I can can...

18 March, 2014

I finally got the right opportunity to open my Christmas present from last year.

This may seem a little delayed. But until now it just hasn't been the right time. But when I headed out into the garden, and came back inside with more tomatoes and zucchini than I could possibly use, I just knew the time had come.


The zukes have been cropping well for some time now, but I've been managing to keep up with the supply. Tomatoes are just starting to hit their strides, and I finally have enough to start thinking about preserving.

At the top are the few proper preserving tomatoes 'San Marzano' and the bottom is a mix of 'Siberian', 'New Yorker' and 'Mr Ugly'.

Now I an a massive fan of the water bath preserving method. I use it when bottling my passata (Italian style tomato sauce) and preserving the peaches but I know that for bottling low acid veg it just don't cut it.

Acid (along with salt and sugar) helps to inhibit the growth of food spoiling and food poisoning causing bacteria. I recall that at around pH 3.5 and below things are safe to bottle with the water bath method. Hence adding vinegar and pickling veg like cucumbers works, as does sugar in jam making, or both vinegar and sugar in chutneys. But I don't want pickled zucchini. I want plain zucchini I can use for zucchini soup in winter when my plants are but a distant memory.

Hence the pressure canner. Pressure canners work by achieving higher temperatures, which kills off bacteria like the delightful botulism causing bacteria which survive standard water bath temperatures. Therefore you don't need the standard acidic/sugary/salty solution, just your veg and water.

I'm doing the tomatoes with this method, as my understanding is that while tomatoes do contain acid, they vary between pH 3-4 and may be safe to water bath, or may not. Better to be safe than sorry, i.e. dead from botulism.

So on that fun note, on with the process.

I washed my produce, and prepared my canning bottles (wide mouth ball mason jars) by rinsing and holding in just boiled water.

The tomatoes got skinned by being put into a pan of boiling water for about 30 seconds, then removed and cooled in a bowl until they could be handled and the skin pulled off.

The whole or roughly chopped (depending on size) tomatoes went straight into the hot jars.

As they filled the tomatoes got squished down until the tomato-y, juicy mixture was around one inch from the top of the jar.

Then it was lids on and into the hot jar holding bay they went to stay warm until everything was ready for the pressure canner.

I then chopped the zucchini into thin-ish, inch-ish size pieces.

These also got about 30 seconds in the boiling water to soften, so they could be well packed into the jars.

These were also squished down, then the veg boiling water remains were poured over also to an inch from the top. Bubbles were removed but running a knife around the edges.

When all was ready, into the pressure canner it went.

Due preserving process was then followed (heat until steam comes out, let steam come out for 10 minutes, then put stopper on and watch pressure build, when pressure at 11 kPa start timer).

The tomatoes and zucchini had to be cooked at 11 kPa for 25 minutes. If the pressure drops below this at any time, the pressure needs to be increased and then the time started again to be sure of safe preserving. So I sat and watched the clock for the full 25 minutes to be sure all was well.

Actually, I had to reduce the heat to its lowest setting, and take it slightly of the burner to stop the pressure going too high. I was surprised such low heat was required to maintain the pressure once it had built up.

When the 25 minutes was over it came off the heat and was set aside to cool and the pressure to reduce enough to open the unit. This took quite a while, about an hour, so I wouldn't want to have a long production line waiting to go in. But when they came out it was amazing as the contents were bubbling away in the jar.

I really wish action photographs were possible.

Now I have zucchini and tomatoes that will safely keep for many a month, without energy input or deterioration.

It almost makes me wish it was winter now.

Almost, but not quite.

What preserving are you doing?


  1. How exciting - do you have to keep them in the dark to keep the colour vibrant?

    1. I know. I already have plans for further pressure canning. I believe (having no experience of this) that it is best to keep them in a dark place, but I have water bath canned tomatoes (before I read about the dubious safety, so threw them out) and they sat on a shelf in the light for 12 months and were still bright and red. So maybe it differs by veg type...

  2. This is great, well done! I really would love to preserve things (not that I'm producing enough to do so at the moment, but hopefully in future I will) but I don't know enough about it. I'd love to do a course or something. I'd be worried about poisoning myself/someone else if I wasn't totally sure how to do it! You definitely seem to know how it works :) Thanks for the post!

    1. Cheers! I too didn't have enough to preserve in the early years, but it builds up quickly :)
      I mostly read books, and started with the fowler vacola unit and just followed the recipes in their booklet. Worked a treat. I'd say just get in there and have a go!

  3. beautiful! the zukes in particular are gorgeous. i hope you have many a successful winter cook up with your preserved summer veg.
    i'm actually going to post about my summer sauce making soon - seems preserving in some shape of form is in the air!

  4. Cheers! I hope so too. Well done on your sauce making, I look forward to hearing all about it!