Canning, bottling and preserving in a steam oven is a great way to make use of your appliance, but it can be daunting if you’re not already experienced at making preserved and bottled foods. I want to change that, and show you how easy the steam oven makes it to preserve food in jars, even if you’ve never done it before.
Minimizing food waste by preserving excess has a huge benefit to the environment and your wallet. And having a stash of pretty jars, full of the season’s bounty to get you through the less-exciting produce months, is so satisfying.
I’ve been playing with preserving different foods in my steam oven for a few years now, and though I’ve still got plenty to learn, I want to share some basics so you can reap the benefits of home preserving too.
I created a pdf chart with a general overview of the temperatures and times I use for preserving in a steam oven; I recommend downloading and printing if you’d like a quick reference guide. I still recommend reading the full article below for more thorough guidelines!
More than with many other types of cooking, preserving requires knowledge of times and temperatures. There’s specific equipment and detailed processes for dealing with your food so it’s hygienic and safe to keep for a long time. But I don’t want that to put you off! With your steam oven and an understanding of the basics (or an ability to follow basic directions), it’s not hard at all. Canning and preserving is also very formulaic, so it’s easy to repeat once you know the process.
What exactly do I mean by canning, bottling and preserving?
Canning, bottling and preserving are all terms for foods that are processed in – you guessed it – cans, bottles and jars, so they keep for a long time at room temperature, ready to open and eat whenever the urge strikes.
For the purposes of this article, the terms canning, bottling and preserving all refer to foods processed in your steam oven, in glass jars or bottles. Read on for more detailed explanations of each term.
Canning, in the strictest sense, is food preserved in cans. But it’s colloquially a reference to food preserved in jars, too. Given the specialist equipment required for preserving in cans, most home cooks these days preserve in glass jars or bottles. They’re easier to get and easier to process.
I refer to bottling as being for fresh fruits and vegetables which you want to remain whole or in sizeable pieces. The food is covered with a sugar syrup or vinegar/brine pickling liquid, then heated to a hot enough temperature and for long enough time to pasteurise. The idea is to retain the food’s texture and colour to enjoy at a later date. In most cases you can bottle from start to finish in your steam oven, as long as you’ve mixed up your syrup or pickling liquid first.
Preserving is more for jams, compotes, sauces and chutneys, where produce is cooked to change its form. Your jams and chutneys will need to be cooked as usual on the stove, but you can then put them into jars while hot and process in the steam oven to create a seal.
Note that for food safety reasons, I do not use my steam oven to preserve low-acid or meat-based products. These need a pressure canner rather that the water bath canners your steam oven will mimic. When it comes to high-acid or high-sugar fruits, vegetables and pickled preparations, though, there’s plenty you can try out as a beginner.
How does water bath canning/preserving work?
Water bath canning at the most basic level needs just a very large pot. You may have seen dedicated water bath canners, though; large and deep pots which commonly come with fitted racks and tongs for stacking jars or bottles into.
In a water bath canner, the jars are submerged under water and heated. This kills certain bacteria and drives air out of the structure of the food, as well as expelling excess air which was trapped in the jar during packing. When the jars cool down, a vacuum seal is formed, creating a hygienic environment which allows you to store the food for a long time.
Preserving in a steam oven instead of a water bath canner
Instead of filling a large and heavy pot with water, then lowering and lifting very hot jars into and out of that pot, preserving in a steam oven means you just pop all the jars onto a tray and slide them in!
Preserving in a steam oven does the same job as the hot water in a water bath canner. Put the jars in, let them heat for the correct amount of time, and you’ll get the same vacuum sealed result as you would in the water bath.
There is one more great benefit to the steam oven over a water bath: temperature control and consistency.
Having more precise temperature control than a boiling pot means you can heat and hold foods at slightly lower temperatures. This retains the best colour, flavor and nutrients, while still making them safe for storage.
Pickled vegetables are a good example of this; I heat my pickles to 185°F/85°C instead of 212°F/100°C, so they stay more crunchy and have far better color than if I boiled the jars. As long as you heat the jars long enough to pasteurize the contents, this lower temperature is safe. Go to my pickled vegetables recipe if you’d like to try them for yourself.
What equipment do you need for preserving in a steam oven?
When it comes to equipment, apart from your steam oven, the only essentials are sturdy glass jars and new (or almost-new) lids with intact rubber seals. Using old lids which have sealed other foods previously means you could introduce unwanted bacteria into your preserves, or the rubber may be degraded and not vacuum seal properly after heating.
My favourite jars for preserving are Ball (US) or Weck (German) brands, both of which are widely available in many parts of the world. You can buy new lids and rubber seals as you need with both brands. I prefer this over the cheaper generic brands, where it’s usually necessary to buy a whole new jar and lid together. You can use any clean jars with undamaged lids, just be aware that lids which have been used before may not seal as consistently as new ones.
If you plan to do a lot of preserving, it’s also handy to have a decent wide-mouth funnel for filling jars without making a mess; buying one of these was a gamechanger for me because it saves so much time wiping around the rims of the jars.
Sanitizing jars for use
Before you fill and process your jars, they need to be sanitized to kill lurking bacteria which will spoil your carefully prepared food. This be done in your steam oven using the full steam setting (212°F/100°C, 100% humidity) for 20 minutes. Heat the upturned jars on a perforated tray and lids/seals on another, and don’t let them touch one another. I sanitise and if I’m not quite ready to fill, leave the jars in the turned off oven until I need them so they remain hot.
Some people refer to sanitizing jars as sterilizing, which is literally making something sterile, removing all traces of microbes from a surface. Because steam ovens are used for cooking other types of foods, and have many crevices and places for bacteria to hide, it’s not possible to completely sterilize in one (even if your oven is very clean!). Sterilizing isn’t something most of us can achieve at home by any method and sanitizing is just fine for most home preserved foods anyway.
How long can you keep preserved foods?
If cooked and sealed properly, most things you’re preserving in a steam oven will keep for a year or more in the pantry. Once they’re opened, you should store the jar in the fridge and consume it within a couple of weeks.
Jar filling, sealing and storage tips
- When filling your jars with food, leave a little room at the top; around ½ inch/1.5cm is good. If you’re adding a syrup or pickling liquid, pour it over your produce so it just covers, not so the jar is overfull. That little bit of space allows for air to escape from the jar during heating.
- Once your jars are full, put lids on and tighten them to ‘fingertip tightness’. This means tightening to secure, but not screwing them tightly on with all your strength so that no air can escape from the jar.
- Jars which are sealed properly after processing will have lids which are slightly concave, with no movement or popping sound when you press down on the centre of the lid. If the lid gives when pressed, it’s not sealed.
- Usually, a jar that’s not sealed either hasn’t been heated for long enough, or the top rim wasn’t completely clean when the lid went on, leading to food becoming stuck between the glass and the seal. It’s important to wipe any spillage from the rims of filled jars with a very clean, damp cloth before putting lids on and heating.
- If you preserve a batch of food and end up with any jars which have not vacuum sealed properly, store those jars in the fridge and eat within a week or two.
- If you think you’ve just not heated the jars for long enough and want to attempt a second go at sealing, you can try running them through your steam oven again. Only do this if the foods within aren’t too delicate. I would try re-sealing with a chutney or pickle, but not a berry jam, for instance, where the colour and flavour of the jam will be less appealing the longer it’s heated.
- Occasionally you might open a jar that appears to have been sealed properly only to find it’s got mould on top. This is usually caused by not having properly cleaned jars or lids, or not having heated the food inside for long enough to kill all the potentially harmful bacteria. Some people simply scrape off the top layer of food and proceed to eat as normal, others (including me) recommend discarding the whole contents of the jar to be on the safe side.
More resources for canning and preserving
If you missed it above, here’s the pdf I created for you, with guideline times and temps for steam oven processing.
Additionally, these are a few links I’ve found helpful for learning more about preserving, and which I’ve applied to preserving in a steam oven. While they don’t refer specifically to steam oven settings, you can adapt the water bath times and temperatures referenced to achieve the same results in your steam oven.
Bottling and canning general overview, with various methods and links. I find all sorts of useful things on this UK-based site, it’s super practical and in-depth.
Slow water bath bottling/canning. From the above allotment gardening site, this is an excellent guide for conversion to your steam oven, as the processing is done at a lower-than-boiling temperature. Lots of helpful times given for specific fruits.
Bottling (canning) tomatoes the Australian way. I absolutely love this no-nonsense video guide to water-bath tomato processing. In fact, if you have any interest in homesteading in general, subscribe to the YouTube channel and follow along for lots more Tasmanian farm-life adventures and how-to’s for what to do with excess produce.
5 Responses
Great article Emily – thank you!
Oh, that’s great to hear! This is definitely a subject I hope to expand on in future, because it’s a great way to modernize a more traditional type of cooking. About all I can preserve at the moment is citrus or apples, and I’m eagerly awaiting more fresh produce come spring/summer here.
Jan, I had you in mind when I was writing this – I did not forget that you’d requested something on this topic, it just took a while to pull it all together! Glad you enjoyed it.
Great article thanks Emily.
Great info! Thanks. This is going to make my preserving life much easier, especially sterilizing jars and doing the water bath canning. I am entering the major preserving season (Northern Calif.) and was going to cut out some of my canning, but may end up doing more! I love what you’ve done with the Insiders portion of your website. It is so much easier to find recipes, etc. Thank you!