CROSTES, PITIUS ENDEMISM

The wonderful thing about much of traditional Balearic baking is that, much like certain species of animals or plants on these islands, having lived in literal isolation  for a long time, they have gradually diverged from their mainland relatives to become true endemics – in some cases unique rarities, in others isolated vestiges. These living fossils tell us what baking was like in times gone by and are authentic relics of a bygone and primordial way of understanding bread.

Crostes are part of an ancient seafaring tradition which, though it may sound curious, was the norm in any seaport, not just in the Balearic Islands. As bread spoils easily with time and the humidity on board, to stock the ships’ pantries, the technique of baking the bread twice until it was completely dry has been used since ancient times; this is where the word biscuit (bizcocho in Spanish) comes from, which is still used in Formentera to refer to the crosta. This term is related to the Italian biscotti, the French biscotte and the German Zwieback. In Spanish, the full name is “costra de bizcocho,” as the bizcocho was not a soft sweet, but pieces of bread baked twice (bis-coctus). To eat this bread, there are still people in the Balearic countryside today who preserve the ancestral custom of soaking the crostes before eating them, just as a sailor would The best-known way to eat them is in the classic summer salad, where the tomato juice, together with the dressing, soaks into the crosta until it rehydrates just enough to be soft on the palate yet retains its crunch on the inside.

In the past, crostes were synonymous with bread of necessity, as can be read in the seafaring chronicles of the heroic age of navigation. In the General History of Chile (1884), Diego Barros Arana wrote the illuminating phrase: “Shortly afterwards, provisions became so scarce that the travellers had no food other than a few biscuit crusts”. Similarly, in Catalan, the expression for the total absence of food is “no haver-hi pa, ni vi, ni crostes” (there is neither bread, nor wine, nor crusts).

A tradition across many seas

Although for centuries they were consumed by peasants and people who needed long-lasting bread, these crostes have ended up becoming the staple food of crews, which is why their trail can be traced across various seas. Without leaving the Mediterranean, in Greece we find paximadia (with a Protected Geographical Indication on the island of Crete), which forms the basis of dakos, a sort of Hellenic version of the Balearic peasant salad, although there, in addition to tomato, it is eaten with cheese, and the piece of bread is used whole rather than chopped. In some forms, the resemblance between paximadia and crosta pitiusa is striking.

Without even leaving Spain, we can find crostes in other seas; it is no coincidence that the only region in the country where the tradition of eating twice-baked bread is still alive is the other archipelago; there, a similar product is known as “pan bizcochao”, and in the Canary Islands it can be found in many variations, both flavoured and made with other ingredients such as maize or even potato.

The mystery of crostes: the science of starch

Why do crostes and other breads such as biscotes have a delicate crunch, whilst stale bread is as hard as a rock? To understand how twice-baked bread works on the inside, we need to understand what happens to the starch in the crumb. The moment the bread comes out of the oven, two separate phenomena begin to occur: drying (obvious to the naked eye) and the retrogradation of the starch (more difficult to see). This second phenomenon occurs because starch tends to return to its natural state, in which, before swelling in the presence of water and heat, it is actually hard. A crust of bread left in a drawer is both dry and has undergone starch retrogradation. However, if you take a freshly baked loaf, with its starch structure freshly swollen and spongy, and dehydrate it completely at that moment, you achieve the magic of preserving the delicate structure of the fresh bread’s starch, but without the water. That is why a crosta made with freshly baked bread has a delicate crunch, whereas one made with bread that has been left to stand for a few hours is much coarser – which is what happens when the bad practice of toasting bread that has been left out all day and, having failed to sell, is now being turned into crostes, is followed.

Interestingly, starch retrogradation is a reversible process, and this is what happens when we put a piece of bread that is a few days old into the toaster; its starch has retrograded, but it still retains some moisture inside: when the starch is reheated and becomes a gel, it regains the soft, creamy texture it had when it left the oven.

Ibán Yarza, is a journalist, writer, and populariser of bread culture