If there is a golden rule of jam-making it's this: It's best to turn the fruit into jam as quickly as possible. In this series, we're looking at exactly how to do that. In the first part, we looked at how to select the best fruit for jams. Now we'll look at the tools and techniques that will help you shepherd your lovely fruit into a delectable jam.
The Tools You'll Need
I'm going to take a moment here to make a plug for one of my all-time favorite kitchen tools: the humble food mill. It is kind of a gentler, analog version of a food processor or a blender, and because it's hand-cranked, even in the event of a power outage or the apocalypse, you can still make jam and pizza sauce. See? Totally essential. (Did I mention it can also be used to make spaetzle?)
The most essential piece of equipment for jamming is a very wide, low pot made of a thin layer of conductive metal. This, more than anything else, will help you adhere to that golden rule of speed. The gold-standard jam-pot is made out of copper and manufactured by the French company Mauviel (and yes, it's definitely pricey). Mine came to me as a wedding present and, along with my dog and my guitar, is at the top of my list of things to grab in the event of a house fire.
Copper is great for jam-making because it is highly conductive, which allows for very careful control of temperature. It's also super easy to clean, and, let's face it, it's gorgeous. Once in a while you'll hear someone worried about traces of copper leaching into food from copper cookware and causing metal poisoning. It's not really a concern for jam, for a few reasons. First, the jam isn't cooked long enough for much copper to leach in. Higher risks come from cooking or storing high-acid foods in copper for a very long period of time. Also, unless you're basing your diet around jam (and however tempting that sounds, it doesn't quite qualify as a major food group) any traces of copper in the final product are only getting into your system in teensy and safe amounts. The cooking method is important too: mixing all of your sugar and your fruit together before you put it into the jam pot keeps the acids in the fruit from reacting with the copper.
Until I got my Mauviel jam pot I used a twenty-dollar version I got at the hardware store made out of the same flecked black enamel as my camping dishes, and it worked just fine. The essential feature is that it be very wide to maximize water evaporation and minimize cooking time.
To Chop or Not to Chop
When it comes to cooking jam, most fruit doesn't need much processing. If you're going for a rustic, textured jam with chunks of fruit in it (my favorite kind!), in most cases you can be pretty hands-off. Berries—even strawberries—can be left whole. Apricots can be halved, pitted, and tossed into the pot with no further chopping. If your fruit is dirty or comes from a source where it might have been sprayed and you need to rinse it, be sure to let it dry all the way before proceeding; you are trying to cook all the moisture out as expeditiously as possible, so you don't want to start with any more water than the fruit already contains.
Some fruit, though, can be firm or fibrous and and will therefore need to be processed a little more. Take one of my favorites, Elephant Heart Plums. Even though they are squirty little juice-bombs, they are a pretty sturdy fruit and won't break down quite enough if left too large. For these guys, I like to split the batch of fruit in half: half of it gets quartered and the other half gets cooked gently and then put through the food-mill to make a soft base for the bigger chunks. This method also works well for rhubarb, firm cherries, figs, or anytime you want a jam with a smoother consistency.
The Magic of Macerating
One of my favorite tricks for jam-making is macerating the fruit first. Macerating is the process of coating the fruit in sugar and letting it rest for a few hours or overnight, which pulls some of the juice out of the fruit and creates a syrup with the sugar. I like to avoid putting dry sugar into the jam pot unless my fruit is super juicy, since dry sugar can easily caramelize and burn on the bottom of the pot and ruin the batch. Macerated fruit starts to break down and meld with the sugar, so your jam is already on its way before you even put it over heat.
Cooking the Jam
There are three basic stages of jamming once the fruit/sugar mixture makes it into the pot: the initial heating up and dissolving of any sugar that isn't already dissolved; the rapid bubbling and foaming phase; and the final cooking-down and finishing phase.
During the first phase, you only want to stir the jam enough to prevent scorching. The heat should be low if the sugar is still dry, or medium-high if the sugar is all dissolved already. If the sugar is still dry, you'll need to stir continually until the juices run and the sugar melts. Once all the sugar is melted, you should stir very little or not at all. The less you stir, the faster everything heats up and the moisture cooks off.
Once the fruit mixture has started to boil, some fruit will produce a scum that you should skim off. As a general rule, if there is scum on top that has a dingy color and looks like sea-foam, skim it off with a stainless steel spoon. This scum will make your jam look dull and can even trap dangerous air bubbles in it after canning. The mixture can also bubble up pretty high at this point—I usually try not to fill my jam pot more than a third of the way to allow space for this. Try to stir very minimally at this point; if you are worried about scorching, it's better to turn the heat down a tiny bit than to stir the jam too frequently.
After the foaming has subsided you will notice the bubbling starting to slow down a little bit and appear more glossy. Now is the time to start stirring a little more often, to prevent sticking on the bottom. The best tool for stirring is a sturdy, flat-ended rubber spatula that allows you to feel the bottom of the pot and if anything is sticking to it.
Once the fruit has broken up and the bubbles have slowed, it's time to start testing to see if you've reached the gel point—more about that in part three!