Canned tomatoes: How to make a store cupboard essential at home

Canned tomatoes are a very present cupboard resident in our kitchen. They are adaptable and reliable, and in oh so many recipes. But this reliance on canned tomatoes is a wee bit troubling.

Firstly, canned tomatoes which were grown in Australia and are not the output of “Big Ag” are difficult to find. In fact, I have had all of zero successes in sourcing Australian grown, organic-ish canned tomatoes (if you know of somewhere, please let me know!). When our climate (in the state we understand it to be in – perhaps not in the uncertain future so much) is so well suited to growing tomatoes, surely there is no legitimate reason for imported tomatoes.


Secondly, every time I decide to consume a can of tomatoes I produce one can going to waste. This I don’t like. Though it’s not plastic – which means it’s not quite at the top of the ‘bad guys’ list, it’s still waste which perhaps could be avoided. I’m also keen to learn the skills which in the past have been fairly central to homemade food, though increasingly are now within the realm of factory processing.


So with lovely, flavourful, juicy tomatoes in season from some of our local growers at the moment, it seemed like a good opportunity to make my own canned tomatoes. Though, starting small this time with a fairly manageable batch of tomatoes because I’m learning and, well… botulism (there’s some words on this in the P.S.). Using the canned tomatoes recipe from Marisa McClellan’s Food In Jars, here’s the process we followed.

Food in Jars

Wash the toms, remove the cores and score the bottom of the tomatoes with an X.

Tom with X

Dunk the toms into a pot of boiling water, in batches as they would fit, for about 3 minutes, then pop them straight into chilly water. Peel the skins off, using the scored marks to help. The skin should peel right off (I used the back of a paring knife to scrape off any pulp that stayed with the skin when I peeled them so that it was really just the skins being discarded).


Roughly chop the tomatoes, and place into a sauce pan. Bring to a boil then simmer for around 40 minutes to thicken the sauce and deepen the flavour.


Meanwhile, prepare the stockpot for processing, and get some jars sterilising by boiling them in the pot. I don’t have a rack for the base of my stock pot, so to elevate the jars off the bottom (to help with the heat circulating fully), I stick in a tea towel. (This is okay, and works, but is a real bother and EVERY TIME leads to boiling water splashing on to my arms and face.) Get the lids sterilised by simmering in a small saucepan, too.


When the tomato mix is good and done, take the jars out of the stock pot and let the hot water evaporate out.

Jars ready


Add the acidity-giving-ingredient (in my case, granulated citric acid) to each jar and fill with the tomatoes.

Citric acid

I expected to fill three 500ml jars from my 1.7kg of tomatoes, though ended up with just two 500ml jars and about 100ml left over. So I just went with the two 500ml jars for processing (the excess was stored in the fridge overnight then added to a black bean and tomato chili soup).

Canned toms

Place the lids and rims on the jars, make sure they’re secured and then lower in to the boiling water bath. Process for 35 minutes, then remove and allow to sit overnight before removing the rims. Check that there is a good seal (the lid is suctioned onto the jar) and they’re done!

So I ended up with two jars of tomatoes. The cost of the tomatoes – from a local, small-scale, low-chemical farmer – means that these were pretty expensive canned tomatoes. The time taken wasn’t insignificant, either. All up it took a few hours plus cleaning. But if I managed to work with, say, 10.7kg rather than 1.7kg and processed in batches, perhaps it would be a bit more economical. Regardless, it was fun and interesting and surely that’s more important (if you have the luxury) than saving a couple of bucks on canned tomatoes.

A couple of thoughts about the impact of these tomatoes. The fruit themselves, I am satisfied with as being responsible food. Though often we assume doing things at home is automatically better than factory made, I wonder about the energy consumption of these two jars of tomatoes. I had the stove on for quite some time – cooking the tomatoes, sterilising the jars, sterilising the lids and rims, and processing the tomatoes. I also used a number of litres of water just for heating and nothing more.

How would this compare to the efficiencies in water and energy if mass-produced? With confidence, I feel I can say that per unit these would be very water and power hungry jars of tomatoes. But how does this counter stepping outside of a food system besieged with chronic failings, and where corner-cutting, low quality, and opaque practices are symptoms of the fact that the food system designed for profit, often at the ‘expense’ of people and the state of the environment? How do the power and water uses compare to mass transit, mass-scale cleaning, harvesting, storage, spoilage and wastage, and so on?

I do think it’s arrogant and naive to think that the actions of one (i.e. myself) can have a net positive impact on a system that is really quite broken. So maybe this has been little more than a feel-good exercise which really carries more burdens than merits. I don’t know, but in any case it brings learning. If you have any thoughts on this, I’d be most pleased if you would share!

Thanks for reading, and just for interest’s sake, the two jars of canned tomatoes were used in a chili tomato white bean soup (from the River Cottage Veg cookbook) and a spiced split red lentils dish (from Yotam Ottolenghi’s Plenty).


Post script: A note on acidity, temperature, and botulism

Surprisingly, the acid content of tomatoes is low compared to other fruits. This means that unless a very high temperature is reached during canning (higher than my stock pot will take us), then the conditions are ripe for the growth of the bacterium which causes botulism. Not nice! The way to counter this is by increasing the acidity of what is being canned.

So basically, botulism becomes a risk when you are home canning (without a pressure canner – i.e. using a stock pot as I do) foods with low acid content. The point is – I’m not yet confident navigating around safety and acidity, so keeping it small to begin with. I added in granulated citric acid to up the acidity of the tomatoes. I’m not sure how I feel about citric acid yet, and this was my first time using it (as you would expect, the jars of canned tomatoes were pretty acidic). To my knowledge, it’s created in a lab in order to ensure consistent acidity.

I like the romantic agrarian idea of squeezing in a few lemons, but it’s just not accurate enough to guarantee no-botulism. Something I would like to look into more is using lemons, then pH testing the mix. I don’t know how reliable this is, though, and I’m not yet confident to trust it! The pH testing is very simple, but what if the acidity level varies throughout the mix? Randomised sampling throughout the saucepan? At what point should I test it? For now, citric acid it is (another option is bottled lemon juice, which ought to have a consistent acidity level. I went with citric acid as the packaging seemed to be less, though a nice glass bottle of lemon juice could do the job next time).