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Preserved or Semipreserved fish. Is there a difference?


Preserved and semipreserved 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 areas 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.


Olasagasti canned bluefin tuna, artisanal product, quality preserved or semipreserved fish

Olasagasti canned Bluefin Tuna, caught one by one in August. Photo by Virginia Martín.


Preserved food is treated with autoclave at 115°-125°C (239-257°F), a machine used for sterilization and sealing purposes. It erradicates 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.

Women working at Olasagasti factory: preserved or semipreserved fish

Autoclave at Conservas Dentici-Olasagasti factory.


At this stage, commercial sterilization is achieved after erradicating the heat–resistant bacteria. The 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 condition known as Botulism. The main source of infection by this agent is more frequent when vegetables and fruits are canned 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.

Women working at Olasagasti factory: preserved or semipreserved fish

Women working at Olasagasti factory. Are they preparing preserved or semipreserved fish?


The quality of preserved goods does not change over time and in fact there is not an expiry date but a “best before” date on the labels. The only requirement to maintain the best quality is by storing the cans and jars at room temperature (in a fresh and dry place) as we do with sauces, veggies, tuna, sardines, and so on. As far as Olasagasti products are concerned, preserved fish (white tuna, mackerel, bluefin and yellowfin tuna) indicate a best before date of 6 years when processed in olive oil, and 5 years in the case of in brine, pickled sauce or catalana sauce.

Yellowfin tuna: preserved or semipreserved fish? It is preserved fish.

High quality preserved fish is an excellent option to add to vegetables for a healty diet


As for semi preserved goods, the difference between these and preserved goods lies in the treatment they undergo. Semi preserved goods do not need any thermal process and the preservation is based on salting, smoking or drying.

Anchovy fillets are cured with salt and canned within an expiry date of 10-18 months. Even though semi preserved anchovies do not perish once the expiry date is over, it is true that after 8-12 months the premium quality diminishes: the flesh loses intensity in color and texture. Therefore, it is best to keep semi preserved anchovies in the fridge and consume them within the first months of canning to ensure maximum quality and flavour.

Anchovy fillets: preserved or semipreserved fish? It is semipreserved fish.

Olasagasti Anchovies are perfect for Spanish tapas. Semipreserved fish.


In case of doubt, our recommendation is always the same: check the information on labels. In most cases, when shopping for groceries we find semi preserved anchovies and sardines stored in cold chambers although these products can be found on any supermarket shelf at room temperature: The latter option is quite commun although for keeping the maximum quality of this product we would recommend storing in cool places.


Focaccia with Olasagasti Anchovy fillets, mozzarella, tomato and pesto sauce.

Focaccia with Olasagasti semipreserved Anchovies, mozzarella, tomato and pesto sauce.



In cans or in jars? Which is best? We have to say that both containers are perfect to keep premium quality and all properties.

As far as I am concerned, I don´t mind if tuna o peppers are sold in jars or cans. It is true that jam, fish or vegetables look more attractive when presented in jars. However, I tend to be loyal towards a brand I appreciate, no matter the container if it has been well conserved, kept and stored.

There again preserved and semi preserved goods are absolutely safe for consumption, moreover they keep all their organoleptic properties, a fact to take into account since these are staple in almost every houshold.

Preserved or semipreserved fish? High quality preserved fish in tins

High quality preserved fish in tins


It’s up to you now to choose between high quality preserved and semi preserved goods or any other average quality product. The time has come to make up your mind: Not all preserved and semi preserved goods offer the same quality or processing methods. The same thing happens when we freeze high quality meat, fish or bread: we find the same quality once defrosted, whereas when freezing poor quality products, we find the same poor quality defrosted products.

Preserved or semipreserved fish? High quality preserved fish in jars

High quality preserved fish in jars


Our aim is to offer premium quality… then you decide.

We are inviting you to be our guest, to trust and enjoy the result of our professionalism.


Marta OlassOlasagasti family

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