OK, so really this is just a recipe. Or rather, a series of warnings about how not to cook nuts and fruits. But science does come into it.
Specifically, Mr Boyle’s bits of science linking pressure, temperature and volume.
The problem is that, like popcorn kernels before they go all big and fluffy, apples and sweet chestnuts are basically sealed containers full of water.
If you heat up the sealed container, the pressure in it goes up. Unless its volume can go up.
It’s been a good year for apples and there are still lots on and around the trees in hedgerows or gardens or the community orchards. We were also lucky enough to be given a bag of foraged sweet chestnuts (not to be confused with horse chestnuts- check the difference here if unsure)- lovely big plump ones instead of the skinny empty shells which are usually all we manage to find.
With the apples, we cut out a square of core, cut a deep ring around the waistline of the apple then stuff the hole with raisins, brown sugar and cinnamon. Or bought mincemeat, which is broadly the same thing but even nicer.
In theory, baking the apples in the oven should be really easy, resulting in gorgeously fluffy or creamy (depending on the variety) steamy sweet apples. In practice, I have learned that it’s safest to bake the apples inside a big, lidded dish. This way, when the apples inevitably explode (not everybody manages to explode apples reliably- it is a speciality of mine) at least they are contained and remain edible.
Failure to put the apples in a lidded dish results in an oven completely coated in welded-on burnt apple jam, followed by a lot of scrubbing the oven. Every. Single. Time.
In theory, cooking at a lower temperature or for a shorter time should prevent the explosions. I don’t seem to be able to get the hang of making the apples both cooked and unexploded. Thanks a lot, Mr Boyle.
What happened to the chestnuts should have been entirely predictable. Not to mention avoidable
They have a much harder outer layer than apples do.
I did not score the outer layer before putting them in a hot oven to roast, having missed that bit on the instructions.
To be fair, the pinging noises of chestnut shell ricocheting off the oven interior were quite entertaining. And we did remove the tray after only half had exploded.
Interestingly, there was almost no chestnut remaining on the inside of the exploded shell pieces. In order not to feel too disappointed about the loss of all that chestnut (and subsequent oven cleaning- though nothing like the exploded apple), I am counting this as an interesting experimental result- albeit one I recommend that nobody repeats.
And I will not be roasting chestnuts on an open fire unless they are safely contained in something with a nice, sturdy lid.