The Accidental Scientist: Science of Cooking Exploratorium.edu
Candy Bread Eggs Pickles Meat Seasoning
Ask the Inquisitive Cooks    

"Any suggestions for making jam from mulberries?"

Hello Chaps,

I'm heartbroken due to boiling up some 5 pounds of beautiful mulberries to make jam, only to have them not set on me. I subsequently added the juice of a lemon and reboiled, but after a total of two hours or so of boiling, I've made mulberry toffee.

My wife believes that my fundamental error was to use brown (demerara) sugar. I can't find anything in the literature which explicitly excludes its use, but I've always made successful jams with white sugar, and had a similar experience when we ran out of white sugar and I tried to make raspberry jam with demerara last year (though that half-worked...).

Can you help? There's nothing worse than wasting that amount of lovely fruit.

Kind regards,
Richard Davison
Bristol, U.K.

 

Still have more questions? You'll find more answers in our archived monthly feature articles by the Inquisitive Cooks.

(Meet the Inquisitive Cooks)

     
Dear Richard,

We've tossed your question around a lot, for it's hard when preserves don't work! We also admire you for working with mulberries, as there's not a great deal of information about preserving them. While we hate to disagree with your wife, we don't think it's the demerara sugar that caused the problem.
More likely, your predicament has to do with the proportions of pectin, sugar, and acid. As you probably know, these proportions vary depending upon the type of fruit you're using. Mulberries are among those fruits that are not high in pectin. You were wise to increase the acidity by adding lemon juice. Nonetheless, if there wasn't sufficient pectin, the mulberries couldn't set.

Another factor in setting rests on the maturity of fruit. When fruit is overripe, pectin changes to pectic acid, a form of pectin that does not promote jelling. Mulberries are not usually picked from the tree but allowed to fall to the ground when they're ripe. By the time they're gathered from beneath the tree, much of the pectin content has likely already changed to pectic acid. So the gelling capacity is further reduced by the fruits' maturity.

Mulberries are ancient fruits of Asian origin, reportedly cultivated in China 5,000 years ago. They were, of course, more in demand for their leaves, which were the primary food source for silkworms. Their fruit is still not well known, so recipes are not easy to find. The recipes we have located use added commercial pectin to guarantee that jams and jellies set.

The unusable product that you ended up with is probably the result of overcooking. Longer cooking actually breaks down the pectin molecules. Eventually the evaporation of water makes jam thick but results in a gummy, sticky product, often with a darker color caused by the sugar caramelizing during the extended cooking time. Jam is best cooked rapidly, in small batches.

Thanks for being inquisitive! We've learned more about mulberries, and likely your question has also made others more aware of some new angles on preserving.

Anne & Sue
  
 

 

- - - Science of Cooking - - - Webcasts - - - Ask The Inquisitive Cooks - - - Share & Discuss - - -

 

© Exploratorium | Use Policy | Privacy Policy