Published On: Thu, Feb 19th, 2015

Preserved or Semi Preserved fish. Is there a difference?

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Preserved or Semi Preserved fish. Is there a difference?.

conservas_denticiPreserved and semi preserved goods are a staple in the pantry of Spanish and some European countries’ households, being a fundamental part of these countries’ diet.

However, in some countries canned food is considered to be low quality product. This is far from reality: The fish canning process meets all the health and product quality needs.

Canned goods are obtained from perishable foods of animal or vegetal origin, placed in glass jars or cans, sealed and thermally treated (steam) so conservation is guaranteed.

Preserved food is treated with autoclave at 115°-125°C (239-257°F), a machine used for sterilization and sealing purposes. It  inactivates all fungi, bacteria and viruses that can be resistant. At Conservas Dentici-Olasagasti the temperature in the autoclave is set between 110°-130°C (230°-266°F). And depending on the format of the product, we need different lengths of time for the sterilization process.

At this stage, commercial sterilization is achieved after having erradicated the heat–resistant bacteria. This bacteria may alter the quality of all preserved goods and also pose a risk to the consumer with the development of the dangerous agent known as Clostridium Botulinum, which can cause the infrequent but serious disease known as Botulism. The main source of infection by this agent is more frequent when canning goods, such as vegetable and and fruits, at home. For this reason and in order to avoid any health risk it is advisable to get this process carried out in specialized firms.

The quality of preserved goods does not decrease over time and it must be said that these products do not have an expiration date but a “best before” date.  The only requirement to maintain the high quality is to store the cans and jars in a fresh but dry place as we do with sauces, veggies, tuna, albacore, etc. In our case, Olasagasti’s preserved fish (white tuna, mackerel, bluefin and yellowfin tuna) have a best before date of 6 years when processed in olive oil, and 5 years in the case of al naturel, pickle sauce or catalana sauce.


Let’s learn about semi preserved goods. The difference between preserved and semi preserved goods lies in the treatment that they follow. Semi preserved goods do not have any thermal treatment and the preservation is based on salting, smoking or drying.

Anchovy fillets are cured with salt and canned within an expiration date of 10-18 months. Even though semi preserved anchovies do not perish once the expiration date is up, after 8-12 months the quality suffers, the meat shows some discoloring and it loses its firm texture. Therefore, it is best to keep the semi preserved anchovies in the fridge and consume them within the first months of canning to ensure its quality and flavor.

If you have any doubt, our recommendation is always the same, check the labels for the right period and temperature of conservation. In most cases, when we go grocery shopping we find semi preserved anchovies and sardines stored in the fridge  but it is also easy to find these products on regular supermarket shelves. We must say that this type of storage is correct although they could be exposed to direct sunlight and temperature changes that can affect the quality of the product. We would suggest to store these types of products in the fridge and once they are open, to consume them within a few days.

Often times, we get asked about the container we use to preserve our products and the reasoning behind our choice… a can or  jar? What is better? We have to say that the container does not alter the quality of conservation of the good and that the procedure is the same, it’s actually a matter of likings.

Personally, I don’t care if the tuna or peppers come in one format or in the other. It is true though that jams, fish or veggies seem more attractive if they come in a jar but I have to say that I am loyal to the brand I like, no matter the container they present their goods in. The convenience of the container and the ease of handling is what I look for. Quality and convenience.

What we have to look for, it’s the state of the can when we purchase it and open it. The tin should not be buckled or the product dry , foamy or smelly; if this is the case, we should throw away the can right away.  A mistake within the distribution chain, during transportation or a mishandling by the seller or consumer when storing a preserved and semi preserved good, can ruin months’ of artisanal work.

I must say that even if these cases happen, they are not as common as they seem and preserved and semi preserved goods are absolutely safe to consume and thanks to its elaborate and technical production methods, they can keep their organoleptic properties on, a fact to remember as many households keep preserved and semi preserved foods as staple goods in their pantries.

Now it’s your time. It’s your time to choose between a high quality preserved and semi preserved good or a “regular one”. It’s the time to make a choice. Not every preserved and semi preserved good has the same quality and production method and it’s up to you to make the right choice. The same happens when we freeze high quality meat, fish or bread we expect to find the same quality once we take it out; But if we put mediocre quality goods in the freezer we won’t find an extraordinary quality good after we defreeze it, the taste won’t be exceptional and it may lose nutritional value.


It’s your choice; our commitment to quality is aimed to you.
Be our guest. Believe in us. We offer quality, safety and flavor!
Marta Olass & Olasagasti family.

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