Most anchovies you encounter in stores have been salt-cured for months, a process that transforms the raw fish into the intensely flavored, umami-rich fillets used on pizzas and in sauces. The method hasn’t changed dramatically in centuries: fresh anchovies are layered with salt, pressed under weights, and left to mature. What happens during those months is a slow enzymatic breakdown that creates the anchovy’s signature taste. Here’s how the entire process works, from the boat to the tin.
Catching and Initial Handling
Anchovies are small, perishable fish that begin to deteriorate quickly after harvest. Once caught, they’re immediately chilled and stored in refrigerated holds or ice bins. Speed matters here because anchovies are especially prone to producing histamine, a compound that builds up in fish tissue as bacteria break down an amino acid called histidine. Regulatory limits for histamine in anchovy products are strict: in the U.S., the FDA flags products at 35 ppm, and the EU caps fermented anchovy products at 400 ppm. Keeping the fish cold from the moment of catch is the primary defense.
Heading, Gutting, and Sorting
At the processing facility, the fish are sorted by size. This step matters because uniformly sized fish cure at the same rate. Workers or machines then remove the heads and entrails, a step sometimes called “nobbing.” In large-scale operations, automated nobbing machines handle this. Smaller, artisanal producers still do it by hand.
The internal organs are removed for a practical reason beyond cleanliness: the gut contains powerful digestive enzymes. While some enzymatic activity is desirable during curing, too much from the viscera would cause uncontrolled breakdown of the flesh. The cleaned fish are then rinsed to remove blood and residual tissue.
Salt Curing and Layering
This is the heart of anchovy processing. The cleaned fish are packed in alternating layers with coarse salt, typically at a salt-to-fish ratio of about 1:4 by weight. So for every four parts of fish, one part of salt is used. The fish go into barrels, tins, or large vats, and heavy weights are placed on top to press them down.
The salt does three things simultaneously. It draws moisture out of the fish through osmosis, creating a brine that submerges the fillets. It inhibits the growth of harmful bacteria. And it creates the right environment for a slow, controlled protein breakdown called proteolysis.
During proteolysis, enzymes naturally present in the fish muscle, primarily alkaline proteinases, gradually break down large protein molecules into smaller peptides and free amino acids. Research on European anchovies shows a remarkably linear relationship between this protein breakdown and ripening time: the longer the cure, the more complete the transformation. Scientists can actually track ripening progress by measuring the ratio of non-protein nitrogen to total nitrogen, which climbs steadily month after month.
The Ripening Period
Traditional anchovy curing takes anywhere from 6 to 12 months, though some producers extend it further. During this time, the fish undergo dramatic changes in color, texture, and flavor. The flesh shifts from silvery-pink to a deep reddish-brown. The texture firms up and becomes more uniform as water leaves and proteins restructure. The flavor intensifies enormously.
The flavor transformation is largely about free amino acids. Glutamate, the amino acid responsible for umami taste, becomes the dominant free amino acid in ripened anchovy products. In Italian anchovy sauce studied over a 48-month maturation period, glutamate concentrations ranged from 0.56 to 0.73 grams per 100 milliliters, with significant increases between 12 and 48 months. Aspartate, another umami-contributing amino acid, followed the same upward trend. This is why aged anchovies taste so much more complex than younger ones, and why they function as a flavor amplifier in cooking.
Filleting and Packing
Once the curing is complete, the anchovies are removed from their barrels and separated into individual fillets. Workers pull the spine and tail bones from each fish, usually by hand, since the small size makes mechanical filleting impractical. The fillets are rinsed to remove excess salt and any remaining scales.
At this point, the product takes two main paths. Some fillets are packed as “salt-packed anchovies,” returned to tins or jars with more salt. These are the whole-looking, bone-in fillets you find in specialty stores, and they tend to have the most intense flavor. The other path leads to oil-packed anchovies, the more common supermarket product.
Oil Packing and Its Purpose
For oil-packed anchovies, the rinsed fillets are carefully arranged in tins or glass jars, then covered with oil. The oil serves as more than a flavor medium. Its primary preservative function is insulating the fillets from air, preventing the oxidation that would turn the fish’s fats rancid. The oil doesn’t actively kill bacteria, but by creating an oxygen-free seal, it dramatically slows spoilage.
The type of oil matters. Studies comparing extra virgin olive oil, regular olive oil, and refined seed oil in canned fish found that extra virgin olive oil produced the least fat degradation by a wide margin. Secondary oxidation byproducts measured just 0.17% in extra virgin olive oil compared to 0.50% in regular olive oil and 0.74% in refined seed oil. This is one reason premium anchovy brands use extra virgin olive oil, and why those products tend to taste cleaner and last longer.
Canning and Sterilization
Once filled, the tins are sealed using a process called double seaming, which crimps the lid tightly to create an airtight closure. The sealed cans are washed, then sent through a retort, essentially a large pressure cooker that heats the cans to temperatures high enough to destroy any remaining bacteria. After retorting, the cans are cooled, labeled, packed into cartons (either by hand or machine), and shipped.
This thermal processing step is what gives canned anchovies their long shelf life, often two to three years. It’s distinct from the months of salt curing that happened earlier. The curing develops the flavor; the retorting makes the sealed product shelf-stable.
Anchovy Paste and Fish Sauce
Not all anchovies end up as fillets. Anchovy paste is made by grinding cured fillets with salt and sometimes a small amount of oil or vinegar into a smooth, spreadable consistency. It’s essentially the same product in a more convenient form.
Fish sauce takes the fermentation process much further. Rather than curing whole fillets for months, fish sauce producers allow anchovies to fully liquify in salt over one to four years. The liquid is strained off and bottled. The extended fermentation produces even higher concentrations of glutamate and other umami compounds, which is why a few drops of fish sauce can transform a dish.
What Happens to the Waste
Anchovy processing generates significant waste: heads, tails, bones, and viscera. Increasingly, processors convert these leftovers into valuable byproducts rather than discarding them. One approach uses enzymatic treatment to break down the protein-rich waste into hydrolysates, powders containing small peptides and free amino acids. Research on anchovy waste hydrolysates has produced dry powders where essential amino acids make up 42% of total amino acid content, a nutritional profile promising enough for use in functional foods or as standalone supplements. Traditional uses for anchovy processing waste include fish meal for animal feed and fertilizer.