Dirty Business: Preserving Blueberries

Between our own bushes, and the excursions that Mrs. Butcher and I have taken to harvest the bushes on the island from our canoe, we had about 1.5 gallons of berries and still counting.  However, the first berries we harvested were starting to get a little soft, so it was time to do the first batch of preserves.  I decided to do a double batch at one time because I had enough berries to do it.  That was a mistake.  Even with my largest pot, the berries foamed over the top twice and made a huge mess.  So, lesson learned.

For those of you who haven’t done any boiling water canning before, here’s a nice little primer, with a relatively simple recipe.  Before we get into the recipe, however, we have to address the first and most important part of canning:  sterilization.  We’re going to make a shelf-stable preserve so we don’t have to take up a ton of refrigerator space for the next year.  That means it is vital that our tools and jars are as clean as possible. 

Let’s start with the tools.  For ease and simplicity, a good basic set of canning tools includes the following:

A large, deep pot with either a screen at the bottom or a canning pot with a cage to keep the jars off the bottom.

A tool for grabbing jars.

A magnet for grabbing lids.

A tool for measuring headspace in the jars and getting rid of any air bubbles in the preserves.

A wide-mouth funnel.

Most grocery stores will sell canning kits that will include everything but the pot:

The tool on the far right is the one for measuring headspace in the jars and for removing air bubbles.  Those little steps on the bottom are in ¼” increments.  The tool next to that is the magnet for grabbing lids.  Wash the headspace tool and the funnel in hot, soapy water and allow to air dry.  Likewise, wash your canning jars and lids in hot soapy water.

Fill your pot around ¾ of the way with water and place your canning jars and lids inside.  Place a thermometer on the edge of the pot so it reaches the water and set on high heat.  You’ll need the thermometer to monitor the temperature of the water to know exactly when to pull the lids out.  The lids have an outer ring with a sealant compound which will soften when the water reaches 180 degrees.  However, if you allow the lids to stay in the water until it boils, then the compound will break down and will not seal properly later.  Allow the jars to stay in the boiling water to sterilize.

While all this is happening, you can get going on the blueberries.  Here’s the recipe for a single batch:

10 Cups Fresh Blueberries

5 ½ Cups Sugar

¼ tsp. Salt

2 Tbsp. Lemon Zest, grated

1/3 Cup Lemon Juice

You will notice that there is no pectin in this recipe.  That is because pectin is for the morally bankrupt.  We’re going to cook these preserves down enough so that they thicken on their own—which also means they will have more flavor concentrated in that reduction.

Wash the blueberries and pick out any debris, like stems or leaves.  Place half the berries in a pot and mash well with a potato masher.

Add the other half of the whole berries, sugar, salt and lemon zest and mix well.  Place the pot over medium heat, cover and stir every few minutes.

Once the blueberries come to a low boil, remove the cover and continue to stir every five minutes.  If the blueberries start to stick at all, then stir more often.  IMPORTANT:  as the berries cook down, they will start to boil more violently every time you stir them.  They will even spit out over and outside the pot.  So, make sure you are using the longest spoon you have, and are stirring gently.  From my years in the food business, I can attest that getting molten sugar splattered on your skin is not a pleasant experience.  Cook for about 25 minutes as a starting point.  In the meantime, place a small dish in the freezer—this will be used to test the doneness of the preserves.

After 25 minutes, the berries should have reduced by roughly half, and are feeling thick.  Pull the plate out of the freezer and place a small amount of the berries on the plate to sit for a minute.  Then tilt the plate and see how they behave.  If the berries run freely down the plate and separate from each other, then they aren’t ready yet and should keep cooking.

Because I was cooking a double batch it took almost an hour for mine to get ready. 

Once the preserves are thick enough, add the lemon juice and cook for an additional five minutes.

Place a cooling rack next to the pot of preserves, and pull one jar out of the boiling water and place on the rack.  Using the funnel, fill the jar until there is a ¼” of headspace between the preserves and the rim of the jar.

Headspace is one of those important factors in canning.  The ideal measurement is different depending on what is being preserved and the objective is to provide less space than is needed for bacteria to grow.

Remove the funnel and, using opposite end of the headspace tool, run it down the inside of the jar along the glass to release any air bubbles that might have been trapped. Gently wipe the rim and threads of the jar with a clean cloth, then—using the magnet—place a lid on top, then screw a ring over the lid until it is just finger tight.  There’s no need to crank the ring as tightly as possible—the pressure from the canning process will take care of that.

Place that jar back in the pot then grab the next jar and repeat the process.  One jar out, one jar in until you’ve filled all the jars.  Depending on your yield, you may have some preserves that don’t fill the jar all the way.  Don’t place that last jar in the water—just place it in the refrigerator and be sure to eat it within the next few weeks.

Make sure there is at least two inches of water above the tops of the jars in the canning pot.  Once the water has returned to a full boil, allow everything to cook for 10 minutes.  Then, using the jar tongs, remove each jar to the cooling rack. 

Here is another critical point in the process.  LEAVE THE JARS ALONE.  Do not immediately start writing dates on the lids or otherwise messing with them.  They need to sit and cool on their own until the lids start to pop downward as the air in the headspace cools enough.  This is what creates the final seal for the jars to make them safe for storage.  DO NOT PUSH THE LIDS DOWN YOURSELF–I DON’T CARE WHAT MARTHA STEWART SAYS.  It shouldn’t take more than 15 minutes for all the lids to pop down.  If any don’t seal properly, then just place those in the fridge.

Once everything is cool, then feel free to label or date as you see fit.  These preserves can last on the shelf for upwards of a year as long as they are stored in a cool, dark place.