How do I make blueberry jam?

The tested blueberry jam is USDA's Blueberry-Spice Jam: 2 1/2 pints of ripe blueberries crushed, 1 tablespoon of lemon juice, 1/2 teaspoon of nutmeg or cinnamon, 3/4 cup of water, one box of powdered pectin and 5 1/2 cups of sugar, for about 5 half-pints. Blueberries are low in pectin and, by most accounts, short on acid for a good set, which is why the recipe carries both pectin and lemon. This page gives that recipe step by step, a no-pectin spiced blueberry-peach jam, what the sources say about blueberry acid, and why you crush the berries.

Why the lemon is in the recipe

NCHFP lists blueberries with strawberries and cherries as fruits that "contain little pectin" [1], and places them in its "always needs help" band, fruit that always needs added acid, pectin or both [2]. Acid matters to the gel itself: with too little the gel never sets, and with too much it weeps [1]. Pectin gels best at pH 2.8 to 3.3 in jams and jellies, according to Penn State [3].

The sources do not describe blueberry acid the same way, and it is worth knowing where they differ:

This page follows the tested recipe and keeps the lemon. Whatever the berries' own acid, the recipe was tested with that tablespoon in it, and leaving it out changes a tested recipe. The reasons acid helps the set, and when bottled lemon juice matters, are on acid, lemon juice and the set.

USDA Blueberry-Spice Jam

From USDA's Guide 7 [6].

Ingredients

• 2 1/2 pints ripe blueberries
• 1 tablespoon lemon juice
• 1/2 teaspoon ground nutmeg or cinnamon
• 3/4 cup water
• 1 box (1 3/4 ounces) powdered pectin
• 5 1/2 cups sugar

Yield: about 5 half-pints.

Method

1. Have pre-sterilized half-pint jars ready; Guide 7's general jam directions call for pre-sterilized Mason jars [6].
2. Wash and thoroughly crush the blueberries, one layer at a time, in a saucepan.
3. Add the lemon juice, spice and water.
4. Stir in the pectin and bring to a full rolling boil over high heat, stirring frequently.
5. Add the sugar and return to a full rolling boil. Boil hard for 1 minute, stirring constantly.
6. Remove from heat, skim off foam quickly, and fill sterile jars, leaving 1/4 inch headspace.
7. Adjust lids and process.

The recipe itself offers the choice of nutmeg or cinnamon. The broader list of what you may and may not change is on what you can change in a tested recipe.

Crushed, not whole

The recipe crushes the berries one layer at a time. Crushing breaks the skins so the fruit releases juice and pectin into the pot, and it spreads the fruit evenly through the set jam. None of the sources checked for this page has a tested blueberry jam or preserve made with whole berries. If you want a chunkier texture, crush less finely, but crush every layer; a whole-berry spread made by your own method is untested and belongs in the refrigerator, not on the shelf.

Measure in the units the recipe uses. This one is written in pints of whole berries, so measure the berries before you crush them.

No added pectin: spiced blueberry-peach jam

If you would rather not use commercial pectin, NCHFP's spiced blueberry-peach jam sets by cooking down, with peaches for body and lemon for acid [7].

Ingredients: 4 cups chopped or ground peaches (about 4 pounds); 4 cups blueberries (about 1 quart fresh, or two 10-ounce packages unsweetened frozen); 2 tablespoons lemon juice; 1/2 cup water; 5 1/2 cups sugar; 1/2 teaspoon salt; 1 stick cinnamon; 1/2 teaspoon whole cloves; 1/4 teaspoon whole allspice.

Yield: about 6 to 7 half-pints.

Method [7]:

1. Sterilize canning jars and prepare two-piece canning lids according to the manufacturer's directions. Sort and wash fully ripe peaches; peel, pit and chop or grind them. Stem and wash the blueberries, thawing them first if frozen.
2. Combine fruit, lemon juice and water. Cover, bring to a boil, and simmer 10 minutes, stirring now and then.
3. Add sugar and salt and stir well. Add the spices tied in cheesecloth.
4. Boil rapidly, stirring constantly, to 9 degrees F above the boiling point of water, or until the mixture thickens.
5. Remove from heat and take out the spices. Skim, and fill hot jam immediately into hot, sterile jars with 1/4 inch headspace. Wipe the rims with a dampened clean paper towel, adjust lids and process in a boiling water canner.

This recipe gives its target as 9 degrees above boiling, one degree higher than the 8 degrees most NCHFP jams and jellies use. Follow the recipe you are making. How to find the boiling point on your own thermometer is on the temperature test. Use yellow peaches only; white peaches are not safe for canning, as explained on peach jam.

Processing blueberry jam

That is the USDA chart for Blueberry-Spice Jam, in sterilized jars, and the same 5, 10 and 15 minutes are USDA's times for jams without added pectin [6]. The NC State copy of the spiced blueberry-peach jam prints no time of its own [7], so use this chart for it. Because blueberries are low in pectin, sterilize: NCHFP prefers sterile jars "especially when fruits are low in pectin," since the longer process needed for unsterilized jars can weaken the gel [1]. How to sterilize, and the altitude addition for it, are on do you need to sterilize jars.

Selling blueberry jam

Blueberry is a federal Group I fruit, so a product sold as blueberry jam needs at least 47 parts fruit to 55 parts sugar and at least 65 percent soluble solids [8]. Adding spice is fine under the standard. Reducing sugar below the standard changes what you may call it; see what you can call your jam.

Wild cousins of the blueberry

Huckleberries are the blueberry's wild relative in the Northwest and the northern Rockies, and they have their own tested recipes with lemon, on huckleberry jam. If your blueberry jam is soft after a day or two, the USDA remake procedure is on jam that didn't set.

References

1. National Center for Home Food Preservation, General Information on Canning Jams, Jellies, and Marmalades, accessed October 2026. https://nchfp.uga.edu/how/make-jam-jelly/jams-jellies-general-information/general-information-on-canning-jams-jellies-and-marmalades/
2. National Center for Home Food Preservation, Jellied Product Ingredients, accessed October 2026. https://nchfp.uga.edu/how/make-jam-jelly/jams-jellies-general-information/jellied-product-ingredients/
3. Penn State Extension, LaBorde, Food for Profit: Commercial Production of Jams, Jellies, and Fruit Butters, updated May 24, 2024. https://extension.psu.edu/food-for-profit-commercial-production-of-jams-jellies-and-fruit-butters
4. Pomona's Universal Pectin, Create Your Own Recipe: Developing or Converting Recipes for Cooked Jam or Jelly Using Pomona's Pectin, modified August 24, 2023. https://pomonapectin.com/?p=21164
5. University of Wisconsin Extension, Ingham, Making Jams, Jellies & Fruit Preserves (B2909), undated. https://iowa.extension.wisc.edu/files/2021/08/Making-Jams-Jellies-Fruit-Preserves-B2909.pdf
6. USDA, Complete Guide to Home Canning, Guide 7: Preparing and Canning Jams and Jellies (Blueberry-Spice Jam), rev. 2015. https://nchfp.uga.edu/papers/guide/GUIDE07_HomeCan_rev0715.pdf
7. NC State Extension (copy of NCHFP recipes), Preserving Blueberries: Recipes from NCHFP (Spiced Blueberry-Peach Jam), 2015. https://foodsafety.ces.ncsu.edu/wp-content/uploads/2015/09/Preserving-Blueberries-Recipes-from-NCFHP.pdf
8. U.S. Code of Federal Regulations, 21 CFR 150.160, Canned fruit preserves and jams (Cornell LII text, current). https://www.law.cornell.edu/cfr/text/21/150.160