It’s perfectly fine to use frozen fruit for jamming! Remember to measure the fruit while still frozen & firm, then thaw to crush.
Active time: 20-30 minutes
Total time: 70 min
Yield: 3 cups/750 ml, approx.

Ingredients

2 cups red currants, destemmed (ok if the occasional tiny stem remains)
2 cups pitted whole sour cherries
1 cup small, or quartered, hulled strawberries
1/2 cup granulated sugar

Instructions

In a large saucepan or dutch oven, at least 10/25cm dia., crush the fruit. I like to use a potato masher. Avoid using a food processor, as the motorized blades tend to crush the seeds, and the resulting jam tastes seedy”.
Add the sugar, stirring to dissolve.
Set the mixture aside for at least 30 minutes, or up to overnight. This is called macerating, and allows the juices from the fruit to combine with the sugar. Cover the pan to keep out bugs and dust.
This next step is OPTIONAL, but I prefer my jam mostly seedless. Crush the fruit mixture a bit more with the masher, then push the mixture though a medium mesh sieve to remove the seeds. Return the now smooth fruit/sugar mixture to the saucepan.
Heat the mixture over high heat, stirring occasionally, until it comes to a boil. Reduce heat slightly, to maintain a (not too violent) boil. Cook the mixture, stirring occasionally, until very thick. A spoon drawn across the bottom of the pan should leave a trail, into which the mixture does not flow immediately.
Remove from heat, and let stand 5 minutes without stirring. Stir the mixture to distribute fruit, and then ladle into clean containers. Cool and then cover and store your jam in the fridge, for up to 1 month.
For longer term storage, process the jam using standard water-bath canning procedure, for minimum 10 minutes.

Home Canning for High-Acid Foods

Introduction

Home canning is not complicated. It is a simple procedure that applies heat to food in a closed glass jar to interrupt the natural decaying that would otherwise take place. The air we breathe and all foods in their natural state contain microorganisms, such as molds, yeasts, bacteria and enzymes. Food spoils when these factors are not controlled. Proper, safe home canning procedures control the growth of spoilage microorganisms allowing us to keep food beyond its normal storage period.

Heating the filled jars is the only way to change the atmospheric pressure, thus creating a vacuum seal that will keep your treasured contents safe.

The heat processing method, according to up-to-date tested home canning guidelines includes:

Placing prepared food in mason jars that can be sealed airtight with a two-piece metal SNAP ® LID closures.
Using the correct type of canner to heat the filled jars to a designated temperature for the food being processed.
Maintaining this temperature for the time specified in up-do-date, tested recipes to destroy spoilage mircoorganisms, inactive enzymes and properly vent air from jars.
Cooling jars properly to allow lids to form a strong vacuum seal

Use only current, tested home canning recipes that:

Include the appropriate heat processing method and time for the food and mason jar size.
Designate head space for the food and jar size.
Come from reputable source that uses the jars and lids that you are using today.

You will need:

Only the best, top quality ingredients. For best results, preserve ingredients at it’s peak of freshness.
A currant, tested home canning recipe.
Mason Jars
Two-piece SNAP LID ® closures
Large, deep, non-reactive pot to prepare recipe (i.e. stainless steel or glass)
A water-bath canner OR large deep pot, at least 3/8 cm deeper than the jars you are using.
Rack or folded towel for bottom of canning pot
Common kitchen utensils – measuring spoons and cups, long handled spoons and spatulas, funnel, a ladle or handled cup to transfer recipe to jars.
A place to set filled jars after processing: area on the counter away from drafts, and where jars can remain undisturbed for several hours. Protect the warm jars from thermal shock by placing a folded towel or newspaper on the counter first.