Plum Jam

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It's plum season, in the San Francisco Bay Area.  This past winter gave us a slight respite from our years of ongoing drought, and the fruit trees have been celebrating.  Last year, our plum tree bore almost no fruit at all.  I doubt we got more than two dozen fruits, all together.

Not only are my trees laden with fruit, but I'm lucky enough to have friends who want to share their bounty.  Both DJ and Terrence invited me over to their yards, and let me pick surplus fruit from their trees.

They've both got trees that produce tiny plums.  One of the things about having fruit in an urban area, is that folks don't tend to know the variety of fruit in their yards, because they weren't the ones who planted the trees.  I believe these are cherry or myrobalan plums.  They have burgundy leaves, and are planted widely as an urban street tree.  Because they produce (and drop) massive amounts of fruit, these trees are not universally beloved.  So, picking friends' fruit is a classic win-win situation.  I get fruit, I give them some of the jam that I've made, and they don't have as much of a sticky mess to deal with at the end of the fruit season.

These are my plums.  I'm pretty certain that they are Sant Rosa plums, mostly because they are the most common backyard variety around here.  They are truly delicious, with a complexity that shames supermarket fruit.

The difference in size between the two varieties is remarkable.

I cut up my plums, so that they would cook at about the same rate as the smaller plums.  In later batches of jam, I started the larger plums first, and then added the smaller ones. I don't remove the skins or pits, because it's just too much work.  Skins dissolve, and I sieve out the pits later in the process.

Robb and I go to a lot of estate sales, which is where we found this lovely cooper jam pot.  When cooking in a copper lined pot, many recipes advise cooks to add sugar at the same time as the fruit. Apparently, the ph level of the sugar keeps copper from leaching into the jam.  That seems prudent.  No point poisoning our friends.

I always feel like I'm drowning my fruit in sugar, when I first add it to the mix.  Sugar is essential to preservation and texture.  But the volume never fails to freak me out.

Sometimes I think I should start a blog of photos of circular cooking photos.  Another photo of another pot...

The purpose of this pan is to have as much surface area as possible, in order to facilitate evaporation.  It's a great size, because it doesn't allow me to go insane and try to make excessively large batches.  I simply cannot scale-up jam recipes. Once I go above a certain volume, I fail at gelling.  

I really need to better understand the science of pectin.  I've read tons of cookbooks and articles, and they're infuriatingly contradictory, with questionable science crashing into folk wisdom.

When the smaller plums slip from their skins, and start to look translucent, I ladle them into our chinoise, in order to sieve out the pits.

Would anyone reading this blog be at all surprised to learn that Robb and I watch a lot of shows about the history of cooking.  We are both in love with Ivan Day.  (Seriously, there are shows we watch just for his segments.)

One of the great pleasures of cooked plums is their beautiful translucency.  When food is so beautiful, sieving out the pits can still be fun.

At this point, I'm just cooking until the jam sets. I keep a stack of ceramic saucers in the freezer, and spoon hot jam onto a cold plate.  The cold plate quick-chills the jam, and gives a sense of the ultimate texture.  (I'm convinced that one of these days the contrast of temperature  is going to shatter one of these saucers.  Which are all from the 1930s and 1940s.  Of course.  I'm such a freak.)

This is also the time that I fine-tune the flavor, adding a bit more sugar and lemon juice as needed.

I made three batches of plum-based jam, two with cherry plums and one with pluots from our tree.  Let's hope it lasts until Christmas-time.