Preserving food is a great way to make sure that the abundance from your garden doesn’t go to waste. Find five food preservation methods explained.
Preserving feels kind of scary doesn’t it? When it’s done wrong it can make whoever eats the preserved food very ill.
Today my guest and dear friend Sarah Christofides explains five food preservation methods and shows that preserving food is fun and much less complicated than it seems!
When I saw Sarah last, I asked her about preserving. I myself am very slowly dipping my toes into the waters of preserving and since Sarah is a lecturer in Bioinformatics and a PhD graduate in fungus-bacteria interactions in decomposing wood she was the perfect person to ask about it.
A very interesting conversation followed and she explained everything so clearly and with such passion that she definitely took some of my fear around preserving away.
Today’s guest blogger Sarah Christofides.
After our conversation I asked her whether she would be willing to share some of what we talked about on here.
I am grateful that she agreed to it and I hope that this blog post will give you the confidence to have a go at preserving your own food.
FIVE FOOD PRESERVATION METHODS EXPLAINED
At the height of summer when the waves of fresh produce unfold, there is a great deal of pleasure in planning not just how to use this bounty now, but how to keep it for later.
Preserving may seem an intimidating prospect if you’ve not tried it before, but at its simplest anyone is capable of producing home-made treasures to keep and use at any time.
The heart of preserving is preventing food from spoiling due to the growth of micro-organisms.
As my microbiology lecturer put it, food goes off because “other things like to eat the same food that we do”.
Preserving keeps food delicious and safe by staving off the little blighters through one (or a combination) of the following mechanisms:
HEAT
Many preserving techniques use heat to kill off micro-organisms before sealing the produce in airtight containers, and almost every preserve will be stored in jars that have been sterilised using heat.
Hygiene is of utmost importance when preserving, but don’t be intimidated: just make sure that everything you use is spotlessly clean, and once something has been heated to sterilise it, don’t let it cool down until safely sealed.
Obviously, this will only be effective if the container is airtight once closed.
You can buy new empty jars for preserving, but the cheapest and easiest way is to collect used jars. They will be quite safe so long as the lid still fits tightly and hasn’t rusted.
To get a good tight seal, make sure that the lid is fitted straight so that it screws properly into the thread, and screw it as tight as it will go.
For preserves that are jarred hot, you can check the quality of the seal by looking at the safety button on the jar lid.
If it pops down as the jar cools, the seal is intact. If it remains raised, you know that the seal has not formed properly and the contents will need to be used up fairly soon.
Always do a sniff-test when reusing a jar: if you put your jam in a container with a lingering scent of pickled onions, expect the result to be… interesting!
OSMOTIC POTENTIAL
This is a technical way of saying that there is a lot of salt or sugar present.
Salt and sugar both draw out moisture: this is why we salt aubergines to remove excess water, and why sugar will go clumpy if not kept in a dry place.
Put a lot of salt or sugar in a preserve and any lingering microbes will have all the water sucked out of their cells, which is about as detrimental as it sounds.
ACIDITY
Every organism has particular range of pH in which it can survive. Cover your produce in vinegar and it will immediately be out of acidity range for many microbes.
ALCOHOL
Alcohol is actually produced by a particular group of micro-organisms, the single-celled fungi called yeast.
However, it is toxic to other microbes (and even to the yeast that make it when it reaches high concentrations).
Even if you don’t drink alcohol, do not discount this method of preserving. Alcohol has a low boiling point, so if you cook an alcoholic product you will drive off the alcohol and keep all the other flavours.
COLD
In the polar regions, there are microbes that can grow at the -20°C temperatures typical of a domestic freezer. It is unlikely that any of them will be living in your fresh produce.
Freezing may be a relative newcomer on the preserving scene, but it is a very effective way to keep produce.
Just bear in mind that produce will not be crisp after defrosting, as the ice crystals damage the cells. For this reason freezing is best suited to produce that will subsequently be cooked (like vegetables) or blended (like fruit for smoothies).
Hopefully this will have whetted your appetite for trying preserving for yourself!
If so, I recommend getting a good book on the subject with recipes that will walk you through the process step by step.
My personal go-to is River Cottage Handbook: Preserves by Pam Corbin, but there are plenty of options available: go to a bookshop and have a flick through some options to see what takes your fancy.
Then take the plunge and lock up some summer goodness for yourself!
