Jam Making Rules

As strawberry season begins here in Malta, it feels like the start of summer jam making season too. And although I firmly believe Wexford strawberries are the best, Malta does pretty lovely ones as well. Every year I say I’m going to make jam just like my mother did and as my father still does. And every year I end up not making jam the old fashioned way but my quick trick way with chai seeds. Although its lovely its not traditional jam making. So I decided I would have a good think about it this year and check out my mothers old recipes, hints and tips. According to her cookery notes, a well made jam should, set properly, have a good colour, be clear (if its a jelly jam), have good balance of flavour and keep well. My father makes jam every year and it lasts for 2 years maybe more depending on the jam. Imagine the money you could save! I came across these “rules” for making jam in her old Cookery Notes book, issued by the Department of Agriculture & Fisheries costing 1 shelling back in the day. So thought I’d share them for anyone thinking about making jam as well as some other notes I have.

They key part of jam making is of course the “Pectin” which enables the setting of the jam. Its a gum-like substance usually found in the coarse part of the fruit such as the skin, pips and core. The acid in fruit draws out the pectin when cooking. However if you have fruit low in pectin or acid such as strawberries, you will need to add the pectin and acid. Fruits high in pectin and acid such citrus fruit, apples, gooseberries and plums shouldn’t need anything added.

General rules of jam makingPrep, Fruit & cooking

  • Choose firm, ripe or slightly under-ripe fruit as over-ripe fruit contains less pectin and will not set correctly.
  • Check if your fruit is in the high or low pectin category of fruit or if you will need to add pectin & acid. Here is a quick table
Pectin Rich FruitFruit With Medium Pectin Low Pectin
Crab apples, cooking apples, black & red currants, damsons, gooseberries, citrus fruit, plumsApricots, blackberries, loganberries, raspberries, Pears, ripe cherries, strawberries, blueberries, peaches
Pectin & acid rating for some fruits popular in jam making.
  • Prepare your fruit correctly.
Hard skinned& citrus fruitBerries, soft & stoned fruitApples & PearsPeaches & Apricots
Washed, dried, chopped/ sliced. Juiced and piped for marmaladeStalks removed, washed in a colander, stones removedPeeled, cored, sliced or quarteredPeeled, halved, stoned removed. stone kernels may be added to give flavour to the jam.
Quick prep table for fruits in jam making
  • A wide shallow preserving pan is best to ensure proper evaporation and boiling. Pans can be greased lightly to prevent the jam from sticking.
  • The pan should never be more than half full to allow the jam to boil vigorously and avoid undue evaporation.
  • Simmer before sugar! As sugar has a hardening effect, the general rule is to allow the fruit to gently simmer until tender before adding to ensure the fruit is cooked thoroughly. The sugar should be added slowly and allowed to dissolve over a low heat. Once its all dissolved then the mixture is returned to a rapid boil. Ideally warming the sugar before adding. If you do not follow this step, then you risk the sugar crystalizing in the jam.
  • Good quality ideally jam sugar will reduce the amount of “scum” rising on the fruit. So use a good sugar. White granulated sugar dissolves quickly. The amount of sugar you will need wil also depend on the fruit and its acid content. So it is usual to allow about 1lb of sugar for each 1lb of fruit. Smaller amounts are used for fruits such as strawberries due to to the low pectin ratio. Higher amounts will be used for things like gooseberries and high pectin fruits. So sticking to a recipe is good when you are starting out. Too much and you can risk crystallization and too little will impair the longevity of your jam.

  • Have some glycerine to hand, as a teaspoon of it will reduce the amount of “scum” when added to boiling jam.
  • Do not remove the scum until the jam is nearly cooked. It is wasteful to skim too much. There is also no need to stir continuously.


  • Test jam in good time to avoid it overcooking and loosing its flavour as well as darkening in colour. If it is under-boiled it will not set in addition to having a much shorter shelf life. Testing can be done in various ways as follows:
    1. Put two teaspoonful’s of jam on a cold plate. leave for 2 minutes. If the surface of skin crinkles when touched, the jam has reached setting point. When testing this way, make sure to lower the heat on your pan until the test is complete. (my mum used this method)
    2. Dip a clean wooden spoon in the jam & lift out. Allow the jam on the spoon to cool. Tilt the spoon and if the jam has reached setting point it will fall off in flakes.
    3. Use a sugar thermometer; at 220°F the jam will have reached setting point. To check its reading correctly, when placed in boiling water it should register 212°F
  • Jam jars should be spotlessly clean, washed in warm soapy water, dried in the oven and warm for potting
  • When the jam is set, remove any scum. Give it a last stir & pot immediately, filling the jars to the top, allowing for shrinkage when cooling. When filling the jam, put a clean metal or silver spoon in the jar to prevent the glass breaking.
  • Cover straight away with a wax disk, some cellophane and your jar lid.
  • Wipe with a damp warm cloth before labelling and dating your jar.
  • Store in a cool, dark well ventilated cupboard or pantry.

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