How to Preserve by Heat Processing

15 Mar
Heat processing is a form of preserving foods by putting hot, warm or cold foods into a container and heating until any bacteria that might be within the food or container is killed and a vacum is achieved. It is a very useful technique for the kitchen gardener, no glut of produce need ever go to waste and can be stored for times when there are less fruit and vegetables available fresh from the garden or market.
HEAT PROCESSING
The simplest way to achieve this on a domestic scale is to use glass jars, with lids and heat the jars and their contents in boiling water, the ‘hot bath method’.
Preparing the food
Food can be processed from cold or hot. I only use the hot method, cooking the fruit of vegetables before bottling, as this is the most reliable way to ensure food does not spoil and can be stored safely.
Jars 
You need to use jars that can be heat processed such as; ‘mason’ jars which come with a two piece lid, a domed cap that fits tightly on the neck of the jar and a screwband which fits over the cap and is screwed down onto the jar, kilner type jars which have a clamp down glass lid sealed with a rubber ring, or simple glass jars with special lids. I buy 250g jars from our local agricultural store that sell different types of lids including those for heat processing. The jars can be re-used as many times as they remain sound. Jars must be scrupulously clean and without any flaws, cracks or chips as any flaw could result in the galss shattering while being heated.
Lids
The lids are the important bit, when heat processing the lids need to allow for the expansion of air and liquids and then the function to tighten or lock to seal and make a vacum.  The basic lids are those with a circular dimple which become depressed during the process indicating that a vacuum has been achieved. There are also 2 part lids and clamp lids. It is essential to purchase new lids or seals for each use.
Filling Jars
Pour the hot food e.g. tomato sauce, passata, salsa, cherry compot whatever it is into the prepared jars, leaving a 1cm gap at the top, screw the lids on well but not too tight.

Equipment
There are special heat processing pans available but I find using a pasta pan with a draining insert works just as well particularly if  I am only processing small batches. The pan I have was not expensive, I bought it in Ikea at least 10 years ago, and it will fit 5 x 250g jars comfortably.
Heating
Carefully place the jars in a single layer around the sieve part of the pan then lower into the outer pan. Fill with hot water to 2 inches bellow the lids, and bring to the boil. Once boiling cover with a well fitting lid and set a timer for 15-20 minutes. When the timer goes off raise the draining insert and set down with the jars inside. Use a towl to protect your hands from the heat, tighten all the jars. If used kilner type jars adjust to final lock down position. Set aside to cool. The airlocks in the lids should all depress as they cool which indicates a full seal. If any do not depress repeat the process.
Store
Label and store the jars in a cool dark place. They will keep for several years
Warning
If dimples in the lids rise again this is a sign that air has entered the jar and the food may have spoiled. Do not consume as there could be a risk of botulism.
Note Make sure you follow the instructions that come with the type of jars you have purchased, as each jar type will have its own sealing mechanism.

Advertisements

One Response to “How to Preserve by Heat Processing”

  1. Laura 15/03/2012 at 10:41 #

    someone left this comment on my old blogger site so i thought I should paste it up here – as it is useful info and point taken i’ve changed the tags – those slight differences in language can be quite tricky.

    Thank you so much! I looked for this all over the web and couldn’t find it. It isn’t politically correct in the U.S., but I find their fear mongering a little too idiotic.

    I’m still using my grandmother’s canning book from the 1940’s. Been using it for over 30 years and still haven’t had any dreadful results from it.

    I see that when you “bottle” tomatoes you leave the water below the lid, where here, water has to be at least an inch above the lid or it’s considered unsafe.

    Also, the scare mongers are telling people that they have to use either lemon juice or vinegar to can tomatoes.

    Our department of Agriculture had a Q & A area on their site. They had changed some processing times on green beans. A woman posted that she had canned 250 quarts of grean beans from the prior season and wanted to know if it were safe to use.

    The idiots told her to throw them all out!

    I briefly saw the preserved paste done on a cooking show, wrote it down and lost it when I moved.

    I currently have a yard full of canning (Rutgers) and paste (Roma)tomatoes growing and now live in sunny Florida which has nice hot summers in which to dry tomatoes.

    Again, thank you so much for posting this information. Could you please use the word ‘canning’ in your keywords and your recipes so that other Americans can find it?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: