Sales of jam have gone up 20% in the past year, the rise thought to be partly due to more baking during lockdown (something has to go on that sourdough bread) and, with many people working from home, more time to make breakfast rather than grabbing something en route to the office. But why buy jam when you can make your own? Unlike banana bread, the jars of jam you make now should last a few months or more – maybe even outliving the pandemic, when one day you’ll reach into the depths of a cupboard and retrieve a dusty jar with a label reading “February 2021”. Now there’s a happy thought. Be realistic While the idea of filling an old-fashioned larder with rows and rows of jars might appeal to your new survivalist mindset, it’s not necessary. Apart from anything, it’s the wrong time of year – you’re not dealing with a glut of homegrown fruit to preserve. “Why not just make one or two jars of something really delicious that you like?” says Thane Prince, food writer and author of Perfect Preserves. Pick a pan “You’ve got it all in your kitchen,” says Prince. “You need your biggest pan. You probably shouldn’t use aluminium pans because aluminium and acid react.” Lillie O’Brien, founder of the preserves shop London Borough of Jam and author of Five Seasons of Jam, recommends a heavy-based pan. “If you do it with a thin base, the jam catches [and burns on the bottom] really quickly.” Both like cast iron casserole dishes. O’Brien favours a low, wide pan “so the liquid evaporates quicker”, but Prince recommends higher sides because “when you boil it, it rushes up the sides”. Don’t buy lots of other equipment You can buy a jam thermometer, but neither Prince nor O’Brien ever use them. “I think they give you a false sense of security and often they are not calibrated finely enough, and you’ll find the jam is burned,” says Prince. O’Brien recommends a microplane zester, a funnel with a wide hole so the fruit can pass through and a decent spatula (that won’t melt in boiling jam) for easier jam-making. “Looking at someone pouring jam out of a pan and then leaving all the bits makes me go aargh.” You do need sterilised jars – wash in soapy water, then put them right side up in a 110 degree oven for 30 minutes. Prince says you can also use the hot wash on a dishwasher. Boil lids and rubber seals in a pan for five minutes. Prince doesn’t bother with waxed paper discs placed on top of the jam (used to prevent condensation, and mould). “I don’t really think it’s necessary with modern jars.” Embrace sugar Yes, we know sugar is the enemy but why do you think jam tastes so good? People are horrified, says Prince, when they realise that most jams have about equal weight sugar to fruit. It’s the sugar that preserves the fruit, and helps the jam set by encouraging the release (along with acid, usually in the form of lemon juice) of pectin from the fruit, the gelling agent. You can find “sugar-free” recipes in various healthful areas of the internet, but these are basically fruit purees, not jam. You could use much less sugar, but this will create “the runny jams you get on the continent,” says Prince. “They won’t set and you need to keep them in the fridge.” O’Brien uses less sugar than is traditional for set jam – between about half and three-quarters of the weight of the fruit, and uses sugar which is less refined, such as demerara, in some recipes. “I prefer the taste because it’s richer, but it’s double the price of caster sugar.” While lots of jam-makers add pectin, usually in the form of jam sugar, O’Brien doesn’t; she says a bag of supermarket caster sugar is fine. “If you have the right balance of fruit, sugar and acid, it will set.” But jam made from low-pectin fruit, such as strawberries, won’t be as thick, she adds. Don’t cook too much Or too little, says O’Brien. Between 1kg and 2kg of fruit is about right, she says, and will produce four or five jars. Make more than this and it will take too long, stew “and lose its life”. You want to cook it quickly but not excessively so – with lower quantities, it will cook too speedily and can burn. Choose the best fruit Jam isn’t an opportunity to use up withering fruit. If you wouldn’t eat it fresh, don’t preserve it, says Prince. Misshapen is fine, mouldy is not. Go seasonal It’s cheaper, tastier and more exciting. “It’s lovely to capture a moment in time when you’re making jam, as if to preserve a story by stirring it into the pot,” writes O’Brien in her book. Right now, Seville oranges are in season so you should start with marmalade. O’Brien has an excellent, low-effort recipe that involves boiling the whole fruit for around 35 minutes, leaving overnight, then boiling some of the cooking liquid with the juiced oranges, peel, sugar and lemon juice. “The hardest thing with marmalade is getting it to set,” she says, so don’t worry if you have a disappointing first try. “It’s one of those things you have to do over and over again to get a feeling for it.” Yorkshire forced rhubarb is also available now. “It’s so beautiful, sometimes I don’t put anything else in with it,” says O’Brien, though she does have a recipe for forced rhubarb and grappa. Summer is peak jam-making time, but if that seems too far away, look out for produce making an appearance soon. O’Brien loves French Gariguette strawberries, “which are really beautiful but quite expensive. You get green gooseberries towards the later end of spring.” Field-grown rhubarb will start to be harvested too. Prince says you can use apples and “if you’ve got some blackberries in your freezer, you could make blackberry and apple jam”. In terms of what you can find fresh at the supermarket, you can make jam with pineapple and bananas, which are always available. Chill out “You might have fruit stashed from last summer in your freezer,” says O’Brien. “If the fruit is good to begin with, and frozen, it’s fine.” Prince says a bag of frozen berries from the supermarket is perfectly acceptable. Neither would recommend tinned fruit as it’s too watery. Get set The basic rule is to boil jam at 105C for it to set, which is where a thermometer can be handy, but not foolproof. “Every fruit is different,” says O’Brien. “Lemon marmalade will set quickly – I could get it to probably 90C. Whereas strawberry jam is going to take a lot longer to get it to set. It might get to 105C, but need to cook for five more minutes.” Both O’Brien and Prince say the “freezer test” to see if jam is ready works best. Put a plate or saucer in the freezer to chill, then dollop a bit of jam on it. O’Brien looks for it to form a skin; Prince says to push it with your finger. “If it wrinkles, you’re good to go.” Venture beyond strawberry O’Brien has numerous creative combinations: roasted peach and fennel, plum and tomato leaf, raspberry and liquorice, fig and Earl Grey tea leaves. She includes what she calls “friends of jam – leaves, teas, spices, wines, spirits, flowers and herbs”. Prince also enjoys inventive combinations. “If you make blood orange and Campari marmalade, you can almost pretend it’s like having a Negroni for breakfast.”