Jam update: How I went wrong and a recipe for peach-plum jam

A while back I wrote about making blueberry jam with maple syrup and lemon zest, but I have learned much about jam-making since then and I must confess that I was wrong. The basic recipe is just fine, but it turns out my technique could use a lot of improvement.

Now, you ask me, "Tora, how did you find out you were wrong? What should we be doing differently?"

Well, about two weeks ago (I think it was two weeks ago), Mike, Sebastian, and I decided we would go to Borders and see if we could find anything good at the going-out-of-business sale. We don't usually pick over scraps of dying stores like vultures, but it's a book store. If there was a 10-step program for book addiction, we might be candidates for it.

As we looked around, Mike found a book that he thought I might like: The Blue Chair Jam Cookbook by Rachel Saunders. This charming, lovely book is probably all you will ever need to become a master jam/jelly/marmalade maker. It has gorgeous photos, lots of great information about techniques, and recipes that range from the utterly simply and sublime to the complex and sophisticated. And within about 10 minutes of sitting down to read, I discovered that I have been doing it wrong. So, let me explain my mistakes and pass on some of my new-found knowledge to you.

1. I've been using the wrong kind of pot. Ideally, you should use a copper pan that's 11 inches at the base, 15 inches at the rim, and 5 inches high with a 11- to 12-quart capacity. Now, copper pans are not currently in my budget, as dearly as I would love to have one. What I gleaned from this information is that I need a lot more surface area. So I broke out my stock pot, which is definitely deep enough and has a 10-inch diameter. Not perfect, but I've already gotten better results. (If anyone feels especially generous, a copper pan would be a much appreciated Christmas gift.)
2. I've been using the wrong application of heat. Instead of low and slow, I should be cooking this stuff hot and fast to keep as much of the fruit's flavor and texture intact. The correct way to do it is to heat the mixture of fruit and sugar slowly at first, just until it starts to bubble and release a lot of juice, and then crank up the heat to get it up to a pretty fierce boil. What you are trying to accomplish is a lot of evaporation (which explains why you need a lot of surface area in your pan). While it cooks, you need to keep stirring frequently, both to aid evaporation and to ensure that the jam doesn't stick to the bottom and burn. Note that this will be extremely messy.
3. My testing for doneness has a lot to be desired. Rachel Saunders suggests doing this instead: Place a saucer with five metal spoons in the freezer. When you are ready to test your jam for doneness, take your pot off the heat, transfer a small amount of jam to one of the frozen spoons and return it to the freezer for a minute or two. When the bottom of the spoon feels neither hot nor cold, inspect the sample in the spoon. It shouldn't run but sort of clump up in a jelly-like blob on the spoon. If it doesn't, discard test spoon 1 and put the pot back on the heat for another five minutes or so and test again. The cooking process for jam (there are differences for jelly and marmalade, so be aware of that) will take about 15-30 minutes tops. 
4. I like her method of preparing the jars for preservation, but I am still not completely sold on it. Usually, I would transfer jam to hot sterilized jars that I have boiled, place the lids on them, and boil them for another 15 minutes. She recommends sterilizing the washed jars in a 250-degree oven for at least 30 minutes, adding the jam, closing the jars, and placing them back in the oven for another 15 minutes. It's a lot easier method than boiling the jars, but so far, every batch I have made this way has had at least one jar that didn't seal. Of course, that means I get to try the jam right away, which is great, but it rankles a little bit. 
5. The last clear technique difference is her method of flavoring the jam with herbs. I like to wrap up my herbs in a piece of cheesecloth and let it boil in the jam, whereas she prefers to add sprigs and let them steep in the hot jam for a few minutes after cooking and then fish them out. I haven't made up my mind on this one yet. I tried her method, adding some basil to a recent batch of plum-peach jam after it had cooked, but although the basil was extraordinarily fragrant (from my garden!), I can't taste it in the jam at all. So I will probably experiment a bit more before making my decision one way or another. 

I've applied these modifications to three recent batches of jam—blackberry with lemon verbena, peach-plum with basil, and my blueberry with maple syrup and lemon—and I am definitely getting better results. The texture is better, the flavor is brighter, and the set is much better. I also love that I can get a jam in a lot less time. What's a bit of drag is that the yield seems to be a bit smaller, but I can live with that to get awesome jam. Here's a recipe for a jam experiment I tried with plums and peaches. The flavor is beautiful: bright, fruity, a little tangy, basically everything you get from a really good peach or plum eaten while dripping over a sink at the height of summer.  

Peach-plum jam with basil  

Yields about four eight-ounce jars 

• 500 grams peaches, peeled, cut into 1-inch pieces (discard the stones)
• 500 grams plums, cut into quarters (discard the stones) (any kind of plum will probably work for this, but I used red plums, which created a dark red jam; just be mindful that if you use, for example, greengages, the color may not be very pretty)
• 6 deciliters sugar
• juice from two lemons
• 4-5 basil stems (optional, but nice)

1. Background prep: Place a saucer with five metal spoons in the freezer, and sterilize your jars using whatever technique you prefer (keep them hot as you make the jam).
2. Layer the fruit and sugar in your jam pot (starting and ending with a layer of sugar).
3. Let the fruit-sugar mixture sit for at least an hour, up to overnight (refrigerate if you want to do this).
4. Add the lemon juice.
5. Heat the mixture slowly until the fruit produces a lot of juice, and it has started to bubble. 
6. Bring the heat up to high and stir continually to keep the jam from burning. Expect copious amounts of steam and a lot of spatter. If you have an apron, this would be a good time to wear it. (I really need to get one of those.)
7. Cook at high heat for about 15 minutes (skim off the foam).
8. Test for doneness: Take the pot off the heat, get a sample of jam from the pot and transfer it to a frozen spoon. Place the sample in the freezer for a minute or two. Touch the bottom of the spoon, if it's neither hot nor cold, it's time to inspect the doneness of the jam. It should not run, but be gelatinous. If it runs, put the jam back on the heat for another five minutes and test again. Keep testing until you reach doneness.
9. When the jam is done, take it off the heat and add your basil sprigs and let it sit for five to 10 minutes. Then remove the basil and pour the hot jam into your hot jars (be sure to leave at least an inch at the top) and sterilize them, using a hot water bath or oven as you prefer. 
10. When you let the jars cool, you will hear little popping noises as they create a vacuum seal. If one of the jars doesn't seal (you can tell if you can depress the lid with your finger and it pops up again), just let it cool and enjoy it right away. The rest will be good for several months. 

A note on cooling: Don't move jam around a lot while it cools. One of the things it does as it cools is creates a sort of lattice structure. If you disturb that structure while it's forming, the jam won't set very well (or possibly at all).

Update: Check out the National Center for Home Food Preservation for more information about keeping your jams and jellies safe.