Glass Jars for Jam, Jellies and Chutneys

Raspberry jam



Jam jars need to be very clean. To sterilize glass jam jars, wash in soapy water, rinse well and then place in a cool oven - 250F for 15-20 minutes.

Preserving with sugar and acids inhibit growth of the microorganisms which cause food to rot. Jams and jellies set because of the action of pectin, a substance in fruit that, when cooked with sugar and acid (from the fruit), thickens and gels the preserve. In chutneys the main preserving agent is vinegar. Chutneys are usually made with vegetables, although orchard fruits are also used. Always take care when preparing jams and chutneys to do as the recipe states and sterilize and prepare equipment as directed to minimize the risk of food poisoning.

Types of jams

A traditional jam is fruit cooked, usually to a pulp, with sugar to set. Sometimes the fruit is cooked to a pulp and then sieved before the sugar is added to get rid of excessive pips. A jelly is fruit cooked, usually with water, to a pulp. It is then dripped through a bag and the resulting juice (not pulp) is simmered with sugar until setting point is reached. A conserve could loosely be described as a very rich type of jam, sometimes with the addition of alcohol. Usually the whole fruit - raspberries, strawberries, blackcurrants, etc. - are preserved in a heavy syrup rather than being cooked to a pulp.


Successful Jam Making

  • Always use fruit that is in peak condition, preferably slightly under ripe - the pectin content will be at its best. Over-ripe or damaged fruit is not ideal - the pectin has begun to change to pectose and the jam will not set well. The result is likely to deteriorate rapidly.
  • Use the correct amount of sugar as indicated. The sugar reacts with the pectin to set the jam.
  • Strawberries The amount of sugar you need depends on the amount of pectin in a fruit, but generally, the fruit to sugar ratio for traditional jams is 450g (1lb) sugar to 450g (1lb) fruit. The sugar content is sometimes a little higher or lower depending on pectin and acid content. Very acidic fruits such as blackcurrants have good pectin content - these can take an extra 50 to 100g of sugar to get a really juicy jam. Fruit such as strawberry - lower in pectin, but also much sweeter - can take the usual amount or possibly a little less.
  • Use coarse-grain sugar such as preserving or granulated - this ensures a good clear jam. Coarse grains dissolve more slowly and evenly giving a better result. Fine sugars dissolve less easily and are usually more expensive too.
  • Don't add water when cooking fruits already high in sugar, such as strawberries, raspberries and blackberries.
  • Don't over boil the preserve. Once the sugar is added it usually takes a fairly short period of time to reach setting point, as long as the pectin content is good. To test for setting, put a spoonful of the jam on a cool plate and put into the fridge for a few minutes. After that time the jam or jelly will form a wrinkly skin if it is ready.
  • Always cover the jam immediately it has been poured into the jars as this gives a good seal and prevents mildew appearing on the surface.
  • Always store preserves in a cool, dry area, away from direct sunlight, and use within the year.

Know the pectin content of the fruit used - the higher the pectin content, the better the set. If you use fruit with a low pectin content, try adding some fruit with high pectin content such as apples, damsons or redcurrants to give a good result. Alternatively, commercial pectin can be added to low-pectin fruits to ensure a good set. Pectin is best added to the fruit before the addition of the sugar.

High-pectin fruits: blackcurrants, redcurrants, cooking apples, damsons, quinces, gooseberries and some plums.

Low-pectin fruits: blackberries, cherries, elderberries, pears, rhubarb, strawberries and medlars.