Strawberry Jam
Basic how-to, with variations + a handy list of fruit and their pectin content.
Strawberry jam is the vanilla ice cream of preserves: It’s the number one most purchased flavor in America (I’m assuming the number one most homemade). Like vanilla, people also think it’s boring, but there are so many varieties of strawberries to preserve (check farmer’s markets) and things you can add to the recipe, such as herbs or black pepper, making strawberry jam far more interesting than the Smucker’s I grew up with.
Here’s a quick, straightforward jam recipe which is set only with naturally occurring pectin, and some variations like strawberry-red wine (see photos below) to get you started on your own ideas. Read on to find a link to the National Center for Home Food Preservation if you want to read more in-depth about jam processing.
Note: beware of fruit sold in some markets as “jam fruit” or “pie fruit”; it’s often fruit that is overripe, and therefore has less pectin (although you can mix some of it in to your total weight of jam fruit as long as you have underripe fruit as well).
Here’s how to preserve fruit in one sentence: Cook fruit* with sugar and acid in a ratio of 1000g fruit : 600g sugar : 2 Tbs lemon juice** to 221ºf. That’s it! To get more details, scroll down for list of fruit broken down into high, medium, and low amounts of natural pectin and acid.
RECIPE
Strawberry Jam, Yields about 4 cups
• 1000g / 35 ounces strawberries, with 25% slightly underripe
• 600g / 21 ounces sugar
• 4 Tbs lemon juice
Have your sterilized jars and lids ready, as well as a preserving funnel if the mouths of the jars are narrow, plus some clean kitchen towels and a dampened towel. It’s a good idea to have some ice water nearby in case of burns if you are not experienced in preserving. Jam burns are really painful!
Hull the berries by using a paring knife to cut the green tops off. Depending on the texture you prefer, you can either slice or mash the berries.
Combine the berries (sliced or mashed), sugar, and lemon juice in a large, heavy bottomed pot. The volume will increase when it first starts to boil, so you need to plan for extra headroom. Cook on medium first to dissolve the sugar. Increase heat to high and cook at a rolling boil. Skim the froth off of the top from time to time. The mixture will bubble less vigorously as it approaches 200ºf. Keep stirring to avoid the berries from sticking to the bottom of the pot and scorching.
Closely watch the temperature; it will take awhile to get above 200ºf; once it gets to around 215ºf, it will get to 221ºf quickly. Turn the heat off once it gets to 219ºf; it will carry over cook to 221ºf.
Fill jars with a ladle, leaving 1/4” headspace. Depending on the type of jars you’re using, a funnel may be useful. Wipe off spills on the rims with a clean dampened towel. Put lids on immediately and process in a hot water bath for 10 minutes, with 2-inches of water above the jar lids. Start timing the sterilization once the water in the hot water bath is boiling. If you are only processing a few jars, it’s not necessary to use a large canning pot, but place a rack in the bottom of the pot to ensure the boiling water fully circulates around the jars.
Strawberry-Red Wine variation
•Add 240ml / 1 C red wine to the berries, sugar, and lemon juice. Cook to 221ºf as usual. It will take a little bit longer due to the extra volume of liquid.
If you are at an altitude of 1000 feet or more, add 1 minute of processing time for each 1000 feet of altitude
Here is an excellent source of information from the National Center for Home Food Preservation for more detailed information.
MORE ON FRUIT AND PECTIN:
The variables you’re dealing with are the levels of natural pectin (a water-soluble fiber) and acid in a fruit and how to choose fruit that will give you the best result (i.e. either choosing high pectin/acid fruit, or combining low pectin/acid fruit with fruit that have higher amounts so that you get a proper set).
On fruit and pectin: The riper the fruit, the less pectin it contains, so make sure that you have around 25% underripe fruit in the mix. Pectin also requires the presence of an acid to gel, and most people use lemon juice, although citric acid can be used as well. If you are using fruit that has less pectin in it (see list below), add a little more acid to help activate it. A good rule of thumb is 2 Tbs lemon juice per 1000g fruit for higher pectin fruit, and 4 Tbs for lower pectin fruit.
On sugar: Pectin in fruit is activated when you have heat + acid + sugar in the right ratios. There’s a lot of flexibility; sugar has to make up just over half of the weight of fruit in order to activate its pectin. Yes, it can be less, but the jam will have a more caramelized flavor as you cook it down to evaporate enough moisture to thicken it.
The amount of sugar can vary from 55% to 150% or more, but you wouldn’t want to go that high because you’d end up with a little fruit suspended in sugar syrup. A lot of American recipes use a 1:1 ratio of fruit to sugar, but that’s too high for my taste. I usually settle on 1000g fruit : 600g sugar, or 60%.
On added pectin:
Pectin is added for 3 reasons. It’s either because the fruit being preserved doesn’t contain enough to gel on its own, you want a higher yield, or you want a “juicier,” less “cooked” flavor or color.
Strawberries are a good example of a fruit that changes a lot depending on how long it’s cooked, from bright red to dark brown. Apricots, too, will go from a bright, golden hue to a darker, almost apple butter color when cooked for a long time. You will also get a higher yield with added pectin because it acts almost immediately after mixing it in, whereas when you cook fruit and rely on natural pectin, you have to cook out a lot of moisture and reduce the volume of liquid before it naturally gels.
On heat:
Overheating will break down pectin’s ability to set, and under heating will prevent it from activating. (Overheating isn’t usually an issue, unless you’ve over cooked the preserve, added water to thin it, and cooked it again. This method of recovery can work, but I’ve also ruined batches.) Best to watch the thermometer like a hawk once it gets to 215ºf, as it can go above quickly. Don’t get bogged down on this point or over-think it, as it’s unusual to run into this problem.
* cored, hulled, sliced, diced, peeled, mashed etc. See list for high and low pectin fruit.
**the amount of lemon juice added can vary between 2 and 4 Tbs, depending on how much natrual pectin the fruit you are using has in it. Consult the list below for levels of pectin and acid each fruit contains and adjust quantity accordingly
Fruit naturally HIGHER in pectin and acid: Sour apples and crabapples, cranberries, gooseberries, plums (choose underripe), quince, currants, blackcurrants, damson plums, grapefruit, lemons, limes, red currants, white currants, passion fruit (if cooking shell to extract pectin).
Fruit with a MEDIUM amount of pectin and acid: Apricots, grapes, loganberry, medlar (low acid), blackberries, loganberries, blueberries, navel oranges, tangerines, sweet apples, blueberries, raspberries, boysenberries, Morello cherries, unripe grapes, greengage plums (high acidity), mulberries, plums (ripe), tayberries
Fruit with LOWER natural pectin and acid: Sweet cherries, figs, melons, grapes (western Concord), guavas, nectarines, peaches, pears, Italian plums, strawberries, rhubarb (high acidity), elderberries, pineapple, loquats, wild blackberries, ripe grapes, kiwi, mangos, passion fruit (pulp only), pumpkin
