Another page here covers the history of Salsa Espinaler. But it might be a good idea to do a hands-on review, in order to give a sense of what to expect. The sauce was devised by one of the owners of the Espinaler Tavern in Spain in the 1950s as an "appetizer sauce" to be used primarily on a variety of tinned seafood. I obtained a bottle from an online source after an unproductive search of local stores.
At first glance, the sauce looks like a typical hot sauce, but less viscous. There are quite a bit of extremely fine, undissolved solids-- mostly red, but some black. Some settle to the bottom of the bottle and a good deal which appear to remain in suspension.
Instructions say to shake well before using, and to refrigerate after opening. My guess would be that if used up quickly enough, refrigeration might not be necessary. There doesn't appear to be anything that might cause rancidity.
Taste Test
First, I tasted the sauce by itself, a few drops on a spoon. The shaker top dispenses only a few drops-worth per shake. The initial impression is very vinegar-forward, probably a cider vinegar unless the other ingredients are doing something to alter the flavor of a plain distilled or spirit vinegar.
The next impression is of a slight saltiness. The label says that, among other things, the sauce is "not a significant source" of sodium (or anything else). At half a calorie per tablespoon, we'll just have to guess that some salt is among the unnamed "spices".
There is a very faint heat to the sauce. The second ingredient is red pepper, and it is evident in that it sticks to the sides of the bottle, much like that of a typical hot sauce. But it isn't the primary flavor note.
If you think about it, many condiments have a strong vinegar component: ketchup, mustard, pickle relish, salad dressings. Or perhaps more accurate to say an acid component, as, if not vinegar, lemon or lime juice. Acidity can cut through richness, can "wake up" taste buds.
Salsa Epinaler reminds me in some ways of a simpler version of an Eastern North Carolina barbecue sauce. In that region, "barbecue" is whole hog pulled pork, seasoned with a thin, vinegar-based sauce containing salt and spices like cayenne, paprika and chili powder. Nothing like the thick, sweet sauces popular in other barbecue meccas like Memphis, Kansas City or Texas.
So far, I've tried it on plain sardines, smoked oysters, plain mackerel and calamari. I think it brings an interesting dimension to tinned seafood, and keeping a bottle on hand is worth considering.
Other Variations
A second, "hot" version adds cayenne, and a third adds habanero for an extra-hot experience. There's also a fourth, an organic version of the regular flavor that, like their organic tinned fish products, is labeled "BIO"; a sea green colorway serves to differentiate those products.