3 Lower Carbon Energy Efficient Ways To Cook Fruit


Days 29, 30, 31 & 32 of 365 Days Of Low Carbon Living.

Summer in my garden means lots of fruit. And with so many plums at the moment, both on my trees and on the ground, the question arises: how to use them all so none go to waste? This is especially important given they now contain nutrients and water they have extracted from my soil and their come with zero food miles and thus, unlike anything I buy, zero damage to our climate from energy used to grow, transport and store them.

Preserving them means that they can be eaten later.

One of the quickest and easiest ways of preserving fruit like plums is cooking and freezing.

How low in carbon this method is depends on the source of heat for cooking and the origin of the electricity to run the freezer. Does it require burning of anything, and thus add more damage to our climate?

Also, freezers use refrigerants, and the gases currently as refrigerants are by far the most damaging to our climate (although they are being phased out).

Over the last four days of January I cooked plums in three different, increasingly low carbon ways.  (Why it took 4 days will become apparent.) Then it was simply a matter of freezing them (in re-usable containers, of course).

Method 1: slow oven cooking

I took advantage of a cool and cloudy day to do some oven cooking.

Naturally, I wanted to make the most of the energy and greenhouse gases* used to heat the oven – so I cooked as many things as possible at the same time. (*My stove is still gas.)

In the bottom (coolest) part of the oven I put an uncovered casserole of pieces of windfallen plums.

The result: delightfully rich and sticky. The cooked fruit was still somewhat tart (because most of it was not fully ripe to begin with) but it was a real treat served with with coconut yogurt and a sprinkle of coconut sugar for sweetening. Even better: stirring it all together.  Yum!

The batch shown in the picture was the second batch I cooked this year in the oven.  It spent most of the time in the middle of the oven where, even at ‘low’ temperature, it cooked more quickly and so ended up more moist and nearly burnt on top. Still delicious, though – just not as good as the first batch that was cooked at a lower temperature.

Method 2: slow microwave cooking

More cloud and more windfallen plums to use.

This time I used even less energy for cooking. As my electricity at this time of year is all sun-powered, I am not contributing damage to the climate…but the Canberra still does not get all its electricity from clean renewable energy and there are plenty of people and times here (and elsewhere!) where electricity use means climate damage.

Again I used a casserole.  However, this time I covered it with a loose lid with large holes in it (the sort you use to cover food being reheated) to prevent splattering the inside of the microwave.  I hoped the holes in the lid would allow plenty of steam to escape and the cooking would approximate slow oven cooking.

The result: much more moist than cooking in a conventional oven.  Another time, I tried ‘reducing’ the liquid by ‘finishing it’ in the oven – but it is tricky getting the juice to thicken without the fruit burning. However, microwave is good for cooking efficiently in a hurry or at night or on cloudy days.

Method 3: solar cooking

Finally, a sunny day!

Now I could try cooking the plums in the solar cooker a friend and I made (largely from re-purposing corflute signs) quite some time ago.

Using sunlight to cook means no pollution, no damage to the climate and no bills (except for whatever was used to make and/or buy the cooker – but that applies to all methods of cooking except placing fruit direct in natural heat).

Solar cooker with plums in casserole

This time I covered the casserole with its glass lid to help with heating and keeping the heat in the casserole and thus cook the fruit.

I also put the casserole on some terracotta ‘pot feet’ to lift the casserole above the silver bottom of the solar cooker.  I hoped that this would allow sunlight to be reflected onto the bottom of the casserole, thus helping to maximise the amount of sunlight hitting and heating the casserole.

Pot feet in bottom of home-made solar cooker after rain

As it turned out on day 31, I only managed to get half a day of solar cooking.  The plums were tender, but firm rather than the rich stew I was seeking.

So I put the casserole and its contents in the fridge overnight and set it out in the sun again the next morning.

Because I was going to be out most of the day, I tried to angle the solar cooker to where I thought it might get the most sun throughout the day.

Unfortunately, it clouded over and then rained in the afternoon before I got home.

Casserole of plums in home made solar cooker in rain

The result: the fruit was cooked and delicious – somewhere between the results from method 1 and method 2.

Plums cooked in solar cooker

Importantly, the fruit was cooked differently depending on where it was in the casserole:

  • On top, the fruit was drier and darker, with an intense toffee flavour – like sundries sultanas. Why was I surprised – it had been dried in the sun!
  • Underneath, the fruit was soft and retained its colour.  There was also juice, but not as much as the other methods.

My conclusion: each method has advantages and disadvantages, and solar cooking of plums definitely has acceptable results – and no carbon emissions or financial costs.

The challenge

Next time you want to cook fruit, try a lower carbon method – and let me know your experience.

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Till next time…