I know- jam is intimidating. I was scared too. But trust me, if you understand a few key things about making jam it is SO easy and lots of fun to make. At school we probably made some sort of jam, jelly, marmalade or chutney 2-3 times a week so if there's one thing I understand, it's jam.
Let's talk about pectin. Pectin is a naturally occurring substance in fruits and berries which, when heated and combined with sugar, will cause the fruit to 'gel.' It is most concentrated in the pips, cores and skin. Pectin levels vary in different fruits. Citrus fruits, apples and raspberries have a decent amount of pectin in them while fruits such as strawberries, blueberries and blackberries are quite low in pectin. Many people choose to make up for low pectin levels by buying pectin in powder form, however, I personally think this changes the texture and taste of your jam. Another option is to combine the low pectin fruit with a high pectin fruit such as lemon or redcurrant to compensate for the low amount of pectin. Since blueberries have a low amount of pectin, I chose to add lemon juice to this recipe. I also thought the lemon would help to balance the blueberry and thyme flavors.
The second thing to consider when making jam is the amount of sugar you are using. I personally like to keep the sugar on the lower end but if you prefer a sweeter jam, you can add a half of a cup more sugar to this recipe.
Lastly, you need to know that your jam will set when it's cooled in its container. A very easy 'set test' is to put a small plate in your refrigerator before you start making the jam, when the recipe tells you the jam should be set and ready to jar, put a spoon full of the liquid onto your cold plate and put the plate back in the refrigerator. After about 5 minutes, take the plate out and run your finger through the jam. If it wrinkles, the jam will set when cooled. If it is still very liquid, it needs to continue thickening and reducing.
That was your jam crash course. Hopefully you're feeling good about this now and ready to jam it up with me! See recipe below!
Blueberry Thyme and Lemon Jam- makes 3 x 8oz jars
700 grams (approximately 3 cups) fresh blueberries washed, stems removed
3 TBS fresh lemon juice
1 TBS fresh thyme leaves
455 grams (approximately 2 cups) granulated sugar
1. Preheat oven to 350 degrees F. Put small plate in refrigerator for set test.
2. Put jar bottoms in oven to sterilize. Put jar lids in saucepan and cover with water. Bring to a boil to sterilize. Let boil for 5-10 minutes and turn off stove. Lids can sit in the water until ready to use.
3. Measure out sugar in an oven proof jar (I use a pyrex measuring jug) and put in oven with jam jars. The sugar should heat up for approximately 10 minutes. Using hot sugar as opposed to cold with speed up the dissolving process when you add it to the fruit.
4. Put blueberries, thyme and lemon juice in a heavy bottom sauce pan and use a potato masher to mash the berries a bit so they start to break down. Turn on heat to medium. When the juices from the blueberries start to release add in the hot sugar. Bring to the boil and stir continuously.
5. After a couple of minutes of boiling, you will need to 'skim' the top of the boiling liquid using a spoon. You'll notice that a layer of foam will appear on the surface. If you leave this in the jam, your jam will be a bit hazy. The pictures below show the jam pre and post skim.
6. Once skimmed, you're ready for your set test. Take the plate out of the refrigerator and spoon some of the jam onto the center of the plate. Put back in the refrigerator and allow to sit for a few minutes. In the meantime, remove the jars from the oven and prepare your lids and funnel for transferring the jam to jars. Remove the plate from the refrigerator and run your finger through it to see if it wrinkles. It should look like this (note this picture is raspberry not blueberry jam):
7. If the jam is not set, continue to reduce until it thickens a bit more and do another set test. If it is set, start to transfer the jam to your jars using a funnel. Make sure to fill the jam all the way to the top! Enjoy!
Storage note: jam should be okay left at room temperature before opened. Once opened, refrigerate.