Tips for making jams with Stone fruits
Fruits like Apricots, Peaches, and Nectarines have a stone inside. These fruits are referred to as “Stone Fruits”. Recipes for Apricot and Peach Jams usually talk about using the kernels inside the stone as part of the jam-making process. The kernels provide additional pectin for setting and a mild touch of flavour to enhance the overall finished jam. I have included my tips for managing the kernels, how many to use and some precautions. I hope they are useful for your next session of stone fruit jam making. Please use them and share them.
Stone Fruit Pits and Kernels in the Making of Jam
Pectin and Flavour: Stone Fruit pits (stones) and kernels contain pectin. Pectin helps jam thicken during the cooking process. The flesh and skin of stone fruits are much richer sources of pectin than the pits and kernels. Some fruits have higher levels of pectin, like Apricots, while the ripeness of the fruit will also increase the levels of pectin. Cooking the kernels with the fruit may help extract additional pectin and flavour that may otherwise be left behind.
Stone and Kernel Tips
How to separate the fruit flesh from the stone?
I generally cut the fruit in half with a knife and twist the two halves, this usually releases the stone from the flesh. For some stone fruits, like nectarines or depending on the ripeness of the fruit, the stone is more attached. In these cases I might need to cut the fruit into quarters and lever the stone out
How do you get the kernel out of the stone?
My method is not fancy, but it works, more or less. I have been using a hammer to smash the stones on a concrete slab/paver to remove the kernels. Annoyingly when the stones have just been removed from the apricot or peach, the stones are slippery little buggers, and generally they end up shooting off and I end up chasing them all over the place.
Between two Tea Towels: Placing the stones between 2 tea towels on a concrete surface and hitting them with a hammer works for some people
Freezing the Stones: An accidental discovery….Once, after I had smashed up the stones of 2 kg of fruit, I had enough kernels for 4kg of jam. Rather than waste the kernels, I decided to freeze the stones from the other 2kg of fruit. The next time I was making apricot jam I forgot to organise the kernels until the last minute, so I grabbed the bag of frozen stones and took them out to smash them without thawing them out. It was so much easier with any residual fruit flesh frozen. No more stones slipping on the concrete. I then tried the same with peach stones, and it worked for them too.
How hard do you hit the Stone with a Hammer?
This takes a little practice. When the stone shatters, it can ricochet a little bit. Don’t hit them too hard or the kernel will also shatter. Good luck.
How many kernels do you add to the Fruit for cooking?
If I have 4 kg of fruit, I generally use the kernels from approximately 2 kg of fruit.
How do you add the Kernels to the Fruit for cooking?
I make or buy small muslin bags, place them in the fruit mixture. I take the bag out when the jam is ready to put into the sterilized jars.
Can you leave the cooked kernels in the jam?
Using a muslin bag of kernels makes them easier to retrieve. Leaving them in the mixture makes the jam look less attractive to some jam lovers.
Is it safe to use apricot kernels in the making of jam?
Be cautious: Apricot and other Stone fruits contain amygdalin, which can release small amounts of cyanide, a toxin. The cooking process reduces the toxicity. Eating raw kernels is not recommended, especially for children who may mistake them for almonds. More info about kernel food safety
Using the whole fruit is an integral part of old-fashioned jam making. Cracking open stone fruit pits to remove the kernels for their pectin and flavour can take a little perserverance and practice. Freezing the pits appears to assist the smashing process.
More questions about jam making?
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