Tag Archives: Techniques

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.
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.
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.
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.

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.
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.
Label and store the jars in a cool dark place. They will keep for several years
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.


Preserving Tomatoes

28 Aug

Tomatoes make some of the most valuable preserves and condiments for the pantry; sun dried tomatoes, passata, tomato concentrate, sauces or salsas, and chutneys. Processing tomatoes for preserving can be a messy time consuming affair and the kitchen can look like a set for the chainsaw massacre but for me the rewards are worth it, It is such a luxury to have all this lush tomato stuff in the cupboards because lets face it we won’t be seeing tomatoes again until next July unless I can get some to ripen a little earlier next year. Each year I grow more and more tomatoes so that we will have enough to preserve. We eat so much of these tomato preserves that there is just never seems to enough until next years crop.

The all purpose preserve is the basic sieved tomato sauce called Passata, to take the Italian name for it, just tomatoes boiled with a little salt and then sieved or put through a pasta machine. It is indispensable in the kitchen as a base for all kinds of dishes. For full instructions on making passata see How to Make Passata.


It has more body than sieved tomatoes and very useful pantry preserve. The process is slightly different from passata in that the tomatoes are skinned and de-seeded then chopped.  This is the basic stuff I have left over from seed saving and as a seed saver for Association Kokoplelli I tend to produce a lot of this. It can be used fresh in its basic state, frozen as is or bottled cold and heat processed. I usually cook it to reduce the amount of liquid in the pulp before bottling into 250g jars with a sterilising lid and heat process for 20 minutes.

Many sauces that we regularly make can be heat processed. Tomato sauce differs from passata in that the tomatoes are cooked with other ingredients and it is not sieved so it has more body and is perfect to use straight from the jar on pasta or in other dishes that require a tomato sauce. See my Basic Tomato Sauce recipe.

Drying tomatoes is like alchemy the fruit wither down but their flavour just gets bigger and more intense. It is best to use a fairly dry type of tomato or the drying process will take forever. A good tip is to place the tomatoes on a metal surface as the heat reflects back and speeds the drying process up.


This is the cheapest method of drying tomatoes requiring no real apparatus but it does require sunshine. Slice plum tomatoes length ways, remove the green pithy stem sprinkle with salt and lay cut side up on a slatted tray or basket. Cover the tray with netting or gauze to keep insects out. Position the tray in the sun during dry sunny days and bring indoors when the sun goes down. If the weather is at all damp bring the tray indoors and sit on a sunny window still making sure there is plenty of ventilation. It takes about 3 days but could take a little longer depending on the weather and how dry you want the tomatoes. Dust off the salt and store packed into sterilised air tight glass jars in a cool dark place.

Follow the same method as above but place the cut tomatoes on a large oven tray and place at the bottom of an oven set low. I normally set our oven between 50c and let them ‘dry’ for anything up to 24hrs. The length of drying time will depend on: the type of tomatoes, your oven and how soft you want to have the tomatoes.

I use usually use San Marzano plum tomatoes for this recipe. Follow the oven drying method as above but you want the tomatoes to be slightly soft, in our oven 50-75c for 6-8 hours works. Dust off any excess salt and pack into hot sterilised glass jars. Cover with olive oil to 1 cm above the tomatoes, tap gently to knock out any air and seal immediately. Store in a cool dark place. These make wonderful hors d’oevres or tapas straight from the jar and a real treat in winter.

I tried freezing tomatoes after reading Susan’s post on Farmgirl Fair Preserving the Harvest: How to Freeze tomatoes the really easy way. It sounds too simple to be true but often the most simple things are the best. All you do is wash the tomatoes, chuck them in a bag then put them in the freezer. Done! Great tip- Susan thanks.

This is the most complicated and time consuming of the tomato preserves. Concentrate is basically passata reduced down to become a thick paste with a very concentrated flavour. It takes a lot of tomatoes to make a small jar of paste but if you like tomatoes it is worth it. I could eat this stuff just spread on bread.
To Make roughly chop ripe tomatoes, cutting off any bad bits, and chuck them into a large pan. Season well with sea salt and cook over a low heat for 20-40 minutes giving it a good stir every now and then so that it does not stick. The tomatoes should disintegrate and become pulpy. Cook for longer if not. Let it cool slightly then pass the pulp through a passata machine or a sieve pressing it with the back of a spoon until all that is left in the sieve are skin and seeds. Return the sieved tomatoes to the pan (after first rinsing the pan) and cook over a low heat until it is reduced. It should reduce to a thick dark red paste. You will know when it is thick enough when you can draw a spoon through it and the sauce does not run back into the channel left by the spoon. When the paste is the right consistency spoon it into sterilised jars, add a layer of olive oil to cover the paste and seal immediately. Store in a cool dark place and refrigerate once opened.

For information on growing conserving tomatoes go to www.masdudiable.com 

How to Make Sweet Preserves

1 Jan

Most fruit can be preserved using sugar and it is pretty easy to turn a glut of seasonal fruit into all kinds of  jams, jellies, curds, butters, pastes and marmalades. It is a great way to conserve fruits when abundant for use later in the year when there is non. Here are all the basics you need to know plus some of my favourite recipes.

What fruit to use

My favourites are: apricot jammirabelle jam, quince jelly, red currant jellyplum butterfig jamquince cheese (membrillo), raspberry jam, blackcurrant jelly and lemon curd.
There is no point making sweet preserves unless you or your loved ones like eating it. For instance I won’t be making grape or white mulberry jelly again as they were too insipid, or pear jam as it had no flavour, or cherry jam as I didn’t much like the taste, or elderberry jam which really was foul, or rowan which was weird but of course it is all a matter of taste so experiment with what you like.

1. Wash and chop (unless it is already small) the fruit removing peel, cores, stones or pips where necessary.
2. Put fruit in a large pan with a little water, bring to the boil, then simmer until soft.
3. Add sugar and stir until dissolved.
4. Increase the heat and boil until setting point is reached.
5. Pot up into sterilised jars & seal 


Large heavy bottom pan or jam pan.
Long handled wooden spoon, the longer the handle the less likely you are to burn yourself when stirring hot jam.
Jam jars and covers. 
Nice to have

Jam Funnel – A jam funnel is very handy, its like an ordinary funnel but with a wider neck that fits inside a jam jar making it easier to fill.
Jelly Bag- a specially made bag that can be hung up and left to drip separating the juice from the pulp only required for jelly making and even then a piece of muslin can be used.
Cook’s or sugar thermometer 

You can use glass jars of any size, make sure the ones you use don’t have any cracks, chips or flaws.  For sweet preserves I generally use fairly small 250g jars, as we don’t get through jam very quickly this size is ideal for us and they are also an ideal size for presents. If you eat larger amounts of jam use larger 450g/1lb jars or whatever you have to hand. It is possible to buy jam jars in France at agricultural shops and even in supermarkets which is what we do because we don’t have many jars to hand not buying the stuff that normally comes in them, however if you do just wash and save the jars with their lids to use later for your own preserves. Ideally you will have saved the lids with the jars and can use those other wise it is possible to buy wax paper and plastic jam pot covers (personally i don’t find these as successful but worth having a go if you can find them). They come with instructions so just follow 

The most important thing is to make sure that all the equipment you are using is scrupulously clean and that the jars and lids the preserves will be kept in are sterilised. 
  Prepare the jars by washing them well in warm soapy water and then rinsing thoroughly. 
Oven Method

This is my preferred method once the jars are washed put them on an oven tray and place in the oven (160C, 335F, Gas Mark 3) for 10mins. Leave to cool slightly but fill whilst still warm to prevent the jars from cracking when the hot filling is added. This requires timing, put the jars in the oven about 15mins before you think the jam will be ready to pot up. 
Hot Water Method

Place the jars carefully in a large pan, cover with water and bring to the boil. Once boiling continue boiling rapidly for 10 minutes, remove the jars carefully, shake off any excess water and set out to dry on a heat proof tray, the heat in the glass will help evaporate the water if you need to speed drying up just pop them in a warm oven until all the moisture has gone. 
 Bring a pan of water to the boil, drop the screw top lids into the water and  boil for 5 minutes, strain, shake off excess water and leave to dry just prior to use. A simpler method is to pour boiling water over the lids and leave to steep for 10 minutes, drain and dry before use.
Rubber seals and corks.
  If you are using kilner jars or jars with cork tops, they need to be sterilised slightly differently. Bring a pan of water to the boil drop the seals or corks into the pan and boil for 1 minute and remove from the heat. After another 5 minutes drain and leave to dry ready for use.

There are 3 methods to test if setting point has been reached. I would generally use at least 2 to be sure. 
1.        Wrinkle test
 – This is the easiest and most reliable test all it requires is a cold saucer (put a saucer in the freezer for 15-30mins). When you think the jam may be ready, remove the pan from the heat. Drop a teaspoonful of jam onto a cold saucer. Allow it to cool for a few minutes then gently push your finger through the jam. If it wrinkles a satisfactory set has been achieved. If it doesn’t, return the saucepan to the heat and continue to boil for a few more minutes then test again. Repeat as necessary. 
2.        Flake test – 
Dip a spoon into the jam, remove it and after a second or two tilt it so that the jam drips. If the drips run together and fall from the spoon in flat sheets or flakes then setting point has been reached. I personally find it hard to decide if the jam drips in flakes or just drips so only use this as a second test. 
3.        Temperature Test
  Jam reaches setting or jelling point at between 104 and 107 degrees Celsius  making sure the jam reaches this temperature requires a cook’s or jam thermometer. Place the thermometer in a jug of hot tap water to warm up the thermometer so that the sudden temperature change dropping it into the jam does not crack it. Place the thermometer into the pan without resting on the bottom, they often have some kind of hook to hang onto the side of the pan so that the thermometer does not reach the bottom of the pan. This is the most accurate method but only really useful if you are making large quantities and you have to buy a thermometer. 

Fill the jars while they are still warm from sterilisation with hot jam (jam should be hot but not still boiling, leave it to cool slightly for a minute or two before filling). With or without a funnel carefully spoon or pour the hot preserve into the jars, filling to just below the top, wipe any stickiness from the rims of the jar with a clean damp cloth and seal.  To seal jam i just screw on the sterilised lid and my jams have lasted well for 3 years so far. However, if you are in any doubt about the keeping ability of the jam (say you have added even less sugar or only barely cooked the fruit in order to retain more of its fresh taste), there are a couple of things you can do to keep air away from jam to stop it spoiling. Before putting the lid on cover the surface of the jam with a disc of grease proof or waxed paper cut out to fit the jar pressing it down so that it has contact with the warm jam or add a thin layer of brandy to form a barrier between jam and air, then screw on the lid.


Label with the contents and date. It is very easy to make your own labels so why not make your jam labels look nice while your at it. We made some particularly nice ones by cutting disks out of brown wrapping paper and hand writing the label then gluing it on with pritt stick. You can also make labels on the computer, which is what i do now, using a basic wordprocessing package. 

Most jams are ready to eat immediately but can be stored for 2-3 years. Store in a cool dark place and, once opened, keep in the fridge.

This article was originally written on www.masdudiable.com in August 2006, I’ve re-written it and re-posted this new updated version.  

How to Make Wine Vinegar

1 Jan

It is really worth making your own wine vinegar because the home made stuff is delicious and if you can wait long enough it is far better than anything you can buy. Making wine vinegar is really simple you just need a little ‘mere‘, some wine and lots of time.

The mere or Mother of Vinegar is an Acetobacter, a useful bacteria that turns the ethanol in wine to acetic acid with the aid of oxygen.

Just before we left England to come to France one of our friends, Jean Yves, a Frenchman, gave us a parting gift. Something we would need in France. Jean Yves scooped some weird looking sludge from a large white crock he had on his kitchen counter and put it in a clean jam jar. This sludge would not have looked out of place in a 50’s sci-fi movie, but this stuff was precious. Jean Yves had given us some ‘mere’ or mother so that we could make our own wine vinegar.

He also told us how to make wine vinegar, the instructions are simply to put the mere into a jar with a loose cover or vinegar pot and add wine then leave it until it turns into vinegar.

Once we were in France I bought a vinegar pot just like the one Jean Yves had at a local market. A vinegar pot is normally ceramic with a loose fitting lid and tap. The tap means that you can decant the vinegar without disturbing the sediment and the mere, and makes it easy to test a little bit to see if is ready to decant.

Testing a small amount of vinegar to see if it has matured enough to be ready to use.

I put Jean Yves’ mere into the pot along with a little bit of red wine. My biggest problem was parting with the wine to turn it into vinegar but I decided to use the dregs from each bottle of red we drank along with a few sloshes of stuff I wasn’t so keen on drinking. Admittedly not much hit the reject seat so it was a while before the vinegar jar was full. But once it was full I left it alone and waited. I left it for three years before tasting it and found it had turned into wonderfully sweet, rich red wine vinegar. I decanted it, through a filter, into a special red wine vinegar bottle, an old ceramic one I had found, with a spring top. The bottle is perfect, not only does it stop the light and keep the vinegar well it looks pretty in the kitchen or on the table.

How long does it take?

It took 3 years for my first batch of red wine vinegar to mature to my taste but that’s nothing apparently. I was at my neighbours house recently and discovered his red wine vinegar has a vintage of over 30 years, it knocked the socks off mine and was truly delicious. If only I could wait 30 years. Some people reckon it only takes a few months to turn wine into vinegar and that may be so but from a taste point of view the longer it ferments the better the taste seems to get.

Red and White

As luck would have it I ended up with another vinegar pot from Rachel’s sister exactly the same as the first one so I now have two jars, one of red and one of white wine vinegar, fermenting away.