He never warms the jars, so why doesn’t my son’s marmalade go mouldy?

3 hours ago 2

When my son makes marmalade, he never warms the jars or uses circles of baking paper and cellophane – he just puts the lids on. It never goes mouldy, so am I wasting my time doing it the “proper” way?
Dagna, Berkhamsted, Herts
You can’t get much sweeter than marmalade, and this is most likely the reason for both Dagna and her son’s success, despite their differing strategies. “The chance of mould developing is low because there’s so much sugar to balance the bitterness of the orange peel,” says Camilla Wynne, preserver and author of All That Crumbs Allow. “Mould needs water to do its thing, and sugar binds to water.” She recalls a former student who, like Dagna’s son, simply ladled her marmalade into jars and closed the lids. All was fine until one day the student’s latest batch of marmalade was covered in mould: “She’d been reducing the sugar in her recipe over the years, so her method no longer worked because there was available water for mould to grow.”

But back to the particulars of the family dispute. “He’s more right than she is,” says Pam Corbin, author of Pam the Jam: The Book of Preserves. “Nowadays, we have fantastic food-grade lids, which have a wax seal inside and keep preserves safer than a wax disc and cellophane would.” Some people put a wax disc under the twist-on lid, too, but for Corbin that’s a hard no: “As the marmalade cools, condensation forms on top of the paper, so you’re more likely to get mould.”

What’s “most important”, however, is to use only clean new lids, Wynne says: “This will help them seal properly, and if your marmalade is sealed, you won’t be worrying about anything untoward happening.” Depending on how many jars you’re making, this can be an expensive strategy: “If you want to reuse your lids – and I do – make sure there aren’t any dents or odours,” Corbin says. “If they’re damaged or smelly, throw them out. Otherwise, pop them in a pan of water and simmer for five minutes to make sure they’re clean.”

On to the jars, which is where opinions divide. “You definitely want to heat them, because that’ll make sure there’s no mould or yeast that could potentially cause problems,” Wynne says. Corbin, meanwhile, doesn’t think this is strictly necessary – so long as the jars are sparkling clean, that is. “I would warm jars only if I was making a reduced sugar preserve, because you won’t have that high temperature,” she says (the sugar is what allows marmalade to reach a high temperature). “I’m also mindful that people have done things the same way for generations, so if it makes them happy, let them do it.”

What is unforgivable, though, is overcooking your marmalade, Corbin says: “It’s the biggest crime of marmalade making. When I’ve been a judge, a lot of marmalade tastes like barley sugar, because it has become too caramelised.” So how do you know it’s good to go? “When all the light, white bubbles have disappeared and it begins to look glossy on top. There will also be a slower, more relaxed rhythm to the boiling.” Finally, always fill those jars practically to the brim: “I see people on Instagram filling them only halfway, but any air in the jar can bring contaminators,” Corbin warns. Spread the word.