Jam Making 101

A few that I saved for eatin’ fresh.


Summer’s Gift
I recently happened into 8 pounds of deliciously ripe, honey sweet Green King figs.  By “happened into” I mean that my neighbor across the hall got a whole bunch of these rare local treats from a tree at his mom’s house somewhere on the east side of Lake Washington.  Green  King figs, when ripe, are never firm under the best of condition;  some of these were firm enough for cutting and eating but many were so soft that they squished under my knife.  They were, is short, some of the most lusciously sweet and sun drenched fruit is is possible to imagine coming from the Puget Sound area.

A few points on making jam
When faced with more pounds of very ripe fruit than two people can possibly eat before it goes off, the obvious course of action is to make jam.  Jam making is very easy, especially on a small scale, and can be broken up into stages so as to avoid the day long jam canning marathons of the kind my mom favored when I was young.

Lets talk about making jam.  It is helpful to remember that  adding sugar to fruit is a way to stop its decomposition.  Once the fruit is boiled with sugar and sealed in a canning jar, it has a shelf life of almost a year.  But since the sugar acts as a preservative just as salt and vinegar do in pickles, it is important to add enough sugar to make sure the fruit will be preserved.

There are 3 major steps in making and preserving jam:
1)  Cooking 2) Setting and 3)  Preserving.
    This sounds pretty simple but there are choices to be made along the way that can have a large impact on the final product.  Cooking is the process by which the fruit and any flavoring elements are combined with the sugar and brought to a stable point.  Setting is the method used to give the jam the preferred consistency.   Finally, Sealing is the means used to remove the jam from contact with air, which extends the shelf life of the finished jam so that it can be enjoyed all year long.

My mom always followed the jam making advice distributed by the US Department of Agriculture, which involved cooking the fruit  with an equal weigh of white sugar,  guaranteeing the set of the jam when necessary by using pectin and sealing the jam in jars with 2 piece lids by  boiling them in water for 15 minutes (she also like to make freezer jam, which is exactly what it sound like, which, for my money, gives a better result than traditional canning).

There are a couple of obvious drawbacks to this method.  1) In the Summer, when many fruits are at their peak and are most reasonably priced, the idea of keeping a cauldron of water boiling for hours on end is not very attractive, especially if you live in a small apartment with imperfect circulation and no air conditioning  2)  Using pectin can not only give an overly gelatinous consistency to the jam, there is something that rankles about making wonderful fresh jam from organic fruit and sugar only to add artificial thickener  3)  Boiling the finished jam for another 15 minutes after it has finished cooking just to seal the jar tends to compromise the fresh flavor of the fruit (The extra cooking time can make the jam seem caramelized or oxidized, when you really just want the flavor of fresh fruit).

Christine Ferber is one of the best known master jam makers in France’s Alsace region, which is known for its wonderful fruit preserves and jams.  In her book Mes Confitures,  she lays out a method for making jam that puts maximum emphasis on preserving the true, fresh flavor of the fruit.  Her method involves using only beautifully ripe,  fresh-picked fruit, only organic ingredients and cooking the fruit as little as possible.  When thickening is required (for fruits with little natural pectin, like cherries), she adds her own home made green apple jelly (outside of quince and lemon rind, green apple has just about the highest levels of pectin of any fruit).  To eliminate further cooking  during the  sealing process, she uses a method that I like to call “inversion”.  Note that my Grandma also favored this method until the 70’s when dire government warnings about improper sterilization forced her to switch.

How Much Sugar?
Like I said, the old way of making jam was to weigh the fruit you want to use, then add to it an equal weigh of refined white sugar.  This assures that your jam will have enough sugar to be properly preserved for long storage.  The problem is that this amount of sugar can make for a very sweet jam.  I find that with most fruits, using 85% of the weight of the fruit in sugar is plenty sweet and also makes for jam with a long shelf life.  The sweeter the fruit, the less sugar is required.  For super sweet figs, as little as 70% works fine.

I also prefer less-refined organic sugar.  I find that organic sugar has less of the “hot” flavor of refined white sugar, which can overpower the flavor of the fruit.  Plus it is less likely to have pesticides and it also less likely to to be GM (that’s a whole story unto itself).  The only downside with less refined sugar is that it is  necessary to skim the jam during boiling a lot more carefully.  This makes sense, because the foam that comes to the top of boiling jam is in fact the impurities from the sugar.  Skimming these impurities out gives a sparkling clear finished jam.  It should be no surprise that less refined sugar has more impurities to be skimmed off.

Skimming the foam off the boiling jam.

Macerating v Cooking
The simplest way to minimize the cooking time for jams is to macerate first.  When fruit is tossed with sugar and left to rest, the sugar begins breaking down the fruit in a way that resembles cooking but without the loss of fresh taste.  Depending of the firmness of the fruit, Ferber recommends macerating the fruit raw with the sugar, or bringing the sugar and fruit to a boil together very briefly then leaving it to macerate overnight.

Figs macerating with sugar before boiling.
A trick for cutting parchment to the right shape.
Boiling briefly with sugar before leaving to macerate overnight.
At the boil.

To Thicken or not to Thicken
Time was people liked a thick jam (heck that still might be today).  If that’s the case, when making jam, one needs to either pick a fruit with enough pectin to yield a nice thick jam or to add some sort of thickener, normally pectin.  One can also add sources of natural pectin, like lemon pith.  Or one can just get good with a looser jam.  In any case, simply boiling the fruit and sugar together will give a certain amount of body to jam.  Further boiling will increase the thickness.  However, you hit a limit where further boiling compromises the flavor of the jam, leaving it tasting “cooked”, “caramelized” or “oxidized”.  So the trick for fresh tasting jam is to test the thickness of the jam after minimum boiling to see if the “set” or thickness, is enough for your taste or if you need to resort to other methods of thickening.  I find that for most fruits, 5-10 minutes of hard boiling gives enough set without compromising the flavor.

Checking the “set” of the cooked jam.

The easiest way to check the set is to put a spoonful of cooked jam onto a cold plate (I keep 2-3 plates in the freezer while making jam for this purpose).  This will allow you to get a clear idea of how thick the jam will be when it cools.  If you are ok with the set, you are ready to seal.  If not, you will need to think about cooking further or adding thickener.

Finished jam ready for jars.

SO whats “Inversion”?
In the typical canning process, the clean jar are filled with hot jam to within about 1/3 of an inch from the top, leaving what is called “head space”.  The jar is then closed with a 2 piece canning lid and boiled in water in  a canner, basically a big pot designed for this purpose, for 15 minutes.  The two piece lid is designed so that during this boiling,  some of the expanding air in the head space escapes.  Then, as the jar cools after boiling, the remaining air in the head space contracts, creating a vacuum that seals the jar.

In the inversion method, the clean jars are filled with hot jam almost to the very top.  The jars are closed with a two piece canning lid, then turned upside down on a towel and left to cool.  The contraction during cooling of both the jam and the small amount of air left in the jar cause the lid to seal.  Easy.

I didn’t tell you to do this!
Let me be clear that the FDA recommends for home canning that one  use the traditional method of sealing jars in boiling water for 15 minutes.  At my restaurants, we don’t can our jam but instead make it fresh each week, so this issue never comes up.  However, at home, when I am making jam just for  myself and my wife, I feel at liberty to use whatever method I like.  After all, the FDA would prefer that I didn’t drink raw milk or eat raw milk cheeses, but I routinely ignore that advice.   However, be aware that sealing by boiling minimizes the risk of food borne illness in canned food.  Full disclosure.

In a nutshell
So there you have it.  The basics of jam making:  Cooking, Setting and Setting, its that easy.  The process varies a little for each fruit, which is where the skill of the jam maker comes in.   You can check out my recipe for Green Fig Jam here.



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5 thoughts on “Jam Making 101”

    1. There are 3 major benifits 1) The shorter cooking time makes for a fresher, more vibrant tasting jam, in short a jam that tastes more like fruit 2) its easier and quicker (not a small thing) and 3) less boiling water time, which is important during hot summer months.

  1. Makes sense. Thanks!

    I would like to pass on my favorite canning tip, though, for boiling water bath — we got an outdoor propane burner w/wok, originally for brewing beer (not in the wok of course; the wok just came with it), but I use it now almost exclusively for canning. It is great — boils a huge amount of water way faster than my old electric stove, plus it means all the heat stays outside. It’s a lifesaver during tomato canning time.

  2. stephanie daugherty

    I moved to Montana and my Ferber book and canning supplies are in storage. I have wild huckleberries to can. I think I can do it based on what you’ve written. Equal parts sugar and berry with a lemon for macerating overnight, then bring bring to room temperature before boiling 5min on stove. In the inversion method, can I put the lids and glass jars on an oven to purify? Or do inbred a water bath?

    1. Yes that sounds about right to me. I typically use slightly less than the weight of the fruit in sugar because i like a less sweet jam. But if your huckleberries are very acidic you might want to use equal weight.

      As for sealing, I sterilize the jars and lids, fill to almost the top with very hot jam, leaving almost no headroom, screw on the caps hand tight, invert on a towel and leave to cool…just that easy.

      If you are worried about sterilization, there are many methods to try but I have never had a problem in home canning just inverting.

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