Best-ever plum jam

Here’s how to do it – tips galore!

Jam is best made in small batches because a small batch will cook down and reach setting point more quickly than a big one. A short cooking time preserves the taste, colour and texture of fruit.

Fruit

Although you might think jam is a perfect home for ripe fruit falling off the tree, slightly under ripe firm fruit with a nice natural bloom is best for jam making because it has more pectin. Fruits which are naturally low in pectin, such as strawberries, benefit being paired with other fruits that are high in pectin, such as apples, or with organic or homemade fruit pectin (I’ve never tried making the latter, but there are plenty of recipes online for this, and it would be handy when making strawberry jam). Lemon juice will also help the set because it helps extract pectin from the fruit. It also helps preserve the colour of the fruit and adds a sometimes-missing fresh zing.

The stones from plums and other stonefruit can be put in a square of muslin, tied with string, and added to the fruit in the pan to extract extra flavour and pectin. Remove before adding the sugar. If stones are hard to remove from fruit, leave them in and skim them out later as they float to the top during boiling.

A little water added to the pan stops the fruit from catching on the bottom of the pan before juice starts running. Some fruits require more water than others, and some, like strawberries which squish down easily, require none. If the recipe calls for water, put it in the pan first, then dump the fruit on top. If you do it the other way around, the water might not filter through the fruit in time and fruit may catch on the bottom. Burnt fruit makes terrible jam.

I like my jam to have pieces of visible fruit rather than a smooth homogenised texture. If you want smooth jam, chop fruit finely. I usually cut medium-sized plums in half and large ones into quarters.

Cooking fruit gently to soften it before adding sugar will ensure skins remain tender, and thereafter the jam need not be boiled for as long to reach setting point. Shorter cooking produces jam with a brighter colour and fresher flavour (prolonged boiling can turn jam muddy-coloured and it may lose its bright fresh fruit flavours).

I do not like to use pectin in my jams, and see no need to, as I prefer a natural product made the old fashioned way by cooking fruit and sugar together until they reach setting point. It’s not complicated, only made to seem so by companies wanting to sell us pectin and pectin products.

Some people worry about the bubbly scum on top of jam, and others don’t. If you want to remove it, take pan off the heat and skim it with a slotted spoon, or gently stir it through the jam. An old fashioned trick is to swirl a small knob of butter over the surface of the jam to dissolve the scum.

Sugar

Sugar helps preserve jam and prevent mould forming on top. If mould forms on top of homemade jam just scrape it off – it’s harmless – and thereafter keep the jam refrigerated. I cannot vouch for commercially made jam.

Use granulated sugar in jam making. It’s cheaper than caster sugar (superfine granulated), and doesn’t throw off as much scum. By all means use organic sugar but be aware that dark sugars can turn jams an unappealing brown colour. Do not use ‘jam sugar’ as it has pectin added to it. Plum jam does not require pectin to set.

Most jams call for equal proportions of fruit and sugar, although this varies. Is the fruit weighed before or after stones are removed? Does it really matter? Best practice is to weigh after removing stones just in case it throws the balance out, but I’ve done it both ways, usually because I forget, and it doesn’t seem to ruin the jam.

A good tip is to heat the sugar before adding it to the cooking fruit because cold sugar will slow down the bubbling and it will take longer to bring it back to a boil and to reach the point of setting. The longer you boil jam, the higher the chance there is of it loosing its nice bright colour. Let the bubbling subside before adding the sugar, stir carefully until it is completely dissolved, then bring it back to a rapid boil. The jam should cook at a brisk boil but should not look like an exploding Mt Vesuvius.

Flavourings such as citrus peel, fresh or crystallised ginger, bay leaves, kaffir lime leaves, coriander seeds, cinnamon quills and the like, can be added at the beginning of cooking. More delicate ingredients such as seeds scraped from a vanilla pod, and alcohol such as rum or sherry, should be added once the jam is removed from the heat, just before putting the jam in jars.

Equipment

I know aluminium pans are frowned on, but they do make great jam pans because aluminium is such a great conductor of heat. Copper is ideal, but expensive. Stainless steel is an option. Do not attempt making jam in a regular straight-sided saucepan, unless you have a very wide roomy pan; once the fruit and sugar boil up, you’ll be surprised to see how high the jam rises in the pan. Sloping sides help speed the reduction of the jam. I’m kind of attached to my aluminium jam pan because it is as old as Methusela – well, at least my parents and grandparents used it!

Once the jam is transferred to jars, put the preserving pan in the sink and add all the utensils and other bits and bobs you have used and fill the pan with hot soapy water. Leave to soak for 10 minutes – the sticky jam will dissolve – then rinse everything, dry and pack away until next time.

A long handled wooden spoon for stirring is essential – a metal implement will heat up and you’ll feel the burn! Wear gloves by all means.

A jam jar funnel is a great help when ladling bubbling jam into jars. It fits inside the mouth of the jar, leaving rims clean. Always leave a little headspace at the top of each jar, rather than filling the jar to the top as you do with brine and pickling liquids.

If you are using a thermometer, always warm it in a jug of hand-hot water before putting it into a pan of bubbling jam. The temperature rises quickly on a thermometer, but the last degree or two usually takes some minutes to attain. As soon as the jam is at setting point (104°C / 220°F), remove the thermometer, put it back in the jug of water and let it soak until the jam has dissolved before rinsing, drying, and putting it away somewhere safe. I bought my thermometer in London decades ago – if looked after carefully, they can last a lifetime.

You can also test for setting using the following simple age-old method. Have a couple of saucers chilling in the fridge. When you think the jam might be ready, take the pan off the heat – if it continues boiling it may well overcook and lose fresh taste and colour.

Put a small smear of jam on one of the chilled saucers and leave until cool. Run your finger through the middle of the jam. If setting point is reached the jam will wrinkle. If it’s not ready, reheat the jam and bubble for a few minutes more, repeating the test.

If you’ve put the jam into jars and notice that it hasn’t set, you can store it in the fridge and use it up quickly, or put it back in the pan, reboil it and check for setting point. You’ll need to wash and sterilise the jars again before use.

Jars

Always have more jars ready than you think you are going to need because it is such a hassle to run short of a jar or two. Select the jars you are going to use checking there are no chips on the rims and that the lids are in perfect condition. You can recycle jars used for other preserves, but you will not be able to use any tops that smell vinegary or spicy.

To prepare jars, first wash them in hot soapy water. Rinse thoroughly, drain on a clean cloth then dry. If you are using a lot of jars, put them in a shallow roasting tin or similar to make it easier to remove them from the oven. Transfer to a cold oven and heat it to 110°C / 225°F. Leave the jars in the oven for 30 minutes.

Wash, rinse and dry any tops. If there are metal bands, these can go in the oven; do not put anything with a seal into the oven or it may melt! Many cooks still use the old-fashioned method of covering jars with discs of cellophane and securing these with rubber bands. The cellophane shrinks as the jam cools, making an airtight seal around the rim of the jar. It’s effective and cheap.

Prep your bench by lining it with a few layers of newspaper and cover it with a clean cloth or paper towels; the newspaper will protect your bench and allow the jam to cool slowly and evenly.

Bang jars twice on the newspaper to remove big air bubbles. Ensure the rim of each jar is clean inside and out (use a hot clean cloth to wipe the jars if necessary) and put the lids on. Tighten jars, and while still hand-hot, but without moving the jars, wipe jars with a clean damp cloth and polish with a clean tea towel (it is much easier to remove sticky jam from the outside white the jam is still hottish).

101 Jam making

1 Select jars, wash, rinse, and transfer to oven. Wash and dry jar tops.

2 Measure sugar and transfer to a large shallow tin like a Swiss roll tin (jelly roll pan).

3 Weigh fruit, rinse, shake dry. Put water in pan. Cut fruit, removing stones and transfer to pan. If using stones for added pectin, bundle up in muslin and tie with string. Add to pan.

4 Set up bench with newspaper covered with clean cloth or paper towels. Have somewhere to put the bubbling pan of jam – a cork mat, double thickness of tea towel or newspaper etc. Have ready a Pyrex jug for pouring jam into jars (I find a 500ml (1 pint) jug is ideal for small jars, but a 1-litre (2 pint) jug is better for larger jars). You’ll also need clean cloths for wiping, a long-handled wooden spoon for stirring the jam, and a thermometer warming in a jug of hot water if you have one.

5 Put sugar in oven to warm.

6 Put pan over a gentle heat and let the fruit soften and open up for 7-10 minutes. Bring to a bubble, then boil gently for 10-30 minutes, according to recipe.

8 Lower heat under pan, add warmed sugar, stir until completely dissolved, then turn up the heat and bring jam to a boil. Shake thermometer free of water and add to the pan (most have a clip or a hook so that you can secure them to the side of the pan; mine doesn’t but I hook it on the end of the handle). Cook until setting point is reached (104°C / 220°F). Return thermometer to jug of warm water.

9 Remove jam pan to bundle of tea towels or newspaper. Skim off any frothy scum, or stir it through. Insert funnel into first jar, scoop up jam in jug and pour into jar. Repeat. Fill them all up, then put on the lids.

10 Let jam settle, but while jars are still warm, without moving the jars, wipe outside of jars with a clean damp cloth to remove any stickiness – it’s far easier to do it while the jam is still hottish! Buff with a clean dry cloth. Let jam cool completely, label and store.

Ideas for using jam 

Photography Aaron McLean http://www.aaronmclean.com