Ask Corby: An Introduction to Marmalade

Our expert recommends the best brands, tells how to keep them fresh, and explains why they're essential to everyday life

Q. Elizabeth Field, a food writer in Providence, writes: I'm writing a small book on marmalade and am in the midst of testing loads of recipes. When I seal the marmalade in a jar and put it away, then take it out to taste a few months later, must I then refrigerate the jar? I know this sounds like an elementary question, but I'd really love NOT to have to refrigerate the opened jars.... they take up a lot of space.

A. Thanks! And ... I'm afraid you do have to refrigerate the jar. As you know from your own experiments, acidic fruits with high acid and low pHs retard mold and, if you add enough sugar and pectin to achieve a firm set and seal the jars well, will keep for years. Readers though not friends will be surprised if not shocked to hear that I still have, and use, marmalades I made from the spree I went on more than a decade ago, making all sorts of citrus marmalades. The definitive reference book Putting Food By, by Janet Greene, Ruth Hertzberg, and Beatrice Vaughan, says why jellies are generally safe:

Without perhaps realizing it, jellymakers rely upon the ability of sugar to tie up the water [that micro-organisms need to grow] by chemical means. This ability, plus the increased acid of the fruit, the added heat in cooking, and the lack of oxygen in the jelly jar, all add up to a virtually unbeatable combination for a safe and attractive product.

All great, but marmalade, which the authors define as "a tender jelly with small pieces of citrus fruit distributed evenly throughout," is subject to the mold-producing oxygen as soon as the seal is broken. Mold can form fairly quickly at room temperature, and though my own instinct has always been simply to skim it off with a spoon, both the authors of Putting Food By and Pam Corbin, in the recent River Cottage Preserves Handbook, recommend avoiding this, as Corbin writes in a section she calls "The Four Spoilers":

A bit of mold on the top of an open jar of jam should not be scooped off and ignored; as they grow, some molds produce mycotoxins that can be harmful if eaten.

This goes for bread, too, as I've field-tested to my regret when I've simply cut away spots of mold.

The jams and marmalades I make are actually more susceptible to mold than what the pros do, because I always look to reduce the sugar content, which makes for waterier jams, though I do keep boiling until I get something like a decent set. Thus I put anything I've made straight into the fridge as soon as I open it and, of course, eat several spoonfuls (no, I haven't suffered ill effects yet from my aged marmalades, but for liability reasons I'd best not recommend eating bottles quite as old as the ones in my cellar). And as to what I've made lately, I've taken to Zeke Emanuel's extremely easy raspberry jam, which is just crushed raspberries boiled with sugar. It's quite liquidy and requires refrigeration from the moment it's done.

I did buy a pound of Seville oranges when they showed up at my local Bread & Circus, sorry Whole Foods (which bought the local chain by that name), at the end of January, but didn't make the marmalade I was sure I would. And I confess to relying on the superb products from Katz and Co., which I make sure to order at the end of August, since their apricot and raspberry sell out fast for very good reason. I've got a jar of raspberry preserves on the kitchen counter now, three-quarters empty without a hint of mold, because of the solidity owing to sugar and professionalism. But I should add it's still cool out, and we've only had it open a week or even less (you'll see why if you order some).

I would be less nonchalant about apricot, a fruit with a higher pH, meaning lower level of acidity, particularly if this summer I make again the recipe inspired by the marvelous June Taylor, who sells at the Ferry Plaza Market and various California shops as well as online. When I wrote about her apricot jam and other preserves, she gave me a recipe I used with great success. This winter I'll apply for help duplicating her too-good candied citrus peel—the way I most want to use those unexpected Seville oranges.

And good luck with your own work!

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Image: L. Marie/flickr

By the way, I've very much enjoyed your writing on marmalade. Have you made any interesting ones lately?