How to safely sterilize your homemade preserves

As much as the world and technology advance, today, like yesterday, we still want to enjoy homemade preserves, taking advantage of seasonal fruit and vegetables to consume throughout the year. The conservation techniques are various, from dehydration, lactofermentation, vacuum or canning in a bain-marie as before, which we are going to focus on in this article.

6 tips for safer home canning

Whether for jams or fruit compotes or canned tomato sauces or boiled vegetables, the sterilization phase of the jars is the most important of the process because it is where we most guarantee the absence of risks and germs, although the cleanliness and quality of all the elements must exist at all times.

1. Choose food in perfect condition and wash it well

Extreme hygiene in each manufacturing step to prevent the multiplication of some bacteria which can be toxic. This includes washing products, work surfaces and the instruments we use.

2. Check the glass jars that we will use and disinfect them

They can be washed by hand with soap and water, but most effectively in the dishwasher, oven, or, if reused and not new, boiling them in a saucepan covered with water, for about 20 minutes from the boil.

Cleaning the oven consists of introducing the clean and dry glass jars into the tray with the oven previously preheated to 170ºC and leaving them there for about 10 minutes.

To preserve the jams we recommend small size jars because they cool faster and keep better. If they have a wide mouth, handling is easier.

3. Make sure the can is well covered

The caps require special attention because must close hermetically without leaks for the correct conservation of the preserve. Ideally, use new covers and clean them well. If they are old, they should be boiled like boats. There are 3 types of tapas to assess:

The classic screw caps Those that include a sealing button in the center of the lid. Once the vacuum is made, the button is partially sunk inwards. The glass lids with staples and sealing rubber in which it is easy to check if they work or not because when opening the staples the lid is well stuck if it has been produced correctly the vacuum.

4. Carry out a correct filling

When filling the jars with jam or preserves, you must be careful not to burn yourself. The funnels that can be adapted to the jars make this task much easier by avoiding spills and risks.

Canisters need to be filled almost completely to prevent environmental bacteria from entering, but leaving a small gap near the edge so that a vacuum can be made.

Although it is popularly considered that filling the jars with very hot jam or sauce is sufficient because the heat destroys the germs and the vacuum is created when turning the container over, for greater safety we recommend boil the jars afterwards to achieve higher temperatures.

5. Apply the sterilizing heat well

The last part of the process is the most important because it is where conservation is most at stake.

The traditional and simple method by applying heat is called “water bath” and consists of exposing the products to be preserved at a temperature above 70-90 ºC, with which most of the germs and bacteria responsible for fermentation or food rotting are destroyed.

Can place a cloth rag between the boats inside the casserole to avoid friction between them and possible breakage due to thermal shock, although it is not usually necessary.

It is convenient remove the preserves after boiling and avoid leaving them in the casserole because some microorganisms have their best point of development at temperatures between 40 and 70º. We are looking for rapid cooling.

When taking them out, we put them upside down on some rags or cardboard to Check if any of them have not been well sealed and liquid is coming out. If so, the vacuum has not been made and must be stored in the fridge and consumed in the following days.

To help us remove the boats from the boiling water, there are specific tongs for canning. We can also use heat-resistant kitchen gloves, although sometimes they do not allow a good grip. Be careful.

Can we use the pressure cooker?

Although it is not the most used option, with the express pot we achieve better hygiene and conservation results. in his book natural preservesthe expert Mariano Bueno explains that it is one of the safest methods for a good sterilization because by increasing the pressure, the temperature easily reaches between 120 and 160 ºC and in these conditions it is possible to completely sterilize the preserves and minimizes the risk that appear Clostridium botulinum, the feared cause of botulism.

In these pots it is recommended isolate the jars from the bottom with a cloth or a rack and use for 10 to 20 minutes after the steam has come out for proper sterilization.

electric pasteurizer

There are also specific household appliances for boiling preserves, such as pasteurizers, which have advantages over conventional casseroles due to its larger size, temperature control, cleanliness because splashes are avoided, efficacy and safety.

The pasteurizers are programmed, They turn off automatically and have a small tap for the water outlet.

In addition to pasteurizing preserves, they are also used to prepare broths and stews or stews.

6. Label the preserves

We must not forget to label our jars to identify what they are and the date of production, because sometimes several harvests come together and it is always necessary to give priority to the previous ones.

How to avoid botulism and contamination

The safety of preserves is a recurring issue because there are different microorganisms that can cause food deterioration such as yeasts, molds and bacteria, but the latter are the great threat to our preserves as they are resistant to heat.

Molds and yeasts die from 60ºC, but bacteria withstand higher temperatures and develop, without the need for oxygen, in low-acid (alkaline), humid and closed environments, such as those in canned food. Hence the need to respect all phases of the process and sterilize at high temperature, first the empty containers and then with the preserves inside.

The disease that generates the most fear when dealing with these issues is botulism, caused by a toxin produced by the bacteria Clostridium botulinum. This toxin can be found in poorly prepared preserves, both in a water bath or by vacuum systems, in low-acid canned foods that have been subjected to inadequate heat treatment, in some meat products, non-chlorinated water, or by inhalation.

One has to discard unceremoniously preserves that have a swollen lid, that give off strange odors, that make a kind of foam or that gas comes out when opened.

Enjoy preserves for months

It is recommended to store homemade preserves in a dark, cool and dry place because moisture promotes mold growth.

In general, They keep perfectly for more than a year and some much more, but each case must be assessed because low-sugar jams and compotes have a shorter life.

Once opened, the preserves are exposed to environmental bacteria, so they must be consumed within a few weeks and always store them in the fridge.

With all these tips, today, as in the time of grandmothers, we can continue enjoying seasonal fruit jams during the rest of the year.