs. She’s got lots of great advice on jams and all sort of preserves, so poke around her site if you’re feeling confused. And, as always, the National Center for Home Food Preservation has good advice. The instructions below are for the actual cooking part. When the jam is done, transfer them to hot, sterilized Mason jars, top with hot rubber-ringed lids, and process in a boiling water bath for 5 or 10 minutes, depending on whether you’re working with half-pint or pint jars. They’ll keep for at least a year or two without losing much flavor.

Cherry Jam

3 pounds sweet cherries
2 1/2 c. sugar
2 T lemon juice

Pit the berries and crush them (I like to use a potato masher). Put then in a big pot with the sugar and the lemon juice and bring rapidly to a boil. Cook until it reaches the gelling point (around 30 minutes, could be more depending on the fruit), then transfer to sterilized jars. Process. Makes 3 or 4 half-pints depending on how long you cook it.

Cherry and Blueberry Jam

2 pounds sweet cherries
2 c. blueberries
3 c. sugar

Pit the cherries and combine with the blueberries. Crush and transfer to a big pot. Add the sugar and bring rapidly to a boil. Cook until it reaches the gelling point (around 30 minutes). Transfer to clean jars and process. Makes 3 or 4 half-pints depending on how long you cook it.

Blueberry Lime Jam

The lime is subtle. It both adds a little bit of pectin and somehow brings out the flavor of the blueberries without adding an overt citrus flavor.

5 c. blueberries
5 c. sugar
1/3 c. lime juice
zest from one lime

Crush the berries. Combine all ingredients in a large pot and bring rapidly to a boil. Because the sugar content it higher, this one will come to the gel point more quickly, somewhere in the vicinity of 20 minutes. This means you’ll get more jam: 4 or 5 half-pints. Process.

Peach Jam

6 c. peaches
4 c. sugar
2 T. lemon juice

Peel the peaches by dipping them briefly in boiling water (the skins should slide right off). Crush the peaches and combine the ingredients in a large pot. Bring rapidly to a boil and cook until you reach the gelling point: somewhere around 30 minutes. Makes 3 or 4 half-pints.

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10 comments to A Jam Primer: Peach, Cherry, and Blueberry

  • Awesome. 🙂

    I don’t suppose you have a good hot pepper jam/jelly recipe laying around somewhere do you?

  • localkitchen

    My, you had quite the busy weekend!! It all looks quite delectable.

    228 degrees F for jam seems really high; I usually read 220 degrees, or 8 degrees above the temp of boiling water (depending on your altitude). I even think 220 degrees is too high; like you I usually get to about 215 or so and call it a day.

    I’ve overcooked many a jam, trying to get to the elusive 220 degrees; some of them end up like hard candy! I’ve found that a teaspoon or so of water, added to the top, and then 30 seconds in the microwave, loosens the jam up nicely so that you can spread it on toast.

    This year I seem to be going in the opposite direction and many of mine are ending up quite soft, but, I agree again; too soft is better. You can always spoon it over ice cream, but a jar full of hard crack candy is a little less useful. 🙂

  • Those jams look absolutely delicious!

  • dorisandjilly

    Lindsay: for hot pepper jelly you definitely need pectin–in fact, you’ll need liquid pectin. I’ve made it once before but lost the recipe…the online sources vary wildly from 1/2 c to 2 c. of peppers, from 4 to 6 c. of sugar, from 1 to 2 1/2 c. cider vinegar, and either 1 or 2 pouches of pectin. Kraft (manufacturer of pectin) has several on its Web site. So, I can’t offer advice, but would love to hear what you find out!

  • I had my first taste of hot pepper jelly recently and I’ve been on a mission to figure out the recipe since. Thanks for the advice! I’ll definitely let you know if I find a good one. 🙂

  • David R

    An old post, but for reference: Harold McGee says “The boliling is continued until the temperature of the mix reaches 217-221 deg F, which indicates that the sugar concentration has reached 65%.”

  • Molly

    Hello there –

    Just returned from a weekend in Connecticut and have lots of wild blueberries; will I be able to safely use wild blueberries in lieu of the regular blueberries in your blueberry-lime jam recipe? (I’m not sure if the acid content in the berries is different…)


  • dorisandjilly

    @Molly Wild blueberries should be fine. You may need to add more or less sugar, depending on your sweetness preference, but it’s not a safety issue. Happy canning!

  • Sheila


    Curious what your opinion is of doubling recipes when you aren’t using pectin? For example, could I double the blueberry lime recipe you have above? Also, could I reduce the sugar in this if I want more of a kick OR should I add more lime?

    We prefer less sugar. I’ve made a cranberry apple jam with much less sugar than it called for and we loved it. Then made the same recipe with ALL the sugar it called for with a friend and hers was good too…though much too sweet for most of us!

    Thank you, again, for your hard work for all of us fellow canners and cooks!

  • dorisandjilly

    Sheila: I would not recommend that you double the recipe. Pectin or not, in either case you’re trying to boil down the jam to the right consistency. If you double it, it will take much longer, and you’ll end up with more of a cooked fruit stew than a jam. Happy canning!