Sunday, September 21, 2014

Fall Rhubarb and Crabapple Pectin

Rhubarb is one of the first plants up in the spring, with it's beefy red stalks ready to eat by the time the first strawberries are coming in.  One of the hallmarks of late spring-early summer for us has always been making rhubarb jam, rhubarb crisp, rhubarb cake, and so on.  But does it have to be just a spring treat?  Established plants can produce good 'barb all summer long, and if it's picked at the end of the summer, or even (gasp!) in the early fall (thanks, Mom!), delectable new combination jams and pies can be had for the effort.  One such jam we were keen to try, which may have been related to our present bounty of crab apples, was a rhubarb-crab apple jam.  Plus, we wanted to try our hand at making some pectin from the crab apples, and another batch of jam seemed like a good excuse.

First things first...let's make some pectin!  Start by putting about 12 cups of crab apples in a pot and just covering them with water.  No need to core or de-stem them, just check for bugs if they make you queasy.  Boil the heck out of them (make holy apples?), until they're real soft.  It took about an hour on our stove.

Then we hit 'em hard with the stick blender to make a crab apple sauce, which we filtered with the ol' t-shirt inside a strainer inside a bowl trick.  They say not to squeeze the filter because it can make the pectin solution cloudy, which can make the resulting jelly cloudy.  But we always make jam, which is cloudy anyway.  Guess who's getting a bear hug!

The resulting liquid is pink (and a little cloudy), and kind of sweet-tart, like a crab apple-flavored lemonade.

We tested it's strength by putting a teaspoon of it in a tablespoon of rubbing alcohol, as described here.  The pectin isn't soluble in alcohols, so it precipitates out to make a gel that can be picked up with a fork if the pectin is concentrated enough (like in the picture).  Don't eat it!

Timeout for some food chemistry!  (See here for more info.)  The pectin we're making will be high-methoxyl pectin (as is pretty much all pectin when it's first made, regardless of whether it comes from apples or citrus peels).  The pectin structure is a long chain of galactose molecules (G), which each have a carboxylic acid group (C) off to one side (galactouronic acid).  Most of those acid groups are actually in the methyl ester form, which some food scientist back in the day decided to call methoxyls (M). (Never mind that a methoxyl is a different kind of functional group to every other type of chemist.)  The chains of galactose molecules (and the "C" groups, to some extent) can form a three-dimensional hydrogen bonding (H-bond) network, provided there's not too much water (W) around.  That's what makes the 'gel' part of jelly.  Water interferes with that H-bond network, so a ton of sugar (S) is added as sort of a 'pectin body guard.'  The sugar also interacts with the pectin and the water, but keeps the water from interfering too much with pectin's H-bonding.  The gelling reaction is also pH-dependent, because below a certain pH, the "C" groups become protonated and don't repel each other.  But if the pH is too low, the G-units start to fall apart.  Talk about a finicky reaction!

If high-methoxyl pectin is treated with acid under specific conditions, some of those methoxyl groups are converted to carboxylic acid groups, which have quite an affinity for cations like calcium (Ca2+).  With enough calcium around, the pectin chains agglomerate mainly because of calcium's ability to attract two chains apiece.  Pomona's pectin is low-methoxyl, which is why you can get away with lower and multiple types of sugars, and also why it comes with a packet of CaCl2.  Taking high-methoxy pectin to low-methoxy pectin could probably be done at home, but it's a tricky process because the same acid that can break off the methoxyls can break apart the bonds holding the galactose molecules together.

Now, on to the jam!  We had a little less than 4 cups rhubarb pulp (shown in the pot), which we combined with enough crab apple sauce (from another set of crab apples that we removed the seeds and stems from!) to total 5 cups of fruit pulp.  This site says to generally use 4-6 tablespoons pectin per 1 cup fruit juice, then combine those volumes and use that volume of sugar.  So 5 cups fruit pulp times 4 tablespoons equals 20 Tablespoons = 1.25 cups pectin solution, which means 5 + 1.25 = 6.25 cups sugar.  Remember: low-sugar pectin, this is not.  Then we made the jam just like with a package of sure-jell: combine the fruit pulp and pectin, bring to full rolling boil.  Add sugar, return to full rolling boil.  Boil one minute, pour into jars...

...and pour any extra into a bowl for sampling as soon as it's cool enough to not burn your tongue.  Hey, look!  It kind of worked!  It's a little runnier than it looks in the picture because a skin formed on the top, but it's plenty thick enough for our purposes. 

The rest of the pectin goes in jars in the fridge for another batch of jam or just as a crab apple-ade drink.  Or maybe a pink Metamucil.  Not bad on it's own, especially considering all the health benefits of pectin, which a form of soluble dietary fiber.  We're going to be *so* regular!  The chickens are currently enjoying the filtered pulp, and hopefully getting some health benefits, too.

Do you eat rhubarb in the fall, too?  Have you ever made your own pectin?  Let us know in the comments section below!


  1. Any idea how well this would work with wild grapes?

    1. You could definitely replace the rhubarb part with grapes, but I'm not sure how efficient making the pectin from grapes would be. I think some grapes have high levels of pectin, but my impression is that generally they're lower in pectin than apples or crab apples.

      I guess if you really want to know, you'd have to try it! Boil some grapes up like we did with the crabapples, and see how strong the filtrate is with the alcohol test. If it's not strong enough, keep boiling until enough water boils off that the pectin is sufficiently concentrated.

      If you'll end up with a pint instead of three quarts, and you'll have your answer. :-)

  2. Pectin in jam has a great effect on its thickness. There are numerous health benefits to it as well.