Tips for Making Double Batches of Jam

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Making Multiple Batches of Plum Star Anise Jam & Tomato Basil Jam from Food in Jarsdouble batch jam

Our jamming kettles & canners were quite busy the other day as I multi-tasked, something I usually don’t recommend with preserving. However, I needed to do some testing of some new jars and lids that we may add to our line, and I needed to put up some tomato jam for our family.  While getting my tomatoes at our local orchard, some plums & white peaches jumped into my basket. So, I got busy making Marisa McClellan’s Plum Star Anise Jam and my version of her Yellow Tomato Basil Jam. (To hear more recipes from Marisa McClellan register for our meet the author and canning event on August 8th.)Plums

Sometimes, doing multiple batches of preserves isn’t a good thing  – like when you’re using pectin other than Pomona’s, when you have a very finite amount of time in which to complete your canning or when the recipe specifies “do not double”.

However, sometimes multiplying your batch is OK.  If you have the time and if you’re using Pomona’s. It also helps if you have a nice wide jam pot, as it increases your evaporation surface area. My Le Creuset kettles are perfect for this – we use them for all of our preserves. They heat evenly, and the smooth, creamy finish makes stirring and cleanup a breeze. While they are pricey, I was able to get some at a great discount at our local Le Creuset outlet – which is what triggered my discussion with the gals there about doing some canning demos.

An important note when doubling batches: It’s still important to cook your jam down in order to decrease the water content in your end product. The sugar and the evaporation work together to lower the water activity – which plays an important role in pH stability and the shelf life of your preserve. If you double your batch, you can plan on cooking (don’t forget stirring) it more than twice the time of the original recipe. Even though I put both kettles on the stove at the same time, I had my Plum with Star Anise Jam jarred, processed and cooling with time to spare before my tomato jam was ready.  I knew I had the time, so it worked for me.

We’ll be sharing the recipe with their original measurements. I did use a mix of yellow & dark plums and actually tripled the recipe. I love that Marisa uses weights! I’m not great at estimating how much fruit I have – and how much prepared (trimmed, pitted or cored) I’ll end up with.  It’s so much easier to use my kitchen scale as I prepare the fruits. Then I do the math and adjust the amounts for the other ingredients accordingly.

Italian Plum Jam with Star Anise (from Preserving by the Pint) –makes about 2 – 8oz jars

Plum Jam Ingredients

1 pound (460g) Italian Plums – Pitted & Chopped
¾ Cup (150g) granulated sugar
3 Star Anise

  1. Combine the pitted & chopped plums, sugar & star anise in a bowl and let them sit for at least an hour so flavors mingle & juices flow
  2. Gather & prepare your jars (place clean jars in your water bath for preheating) & lids (simmering in a saucepan) and your other tools–funnel, dipper, clean cloth for wiping jar rims, wand for your lids, jar lifter. Plum in kettle
  3. Cook fruit mixture in a wide skillet or kettle over med-high heat, with regular stirring. Bring it to a boil and continue until it bubbles and begins to thicken.  For single batch – about 10 – 12 minutes. If your spatula leaves a void as you stir, the cooking is complete. (I actually tripled mine, so it took about 45 minutes. I could still see the void behind my spatula as it thickened.)
  4. Remove from the heat, funnel into your clean jars leaving ½ inch of headspace, apply lids & bands and process in a boiling water bath for 10 minutes.Lidding Plum Orchard Road
  5. At the end of the 10 minutes, carefully remove them from the water bath, place them on the towel lined countertop.
  6. Let them cool for 24 hours, remove bands & check seals.Orchard Road 8oz Jelly jar Plum Jam

Got a big “Mmmmmmm!” from all of my taste testers!
Jam Tester

Tomato Jam & Basil    (makes about 6 pints)

For my Tomato & Basil Jam, I used the Yellow Tomato & Basil Jam from Food in Jars blog. However, we used reBasil for Tomato Jamd canning tomatoes and doubled the batch.

8 pounds tomatoes; cleaned, cored & chopped
6 cups sugar
1 cup lemon juice
Zest of 2 – 4 lemons (actually only used 2)
½ cup clean, chopped basil

  1. Clean, core and chop tomatoes
  2. Combine tomatoes & sugar in a large non-reactive bowl and let set for at least an hour to allow juices to flow.
  3. Gather & prepare your jars (place clean jars in your water bath for preheating) & lids (simmering in a saucepan) and your other tools –funnel, dipper, clean cloth for wiping jar rims, wand for your lids, jar lifter.
  4. Pour tomato mixture into a large (preferable wide) kettle, add lemon juice & bring to a boil. Tomato Jam bubbling away
  5. Cook for at least 1 hour 15minutes – while stirring regularly. If you have a nice wide kettle, it will likely take another 15 – 30 minutes until it’s cooked down sufficiently.TomatoJam collage
  6. When you’re satisfied with the set, remove from the heat, stir in the basil and ½ of the lemon zest. Taste and add the rest of the zest if you feel it’s required.
  7. Funnel the jam into your clean jars leaving ½ inch of headspace, apply lids & bands and process in a boiling water bath for 10 minutes.
  8. At the end of the 10 minutes, carefully remove them from the water bath, place them on the towel lined countertop.

Let them cool for 24 hours, remove bands & check seals.

Finished Tomato Jam in Orchard Road Wide Pints

To hear more recipes from Marisa McClellan register for our meet the author and canning event on August 8th.

One Comment

  1. Jeany
    Posted July 28, 2015 at 4:30 pm | Permalink

    About thirty years ago, my aunt put up a batch of spiced tomato butter. It was so delicious. She has passed away, and I’ve never been able to find a recipe.

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