What Exactly is Jam?

Curious about what exactly is jam and how it differs from jelly, conserves, and marmalade? Master preserver Allison Carroll Duffy explains it all for you.

Several open jars of jam on a wood table surrounded by different types of fruit.
: beats

Adapted from Preserving with Pomona’s Pectin by Allison Carroll Duffy

What is jam made of?

For all its varied and sometimes complex flavors, jam is actually a very simple food, containing only four primary components: fruit (or occasionally flowers, herbs, or vegetables), acid, pectin, and sweetener.

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There are actually several different types of jelled products, however, and jam is just one of them, so let’s get technical for a moment!

What’s the difference between jams, jellies, preserves, conserves, and marmalades?

Jams, jellies, preserves, conserves, and marmalades are the five different types of jelled products—and they each have their own, unique characteristics.


Jam is mashed fruit that has been jelled. It can come in various consistencies, from smooth to chunky, depending on the size and type of fruit pieces.

Two pieces of buttered toast, one with strawberry jam, on a white plate with a spoon and jar of jam in the background.
: Keller + Keller


Jelly is the jelled juice of the fruit, so it’s relatively clear and contains no chunks.


Preserves are similar to jams. In a preserve, the fruit remains more whole; small berries or cherries are left as is, and larger fruits, such as apples or peaches, are cut into uniform chunks.

Two jars of peach and rhubarb jam with some peaches in the background and a plate with a piece of bread topped with the jam.
: Sara Remington


Conserves are also a lot like jams, but in addition to the primary fruit, they usually contain other ingredients such as nuts or dried fruit.


Marmalades are typically made with chopped citrus fruits and usually include some of the sliced citrus peel.

A jar of orange marmalade with a spoon resting on top and a few orange wedges beside it.
: baibaz

What is pectin and what does it do?

Pectin is a naturally occurring substance found in varying degrees in fruit. Its sole purpose in a jam recipe is to cause the fruit to jell. Apples and citrus fruits have quite a lot of pectin, concentrated in the peel, while other fruits, such as strawberries, have very little.

Originally, jams and jellies were made without adding extra pectin, relying only on the naturally occurring pectin in fruit for the jell. When pectin became commercially available, people had the option to make jam with added pectin, simplifying the jam-making process.

Five jars of jam, two apricot and three strawberry rhubarb jam, with some wildflowers.
: Quentin Bacon

However, this traditional type of pectin (whether found naturally in the fruit, homemade from apples or citrus, or purchased from the grocery or hardware store) can create a jell only when working in conjunction with a large quantity of sugar and the correct amount of acid. Traditional pectins that you purchase at the store may also contain dextrose (a sugar additive) and sometimes preservatives.

Jams and Preserves FAQs

What’s the difference between canned jams and refrigerator jams?

Canned jams are processed in jars in a hot water bath so that they will be shelf stable at room temperature for a long period of time. They are often made in large batches. Refrigerator jams are usually made in small batches and must be refrigerated and consumed within a few weeks.

How do I safely reduce the amount of sugar in my jam?

You can reduce the amount of sugar in your jam without any safety concerns, however, using less sugar can impact the quality of the jam and its ability to thicken and set up. If you reduce the amount of sugar in your jam, you may need to add a low-sugar pectin.

How do I know when my jams or preserves are ready?

There are a few methods you can use for testing if a jam is ready. The quickest is to scrape a wooden spoon across the bottom of your pot. If a line of separation stays visible for a few seconds, your jam is likely ready.

For a more specific test, you can measure the temperature on an instant-read thermometer. Jam typically sets at 220°F (104°C).

Lastly, a popular method for testing is to put a few small white plates in the freezer while you’re making your jam. When you think it is set, put a small spoonful on one of the plates. Let it sit for 30 seconds then nudge the jam. If it wrinkles up, it’s ready. If not, continue cooking for a few more minutes and test again with another plate.

How do I thicken jam without store-bought pectin?

Use or add fruits that are naturally high in pectin. Lemons, limes, and apples are naturally high in pectin. One popular method is to place lemon seeds in a cheesecloth pouch and cook it with the jam until it sets.

Originally published July 10, 2022



  1. Anyone who wants to try making preserves should truly get a copy of Christine Ferber’s “Mes Confitures” (French title, English text). Mme. Ferber is from the Alsace region of France and is world famous for her unique and flavor-packed method which doesn’t use any pectin not found naturally in the fruit.

    Her method involves a lot of macerating time and can take up to 3 days. But about 95% of that is sitting in a fridge and it yields rich flavors with less cooking to dull the flavors and colors. What’s more, her recipes span what’s available throughout the year and are grouped by seasons of fruits’ availability.

    Some of her recipes are more conserve than simple preserves. Conserves, BTW, not commonly found in the US, are complex and can be truly wonderful! Some of Mme. Ferber’s recipes include interesting ingredients like Earl Grey tea and chocolate. Many include European fruit varieties that won’t be found here in the US but local varieties can always be subbed even if the results may be different (would we actually know if they were?).

    Mme. Ferber doesn’t water bath her preserves. I do because I’m American and anxious about sanitation and how things will keep. I just use a Ball or USDA guideline for that.

    Mostly, her approach is unique and should be tried and appreciated. I’ve never made anything we haven’t really enjoyed. And no one will find anything in a supermarket to compare!

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