Tonight on Big Allotment Challenge our contestant are asked to make two jars of jam, one savoury and one sweet and boy do they struggle!
While jam making is most usually a summer pastime when soft fruits like raspberries, strawberries or orchard fruit like plums and apricots are at their best, provided you stick to some simple rules you can make jars of delicious jam at any time of year.

Don’t be phased by the lengthy instructions below a quick read through and you set to go.

A jam is a set fruit preserve. By set I mean a preserve that mounds on a spoon, one that sits comfortably on a scone and one that does not drip from your breakfast toast. A set is achieved when fruit plus acid, sugar and pectin in the right proportions are cooked to a temperature and concentration that allows the formation of a colloidal bond. So essentially when the fruit is boiled with these three ingredients in the correct quantities the jam will set.

So the question is: How do we go about getting the right mix? This is not as daunting as it sounds, many fruit are high in pectin and also high in acid so sugar is the only part of the equation that needs to be added.

Let’s start with the fruit. My first rule is that only perfect fruit should be used for jam. You are preserving an illusive flavour, you will work hard to make sure the jam is balanced and correctly set, why then would you want the final taste to be of slightly mouldy berries?Avoid at all cost fruit labelled “For Jam” this is often over ripe and beginning to soften or rot. For a chutney, a jelly or even a fruit cheese you can cut away the bad parts and continue, but for jam you must use the best quality fruit you can find. Berries with a rich colour and perfume but very slightly under ripe are best. Firm fragrant plums, apricots that still only just give when gently squeezed and figs that have not split at the base are all excellent.

For the acid part of the equation you must think about how sharp the fruit is. Sharp as lemon juice? No need then to add more acid. But if the fruit is palatable and sweet to taste them you will need to increase the acidity to achieve that all important set, so add lemon juice if necessary.

This leaves us with sugar. For a set jam the quantity of sugar is dictated by the quantity of fruit on an equal basis. Low sugar jams are looser in texture and must be stored in the fridge.I favour granulated sugar for the simply reason that it is the least expensive. I’ve used it in all my recipes for many years and have yet to find an issue with it. If I need to add pectin to a jam then I’m happy to use “Jam sugar” which has pectin ready added, a ready mixed sugar/pectin combination.

It is really important that you weigh your ingredients carefully, as a general rule I use equal quantities of prepared fruit and sugar adding acid and pectin as necessary. To test for a set: Turn off the heat and make your first test, take a plate from the freezer and drop a spoonful of jam onto it. Leave for about 1 minute then push the side of the mixture gently with the tip of your finger and look at the surface. If it wrinkles the jam is ready, if not turn the heat back on and boil for a further two minutes before testing again. Always turn off the heat while testing for a set.

Raspberry jam is a great jam to start with as you only need fruit and sugar and thawed frozen fruit works as well as fresh picked berries.