Blueberry jam

Learn how to make homemade blueberry jam with this easy recipe. You'll soon realize that to make the best blueberry jam, you only need three ingredients and no pectin, as long as you boil it to the jam setting point!

Ingredients to make the best blueberry jam

To make any jam at home, including blueberry jam, a lot of people are surprised that you don't need any special ingredients. The proof is this homemade blueberry jam only requires three ingredients to make:

• Fresh blueberries, ideally a mixture of wild and farmed blueberries in season
• Granulated sugar, but you can also go wild and try some alternative sugars, like brown sugar, or a combination of granulated sugar and honey or maple syrup.
• Lemon juice, which helps ensure the perfect set, balances out the sugar, and also makes sure the pH of preserves is safe for canning.

Ratio of fruit to sugar

You'll notice that we aren't using pectin in this recipe. Blueberries are quite high in pectin, especially when compared to other fruit used in jams, like rhubarb, which is very low in pectin.

The key to making preserves and jams that set properly without pectin is using the right ratio of fruit to sugar, and to boil the jam for long enough to evaporate the water. That evaporation concentrates the mixture, making it thicker, less fluid and thin.

For blueberry jam, I like to use a ratio of 2 parts fruit to 1 part sugar, by weight, so for 1 kilogram of prepared fruit, I use 500 grams of sugar. If you prefer to talk in percentages, 33 % of the total weight of ingredients is sugar and 67 % is fruit. There's also a quarter cup of lemon juice, and though lemon juice is an essential ingredient in homemade jams, the weight is pretty insignificant compared to the weight of sugar and fruit.

Key steps and techniques

Like with most jam recipes, the basic steps are all the same and you can use the same techniques to make blueberry jam at home:

• Prepare the fruit. You may have to wash or clean the fruit, sorting through it to remove any stems or leaves, but also to remove any fruit that isn't looking good. Berries that are past their prime won't make better jam, contrary to popular belief.
• Macerate the fruit with the sugar and lemon juice. Macerating helps the sugar dissolve, bringing some of the juices out of the fruit. Combined with heat, this step ensures that the pectin is released into the mixture, which will help ensure the perfect set.
• Boil the fruit until the jam setting point. You'll notice in the blueberry jam recipe below, this is done in two stages
  1. heat the mixture until the sugar dissolves, then remove a portion to blend it
  2. boil the mixture until it reaches the jam setting point, around 102–103 ºC (or 215–217 ºF).
• Seal the jars of blueberry jam, either by boiling the closed jars in boiling water for a full 10 minutes or by inverting the closed jars upside down for 3 minutes. For more information on canning, read this guide to home canning.

Ensuring the perfect set with the jam setting point

Have you ever made jam that is thin and runny, and seemingly lacking in flavour? It's likely you didn't boil the jam long enough to hit the jam setting point, the temperature where the jam has boiled for long enough that a good portion of the water has evaporated and the pectin can do its job of setting the jam texture so it's thick and not so fluid and liquid.

Remember fruit contains a lot of water. Blueberries are made up of over 80 % water, and once you heat the berries, the fruit burst and the water is released into the jam, making a very soupy preserve if you don't boil it for long enough.

With most jam recipes, it's hard to give a cooking time because some jams can take even an hour of boiling to achieve the perfect set. I boiled this batch of blueberry jam for 30 minutes, until it reached 103 ºC (217 ºF). I think I could have actually pushed it further and boiled it for longer, but I liked the taste and texture at this point so I proceeded to can it.

You could also boil a little less, to 102 ºC (215 ºF) but make sure that you let it boil to that temperature and make sure it stays there for long enough. Recall, this is the same for marmalade, which also has to be boiled to a certain temperature to achieve the marmalade setting point.

Special equipment for making jam at home

I highly recommend investing in a canning kit made up of the smaller tools you will need in order to properly seal your jars, including a magnet to transfer the clean lids to the jars to avoid contamination, as well as a headspace measuring tool to make it easier to verify that you are filling the jars correctly, and a non-reactive funnel that will help you fill the jars without spilling and without dirtying the edges (which would ruin the seal!).

The kit should also come with jar lifters which are so helpful when moving the jars in and out of the water bath! You will also need a big pot preferably with a rack, like this one on Amazon, in order to boil the jars of marmalade for 10 minutes.

In order to achieve the perfect texture, it's very important to boil marmalade just enough so that it is thick, but not so much that the peel becomes chewy. A thermometer like a fast-reading Thermapen helps judge how far along you are in the cooking process and works perfectly with this recipe and method. The Thermapen is what I use. For a hands-free setup, a probe thermometer with a longer cable like the Thermoworks Dot would be better because then you don't have to hold it with your hands, which would be much less dangerous to use than my hand-held setup.

Frequently asked questions

What to eat with blueberry jam

Blueberry jam is a little unusual in that most people immediately think of strawberry jam and orange marmalade when they think about homemade preserves. I'm here to tell you that blueberry jam is a real treat and very special because it has such a unique, delicate flavour.

If you've ever wondered what to use blueberry jam for, I highly recommend serving it on toast with cream cheese spread thick . Blueberry jam is also great with blue cheese or even goat cheese (if you are a fan). You can also serve blueberry jam with savoury meats, like pork (which is traditionally served with apple sauce).

You can also spoon it over ice cream, like over this cardamom ice cream!

Storage

If you seal the jars properly (by canning them in a boiling water bath for a full 10 minutes or using the inversion method), you can store the closed, sealed jars for a very long time. Most professional jam makers will recommend storing up to 1 year.

Once you open a jar of jam, it should be stored in the refrigerator. Always use a clean spoon or knife to dip into the jar and never double dip to avoid contaminating the jam. If you see mold develop, you compost it or throw it out.

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