Posted on by Martin

HOWTO: Keep the mould from your marmalade

(I owe Kenny Harris big for this one.)

I love marmalade, but I love it in phases: I’ll go for months without being the right mood for it, and then BAM I’ll have a late-evening craving for a slice of toast, dripping in butter and smothered in Chivers Olde English. Until last year, I’d go to the cupboard, grab the aged jar from behind the little-used condiments, only to have my desires thwarted by layers of semi-sentient fungus.

Fortunately, there is a very simple way of making your marmalade last longer: don’t let it come into contact with any oily substance, i.e. butter (or margarine). I have no idea why this works; I’m just delighted it does. Use a separate knife or spoon to extract your marmalade instead of the one you buttered your toast with, and your marmalade will stay mould-free for months.

I don’t know if this works the same for jam. Jam doesn’t last long enough in our household to provide an adequate experimental baseline.

4 Replies to “HOWTO: Keep the mould from your marmalade”

  2. My guess: I think the oil in butter/margarine provides food that’s palatable for micro-organisms, and provides a base for them to grow. Once that happens, mould can form (since spores are absolutely ever-present), and it builds up as old mould dies and provides more substrate. Things like honey and marmalade (at least the marmalade that I make) contains so much sugar that it’s more or less unpalatable.

  3. Could it be anything to do with the fact that the marmalade is fairly sterile, and using a clean knife doesn’t introduce any (many) foreign bodies into it, but a knife wiped with butter/toast/etc does, thereby causing growth?

    Just wondering….

  4. No. There are spores absolutely everywhere, so opening a jar of marmalade will let them in. I think this is explained by osmosis. The marmalade is hydrophilic, ie, it sucks in moisture. Spores come into contact with the marmalade, and you end up with a mucous membrane with hydrophilic marmalade on one side, and moist cell contents on the other. Water moves across the membrane, and the spores die.

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