Why some marmalade doesn’t go mouldy: sugar, lids and clean jars

A reader in Berkhamsted asked why her son’s marmalade never goes mouldy even though he doesn’t warm the jars or use paper and cellophane, he simply puts the lids on. Camilla Wynne, preserver and author of All That Crumbs Allow, said the high sugar content is most likely the reason: “The chance of mould developing is low because there’s so much sugar to balance the bitterness of the orange peel.” She added that “mould needs water to do its thing, and sugar binds to water,” and recalled a student who developed mould after she had been “reducing the sugar in her recipe over the years.” On the lids, Pam Corbin, author of Pam the Jam: The Book of Preserves, said: “He’s more right than she is.

Nowadays, we have fantastic food-grade lids, which have a wax seal inside and keep preserves safer than a wax disc and cellophane would.” Corbin warns against wax discs on paper because “as the marmalade cools, condensation forms on top of the paper, so you’re more likely to get mould.” Wynne said what’s “most important” is to use only clean new lids: “This will help them seal properly.” Corbin advised that if you do reuse lids, check there aren’t “any dents or odours” and, if acceptable, “pop them in a pan of water and simmer for five minutes to make sure they’re clean.” Experts differ on jars.

Key Topics

Culture, Marmalade, Berkhamsted, Camilla Wynne, Pam Corbin, Food-grade Lids