Strawberry Jam

 

Ingredients and Equipment

4 to 6 pint baskets (1 half-flat) of fresh ripe strawberries. Peak of season [SF bay area]: May 20+/-.
1 lemon for each basket of strawberries, plus 2 more
Sugar equal to the weight of the strawberries plus the juice of the lemons:

4 baskets = @ 3.25 lbs.
6 baskets = @ 4.5 lbs

Canning jars, rings and lids approximately 1 per pound of strawberries, plus one.
preserve kettle
pressure cooker
hot-jar tong
magnet, lid lifter
canning funnel
tongs
wooden spoon
ladle
potato masher
kitchen scale

Secrets and Hints

Wear safety glasses and do not work in bare feet. Boiling hot sugar sputters when mixed and burns badly!

Weigh the prepared fruit and juice and use an equal amount of sugar by weight as opposed to using an equal volume of sugar to fruit. Do not reduce the amount of sugar because you want a healthier jam. It will not work and if you are that concerned about your health don't eat jam.

Remove the light pink scum (not the translucent bubbles) as it arises. This will help keep the pot from boiling over if you have a small pot or are processing a large batch in a preserve kettle.

Use a preserve kettle. It is designed (wider at the top than at the bottom) to minimize boiling over and maximize reduction.

The best thing is to forget the juice that is lost during skimming. If you wish to retain this and return it to the pot, skim into a sive over a saucepan on a low heat so that when the serup is returned to the pot it does not lower the temperature.

Crush about half of the strawberries. This produces a smoother jam but also releases pectin from the fruit.

Sterilize the jars in the pressure cooker beginning when you begin processing the fruit. The jars and lids can then be removed from the hot water, filled, sealed, and when all the jars are ready (not as each jar is ready) returned to the water for the final 6 minute hot water bath. In any case be aware that bringing a large quantity of water to a boil in a cast-aluminum pressure cooker takes a good while! You don't want the filled jars to sit around getting cool before being given the hot water bath.

The Formūla

Steralize the jars. Place the jars, lids, and rings in the pressure-cooker and cover with water, close the lid (you do not need to seal the lid, just closed will do) and turn the heat to high. When you hear the jars jumping around reduce the heat to low; return the heat to high at the time you begin timing the cooking of the jam.

Clean the lemons.

Juice the lemons retaining the rinds and putting the juice (about 1 cup) in the preserve kettle.

Remove any seeds from the half-rinds, and cut off the ends and put them to one side.

Clean the strawberries.

Cut off the leaf-end and cut into bits placing them in the preserve kettle.

Mash about half the strawberries with a potato masher. I prefer to mash the whole lot. This might be made easier with one of these hand-held electric mixers.

Pour the strawberry/lemon juice mixture into a bowl on the kitchen scale. Be sure to 'tare' (set the scale to zero including the bowl) the scale first! And note the weight.

Pour the fruit back into the preserve kettle.

Using another clean, dry bowl, tare the scale again with this bowl and measure out a weight of sugar equal to the weight of the fruit.

Pour the sugar into the preserve kettle.

Put the lemon rinds into the preserve kettle.

Turn on the heat to medium-low, stir the mixture until it is liquid and gradually raise the heat to high.

Begin timing the boil at the point where the mixture begins a rolling boil, at the first point at which the boil does not subside when the mixture is stirred.

Stir, skim the scum, and watch the heat to be sure the thing doesn't boil over. If the pot threatens to boil over reduce the heat just enough to bring down the boil and return it immediately to high when it is safe to do so. You want to keep the heat as consistantly high as possible.

Boil at as high a continuous temperature as possible, stirring to prevent burning and skimming. More reliable than using time for the measure of doneness (the degree of thickness ideal for jam) is to use a candy thermometer and stop the cooking only when the mixture reches 220°F.

When the jam has reached the proper temperature, quickly remove the kettle from the heat.

Remove the last bits of scum.

Remove the lemon rinds with the tongs squeezing out any of the good juice. Disgard the rinds. (Depending on the variety and thickess of the rind, some people regard this as a candy.)

Remove jars, lids and rings one set at a time from the pressure cooker and fill them to just below the canning funnel.

Be sure to place the lids on properly and tighten down the rings just finger-tight. Too tight will cause a broken seal. Too loose will cause a broken seal.

Fill all the jars.

The Hot Water Bath. Place all the jars back into the water in the pressure cooker, close the lid cook for 6-10 minutes.

Remove the jars from the hot water bath.

Listen for the 'click' of the button on the lids as the cooling air under the lid creates a vacuum which seals the lid and comrpresses the button. Visually check to see that all the buttons are compressed. Press the button with your finger: if it 'clicks' it has not been compressed and the jar is not properly sealed. If one is not compressed, refrigerate that one and use it first.

Properly sealed jam can be stored in a cool dark place for up to a year, sometimes longer.