Dear readers, I would like to provide you with all the information and instructions to microwave in jars safely: which jars are adequate to put in a microwave oven, the capability and cooking times, how test your
own microwave, what kind of food microwave, and above all which are the precautions to microwave with the vasocottura* technique.
If you want to know more about it go on reading this article.
*The term cannot be properly translated in English because it’s a technique created in Italy.
During these years I figured out that every microwave oven is different depending on its capacity, on
how distant from the glass turntable the magnetron is, on how much the oven breathes and on the
material is made. All these diversities give a different power even though the power indicated is the
same. The age of the microwave oven can play an important part because of the magnetron which is
subject to exhaust just like a battery.
After 3 years of study I understood how to ensure the same results to all the people cooking with my
technique. With a simple water test you can find your own tested power. I give you an example: my
tested power now is 750 watts, with my old microwave oven it was 800 watts, while the power of the
microwave oven I use to teach in my classes is 600 watts. All these 3 powers give me the same result
with the same time cooking.
How do you test your own microwave oven?
The answer is very simple: you will only need a jar of 500 ml, fill it up with almost ¾ of water at
room temperature, close the jar, put it in the microwave oven and then start for 5 minutes with a
medium power. From the third minute it is necessary check the water in the jar because you need to
verify when it begins to boil. If the water starts boiling between 3 minutes and a half and 4 minutes
and a half, the power you are using will be your tested power. Obviously if the water begins to boil
before, you will have to retry the water test at a lower power, but if the water boils after 4 minutes
and a half you need to retry the test at a higher power. In case you don’t have a microwave oven with
adjustable powers, you can adjust your aim by verifying the beginning and add 2 minutes more
(these instructions are usable for the jar of 500 ml).
Why is it important to follow the cooking times?
In order to get a vacuum-packed that allows us to preserve our recipes for 15 days, we have to boil
the content for 2 minutes. You can also get an extended post-cooking when you microwave in jars of
500 ml for 6 minutes. That permits us to cook ragù, stew and recipes that have long cooking times.
Which are the things that can compromise the vacuum-packed?
The vacuum-packed can be compromised by old, worn-out and/or damaged rubber seals. Deformed
clips and dirty edges. The cooking with few watts doesn’t create the vacuum-packed, which permits
a long conservation. Don’t be tricked by the lid which doesn’t come off, there can only be a mild
Maintenance, washing and conservation of clips and rubber seals
Besides Weck stainless steel 18/10 clips, which can be washed in the dishwasher, I recommend you
washing clips and rubber seals by hand. The latter need to be hung up and fully dry up. You don’t
have to reassemble the rubber seals when you replace the jars otherwise, they can lose volume and
produce bad smells and mould. At the first use I suggest degreasing clips and joints because
companies to cut them grease the parts. Greases are conductors and these can create sparks.
Jars that can be used and their capacities
Weck, Bormioli Fido line, Ikea’s Korken, Le parfait with the hook top and Kilkner are the jars
brand I tested. However, there are jars perfect for some recipes and not for others. For example,
Weck’s jars are ideal when we want to interrupt the cooking, for sweeties and for short cooking.
Instead, Bormioli’s, and Korken as well, are perfect to cook ragù, stew, thin dishes and all those
foods which need long cooking.
Just like for the burners cooking times are different based on the capacity, the same thing happens in
the microwave oven. So, a jar of 500 ml will microwave, on average, for 6 minutes, while a jar of
one litre will microwave for 12 minutes.
You must avoid putting metal objects or whichever jars on the microwave oven because the
proportion of aluminium and the shape they have could create sparks. By saying that all metals can
go on the microwave, is like saying that no metal goes on the microwave. There are some varieties of
jars suitable for microwaves; there are also different rubber seals, which are not mentioned in this
article, that can’t support the heat or that can compromise the vacuum-packed. The jars became like little pressure cookers, so they DO NOT HAVE TO BE OPEN before the formation of the
vacuum-packed – which is created in the next 20 minutes of the cooking. Moreover, in many
recipes during the stand the cooking finishes. Hearing a whistle throughout the cooking is
normal! The excess vapor vents through the rubber seals by producing a natural whistle. For
this reason, the jars can’t explode!
DO NOT USE JARS WITH SCREW TOP: there isn’t a good coming out of the vapor in excess.
o a jar of 350 ml circa cooks for 4 minutes – water test in 2 minutes;
o a jar of 500 ml cooks in 6 minutes – water test in 4 minutes;
o a jar of 750 ml cooks in 9 minutes – water test in 6 minutes;
o a jar of 1 litre cooks in 12 minutes – water test in 8 minutes.
These times don’t have to be considered for desserts, milk products and fruits, so it is for the tested
power. Indeed, the food listed must be cooked at half the time and power.
Which food you can cook in vasocottura?
Many types of food are perfect for the vasocottura. Green light to fish but you must pay attention to
crustaceans and shellfish which cook in a short time.
Have fun with vegetables from side dishes to savoury pies, from parmigiana to pureed soup and
For meat there are pieces of meat more recommended but others hard to tenderise. Instead, white
meats are good: chicken, rabbit, pork meat.
Also, green light to all the types of meatballs and rolls.
Pay attention to milk products and eggs which can be ruined by the high powers because of the
greasy they contained.
Say yes to lasagne but be careful to pasta. A lasagne can be frozen while we wouldn’t do that with
pasta. So, we could cook a plate of pasta, but we can “only” keep it for 8 hours. Approximately, the
pasta that has a cooking time of 12 minutes, we can perfectly cook it in 6 minutes.
Another chapter are cereals or such: you can used rice but parboiled, because a rice not treated with
vapor cannot be cooked in vasocottura. Quinoa and barley are good but spelt and all the cereals that
cook in more than 30 minutes.
They say that mushrooms cannot be cooked in vasocottura but it is not true. A friend of mine, a
mycologist, clarify any doubts: if mushrooms are toxic, they remain toxic even if they cooked in a
frying pan. It isn’t true that the toxins disperse with the vapor, so the mushrooms can be cooked in a
For the potatoes there are many items to clarify: potatoes cut into pieces cook perfectly in
vasocottura; while potatoes cut in thin slices, they remain al dente. That depends on the percentage
of the water they released: if you want to cook delicious potato pies you need to parboil the potato
slices before going on with the cooking in jar. You need to remember that potatoes keep better for a
Bones can be cooked in jar if they are covered by the meat or immerse in broth.
Where do you buy jars for the vasocottura?
You can buy Wecks on the website Decorazioni Dolci, to the members of my assistance group is
applied a 10% discount; you can find information on the group or contact me on my Facebook page.
The website sells jars with 4 clips as my technique requires.
You can find Korken at Ikea while Bormioli Fido are on Italian supermarket, hardware, garden
centres, Amazon and on their official website.
Why do all these recipes keep better in fridge?
The vacuum-packed and the jar sterilization it isn’t like the classical preserves. The Local Health
Authority has made test on recipes cooked with the vasocottura technique: if the jars are conserved
in the fridge and cook following my instructions after 10 days there isn’t bacterial proliferation.
To know more…
If you want a personalized assistance subscribe on my Facebook group Vasocottura Facile
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