How to make homemade preserves. Image: Kolpakova Svetlana – Shutterstock.
If we want to make preserves at home and among other things, reduce food waste, we must take into account some procedures to follow to prepare jams or tomato sauce without incurring the risk of food poisoning.
There are those who have their own garden, those who have a reputable retailer or those who buy fruit and vegetables from the supermarket. The result is the same: many people, these days, are busy in the kitchen preparing the preserves for the next few months.
The best way to preserve food. But with preserves, no joke: the biggest risk is botulinum toxin poisoning. But it can also happen that you wait several months and then discover that your preserve is inedible.
Precisely for this reason, you must follow some guidelines to eliminate, or at least reduce, any risk, even for home canning.
Canning is made to preserve food from normal spoilage processes, which can be caused by microorganisms, enzymes, or physical agents such as heat and light.
The bogeyman is Clostridium botulinum, a bacteria that produces a toxin that is very dangerous for humans: it can cause gastrointestinal disorders and in some cases even death. Its symptoms appear between 12 and 24 hours after consumption. If the pasteurization went wrong, after a few months the product could smell bad, like gas: it is the result of the action of microorganisms that have not been eliminated. This, however, is only discovered after opening the bottle.
The first tip is to start working with clean hands, in a clean environment, and with clean tools. Wash your hands before handling food and always after coughing or sneezing. Also be careful with cloths and sponges, they constitute the greatest danger of the spread of microorganisms and require frequent disinfection and replacement. It goes without saying that the containers should also be cleaned, washed with water and detergent, and dried thoroughly before use. Those who sterilize empty containers in a water bath, on the other hand, do not need to dry them.
It is preferable to use glass for canning. It does not absorb odors, can be reused countless times, and can be washed and sterilized. The only downside is that it lets light through, which can alter the product. That is why glass jars should be stored in the dark.
You also have to be careful with the choice of closure system. The safest are metal capsules, but systems with rubber seals and hinges are also good. Capsules and gaskets must be replaced each time they are used. Avoid using damaged or rusty caps. To cook the preserves, instead, you should choose a stainless steel pot. Neither aluminum nor copper.
Homemade preserves. Image: casanisa – Shutterstock.
Whether it is fruits or vegetables, we should give preference to seasonal ones and preferably local ones, or at least those from your region or country. The shorter the distance traveled by the product, the lower the risk that it will undergo preservation treatments prior to sale.
To wash fruit or vegetables, a good method is to blanch them: in boiling water for a few minutes (the precise minute depends on the food) to eliminate the residues of soil and microorganisms.
After blanching, the vegetables should be cooled immediately by soaking them in cold water to prevent them from losing their consistency due to heat.
We always talk about “sterilization”, but the term is not entirely correct. Sterilization is a very difficult process to do at home because it involves treatment times of more than 5-6 hours. What we do at home is disinfect : we fill the jars with water that we then bring to a boil. An unnecessary operation, however, if the jar has to be filled with cold products: just wash and dry.
Pasteurize the preserves.
This is perhaps the most delicate phase of all : a mistake could compromise preservation and make the product inedible. The containers – now full – must be immersed in water, the level of which must exceed the cap by 5 centimeters. To prevent the containers from hitting each other during boiling and breaking, cloths can be placed between them.
But how long should the boiling process take? For low-acid preserves (for example, those containing meat or fish), between 7 and 11 hours. That is why it is advised not to prepare at home. For acidic foods (tomato sauce but also jams and preserves) it takes between 5 and 85 minutes, calculated from the moment the water boils.
Once the pasteurization is finished, you can remove the jars to let them cool wrapped in a wool blanket. Or you can leave them in the water after you have turned off the fire.
Check before the pantry.
After 12-24 hours of pasteurization, it’s time to check the metal caps. If they are bent inward and do not move when pressed, the air has been removed and pasteurization went well. If, on the other hand, the center of the lid is not concave and clicks under finger pressure, it means that pasteurization has failed and you have to start over. Or consume the product in that week.
If you are using lids with a safety lock and a rubber gasket, you can check the tightness and vacuum by removing the safety lock and trying to open the lid by applying light pressure. If the lid does not hold, it means that it is not hermetically sealed and it is not vacuum sealed.
When the lid is removed, it should be stored in the refrigerator and consumed as soon as possible. However, storage times vary depending on the content. Products in oil or vinegar can remain up to two months; jams (which are those of citrus), jams (which are prepared with all other fruits) for a week Sauces should be consumed within 4-5 days.
How to make canning at home.
Guides for the preparation of home canning:
- FAO: Guide to good practices for the preparation of canned vegetables.
- Ministry of the Environment Spain: Guide to Good Manufacturing Practices in the Transformed Vegetable Sector.
- Agriculture Ministry Argentina: good practices guide canning processing.
- National University of La Plata: Canning preparation course.
- Reference booklet for preserving vegetables and fruits from the garden.