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When my friend Sandy recently brought me 10 lbs. of freshly picked Michigan blueberries, I was planning to can my annual batch of blueberry jam. But, I got a great tip from my sister Nelda to try making blueberry butter in a slow cooker instead. I make apple butter in a slow cooker in the fall, so why not blueberry butter in the summer? Great idea, Sis!

Although it takes longer to cook (um, that why it's called a slow cooker), most of the time is hands-off. Like apple butter, blueberry butter doesn't contain any actual dairy butter at all. It is an old-fashioned way to preserve fruit that dates back hundreds of years. The slow cooking time concentrates and thickens pureed, sweetened blueberries that are flavored with spices (cinnamon & nutmeg), brightened with lemon juice and zest, and cooked longer than traditional jam until the blueberries caramelize, thicken, and darken. There is less added sugar in butters vs. jams, so this blueberry butter isn't quite as sweet as blueberry jam.

In addition to my sister, I got inspiration for this recipe from Marisa at Food In Jars.

Can it. This is a big batch recipe that is suitable for water-process canning. I'll explain how. My 10 lbs. of blueberries yielded two batches of this recipe for blueberry butter and filled 18 half-pint mason jars (9 jars in each batch). 

It's versatile.

• Use it as a spread on toast, bagels, biscuits, pancakes or waffles.
• Stir it into oatmeal, yogurt, or smoothies.

It's giftable! Jars of blueberry butter make great homemade gifts. Printable labels are provided further down in this post.

Step-by-step photos for making
Slow Cooker Blueberry Butter

Step 1. Assemble the ingredients

• blueberries -- I prefer fresh over frozen, but both will work.
• white and brown sugar
• lemon juice and zest -- to brighten the flavor
• spices -- cinnamon and nutmeg

Step 2. Add the blueberries to a slow cooker, cover, and cook undisturbed on high for 90 minutes. This will soften the blueberries so they are easier to blend.

Step 3. Add sugars, lemon, and spices; stir.

Step 4. Use an immersion blender to puree blueberries to desired texture. I like mine with a few tiny bits of blueberries still visible. (Alternatively, transfer mixture to a blender, puree, and return to slow cooker.)

Step 5. Cook uncovered on high for 5-6 hours until thickened and darkened, stirring frequently to prevent scorching. I use a whisk for stirring to remove any thickened lumps that form around the edges.

Here is a visual of the thickness of the sauce when it is finished:

Click here to see it in action

Click to pause

Step 6. THICKNESS TEST. While the blueberry butter cooks, place 2-3 small plates in the freezer. When it appears to be thick enough, put a spoonful of the hot mixture on a chilled plate. Run your finger through it. If the gap runs back together quickly, it needs to cook longer. Continue cooking and test it again in 30 minutes. Repeat this until the gap on the plate runs together very slowly. Your blueberry butter is done! 

When your butter passes the thickness test, lower the slow cooker temperature to warm and cover it while you prepare the canner and jars. 

CANNING BLUEBERRY BUTTER (Water Processing)

• Adhere to canning safety guidelines. It's important to follow the jar preparation and processing recommended by the USDA. If you want more detailed canning information, I recommend the Ball website. They are the ultimate authority, and their site is loaded with detailed information and recipes suited for canning. 
• For general canning tips, see my previous post,

Step-By-Step Canning Tips

1. Prepare the jars & lids. I use half-pint jars for blueberry butter, but you may also use pint jars. Wash the jars in hot sudsy water, rinse and dry them. The jars don't have to be sterilized, since the filled jars will be processed for 15 minutes (as per new canning guidelines from Ball). The washed jars need to be hot when they're filled with hot butter. Keep the jars hot in the canner filled with simmering water. Or, my preference is to put them on a tray in an 180 degree oven to keep them hot until it's time to fill them. I think that's easier than juggling them in and out of hot water right before filling them.

The lids and rings should be washed in hot sudsy water, rinsed and dried. The lids do not have to be kept hot in simmering water according to new canning guidelines. 

2. Fill the jars. Use a canning funnel and ladle to fill each hot jar with hot jam, leaving 1/2" headspace. 

3. Insert a bubble remover down the side of the jar and pull toward the center to release any bubbles (you can use any long, thin object like a chopstick).

4. Clean jar rims thoroughly with a wet paper towel. If the rims are dirty the jars won't seal.

5. Add a lid to each jar. Screw on a ring until it is "finger tight".

view on Amazon:  mason jars, canning funnel, large ladle, bubble remover & headspace tool

CANNER TIPS:

• I'm using the Ball Electric Canner in these photos. If you do a lot of canning, I highly recommend it; it's worth the price!
• If you don't have a canner, any large pot of boiling water with a rack in the bottom will work as long as it's deep enough to allow for 1" of water above the jars when they are inside.

6. Use a jar lifter to lower each jar vertically into the canner of boiling water. There should be at least 1" of water over the tops of the jars.  Cover and return water to a rolling boil. Process jars in boiling water for 15 minutes (20 minutes for quart jars). Turn off the heat and remove the lid; leave the jars in the hot water for 5 more minutes.

view on Amazon:    

• electric waterbath canner, pictured below (highly recommended for serious canners)
• stove-top waterbath canner and utensil kit (economical option--I used this for many years)
• jar lifter

7. Use a jar lifter to remove each jar vertically and set on a towel. (I line a sheet pan with a towel in case I need to move the jars without disturbing them.) Leave undisturbed for 12 hours. Within 30 minutes after the jars are removed from the water, you know they've safely sealed if the center of the jar is slightly indented (it shouldn't give when you press it); often you'll hear a popping noise when they seal. If any of your jars don't seal, store them in the fridge and use them within 2 months, or freeze them for up to 6 months.

The blueberry butter is ready to enjoy now or store to use throughout the year! As you can see in the photo below, the butter thickens more during the water processing and becomes a perfect spreadable consistency.

For a finishing touch, I like to label my jars. That way they're easy to identify on my shelf, look attractive on the table, and are ready for gift-giving, too. This blueberry butter will be universally loved and fun to share. Going to a party? Grab one of these to take as a perfect host/hostess gift. Need a little something for a teacher, co-worker, or neighbor? You can't go wrong with a jar of blueberry butter. Print the labels and stick them on the sides or lids of each jar--easy!

Download printable jar labels/tags. These are sized to fit on jar lids (regular or wide mouth) or sides.

• Print these on card stock, cut them out, punch a hole on top, and hang them from the jar neck with a ribbon, string, or rubber band. OR
• Print them on sticker paper and stick them to the jar or lid. (This is what I do.) Or, print them on regular paper and stick them on with tape.

If you don't have a printer or specialty papers, you can have a store with printing services download and print them for you (Office Depot, Staples, etc.)

Cut with scissors or a circle punch. You can cut the round tags out carefully with scissors, or use a circle punch to make the task easier and more precise. I use a 2-1/4" circle punch; it fits both regular and wide canning lids.

view on Amazon:  2-1/4" circle punch (this fits mason jar lids)

Click on the image below to download & print a full sheet of labels/tags. 

The biggest benefit of canning blueberry butter is that you can enjoy it all year long and share it with others, too.

Here are more of my recipes that are suitable for water process canning:

• Classic Marinara Sauce
• Roasted Salsa
• Roasted Salsa Verde
• 3 Barbecue Sauces
• Pickled Jalapeno Peppers
• Fruit & Applesauce Blends
• Choose-Your-Stone-Fruit Jam
• Choose-Your-Berry-Jam
• Bread and Butter Pickles
• Dill Pickles
• Pickled Garlic
• Slow Cooker Apple Butter
• Apple Cider Syrup

Make it a Yummy day!

Monica

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Slow Cooker Blueberry Butter

By Monica              Servings: makes 8-9 half-pints

Ingredients

• 14 cups (4-5 lbs) blueberries
• 1 3/4 cups granulated white sugar
• 1 3/4 cups brown sugar
• 1 lemon, zested and juiced
• 1 tablespoon ground cinnamon
• 3/4 teaspoon ground nutmeg

Directions

Put 2 or 3 small plates in the freezer to use later for checking thickness of butter.

Wash and drain blueberries. Add to slow cooker. Cover and cook on high 90 minutes.

Remove lid, stir, add remaining ingredients. Use an immersion blender to puree. (Or, transfer to blender, puree, and return to slow cooker.)

Cook uncovered on high for 5-6 hours, until reduced, thickened, and darkened, stirring frequently to prevent scorching. Stir with whisk to smooth any lumps as it cooks.

TO TEST FOR RIGHT THICKNESS, remove a small plate from freezer, put a spoonful of hot mixture on chilled plate and return it to freezer for 2 minutes. Remove from freezer, run your finger through the center of the mixture to make a gap. If the gap runs back together quickly, continue cooking for another 30 minutes and check again on a chilled plate, repeating until the gap runs together very slowly; the mixture is ready for canning. Lower the slow cooker to warm and cover while preparing jars and canner.

FOR WATER PROCESS CANNING: Add hot blueberry butter to hot jars leaving 1/2" of headspace. Water process in water canner 15 minutes for pints & half pints, 20 minutes for quarts. Turn off heat, remove lid, and leave jars in hot water for 5 minutes. Remove from canner and let rest undisturbed for 12-24 hours. Store jars in dark, cool place for 1 year or longer.

FOR CANNING SAFETY:
--Follow jar preparation and processing recommended by the USDA; see canning safety guidelines at http://www.freshpreserving.com

FOR GENERAL CANNING TIPS go to www.theyummylife.com/canning_tips

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