Team building, cooking events, catering, parties, and classes in the San Francisco Bay Area

Strawberry Jamming

Making your own strawberry jam is so easy, it's almost a shame to buy it. Especially since we have such great strawberries in the market, organic and sweet. Yes, we'll still have them for a while — it's not too late for this year. My recipe is very flexible. You can make a large or a small batch, and if you follow the basic formula, you'll have a perfect product. I do it two ways — If I'm working, for instance, with a group that's making brunch, we'll make a small batch in the microwave. You need only a Pyrex 8 cup mixing bowl and something to stir with — no canning, just refrigerate what you don't use right away and it will keep, in a jar or plastic container, for a long time.

For making enough to last a while (or give as gifts), you need to use a pot, and make sure it's a stainless steel one not aluminum, please (not sure about the anodized aluminum, that may be OK, but regular aluminum will leach into the mix and make it metallic flavored). Helpful to have a candy thermometer, as hitting the magic 220°F. mark assures perfect jam, but not having one is no deterrent. If you make a lot, you need canning jars and a big pot to process them in. I've had my old speckled enamel canning pot for 40 or so years, but any large pot will do. You just want to be able to cover the jars by two inches with water, and not have them knocking together as they process. A towel in the bottom of the pot, and if you need it, another tea towel wound between the jars will make it certain you don't break any. 


The formula:

  • One pound berries = 2 cups, stemmed and crushed
  • Use an equal measure of sugar, and a tablespoon lemon juice per cup of berries
  • Add a tiny bit of butter to the pot, maybe 1/8 tsp. See why below.
  • So, for one pound berries, 2 cups sugar and 2 tablespoons lemon juice. The batch in the photos was made with 3 pounds of berries. 
  • Each pound of berries will yield 1 1/2 pints of jam. 

I am always careful not to waste, so cut the green tops from my berries carefuly, rather than slashing across and discarding too much fruit. Make sure, of course, that they are well washed first! And,  trim away any bad spots. Do use fresh berries, not the ones from the back of the fridge — that bit of mold might ruin your batch. 



Crush the berries well with a potato masher, place in a heavy pot. Add the sugar and lemon, and stir over medium-low heat to dissolve the sugar. Then raise the heat, and continue to cook until the fruit is thick.  If you put a tiny pinch of butter in — I forgot this, at first and you can see the results, I almost overflowed the pot — it will keep the cooking fruit down where it belongs. My batch of jam took 45 minutes to get to 220°F., but a small batch in the microwave will only take 10 minutes. How do you know (if you don't have that thermometer) it's done? Take a bit and put it on a room-temperature plate, and let stand for a minute. If the jam is thick enough, it won't run. If it runs after resting a minute, continue for a few more minutes. It does get very much thicker when cold.



To can: you want washed and well-rinsed canning jars, new seals (the flat piece) and bails (rings) to tighten the jars that are not dinged up (but needn't be new). The seals and even extra bails, you can buy in the hardware store, if you're re-using jars. The seals are really only good for one canning so if in doubt, replace them. Put the jars (not the seals) into your pot of boiling water. You want them hot when you pour in the jam, to make sure you don't crack your jars. Remember, the jam is HOTTER than boiling water. 


Two other pieces of equiment that make your life easier: A canning jar lifter (see the picture) and a wide-necked funnel meant for canning, which will keep the jars from getting jam all over the tops, which might prevent sealing.

When your jam is cooked, drain the water from the jars and lay on a towel. Fill to 1/4 inch below the top. Do NOT go fuller, or you won't get a seal. Put the sealing ring on, then the bail. Tighten these fairly gently — so they're firmly in place, but not impossible to get back off. Gently put the jars back in the water bath, with 2 inches water above the jars. Simmer for 10 minutes, covered. When you lift the jars out, the sealing ring may still be slightly domed, but it will pop into place as they cool, but it might take a few hours. If it doesn't, maybe you forgot to clean a bit of jam from the edge of the jar, or have a bad ring. Use that jar of jam first, and refrigerate it. The sealed jars will keep for years if you forget to use them or give them away. But you won't, will you?