In Denmark, the typical starter served on Sunday meals and Christmas lunch consists of pickled herring on sourdough rye bread, served with a side dish of fresh onions. Before the fifties, every housewife knew how to prepare them, buying salted herrings, which were stored in wooden barrels, then preparing the fillets and desalting them in water or buttermilk to remove the slightly rancid flavour of the fish. The brine was made by boiling together sugar, water, vinegar, bay leaves, mustard seeds, black pepper and allspice. Then the desalted fillets were marinated in this brine along with onion rings, from a minimum of two days up to a maximum of two weeks. From that point onwards, these household operations became increasingly rare, and industry slowly took over the production process, so much so that now marinated herrings can be found in all supermarkets, packaged in glass jars or tins.
Towards the end of the sixties, the practice of storing salted herrings in barrels had all but disappeared, preferring a faster technique with very different results: seasoning in vinegar. The method of storing in barrels with salt makes a difference compared with its industrial counterparts. Salted herrings stored in barrels have a natural brown colour, whereas those pickled in vinegar are whiter due to the acid’s bleaching effect. The consistency is also different: the former are tender and firm, the latter are soggier, to the extent that they easily turn to mush. Additionally, the former are much better at absorbing the flavours of the brine, and generally lend themselves to more interesting recipes.
The traditional production method is more ancient and dates back to a thousand years ago, when there was a thriving herring trade between Iceland and Denmark, and involved arranging the freshly caught and pickled herring in barrels, layering fish with salt. The right season for fishing is autumn, when the fish fat content is at its peak. At regular intervals, the barrels are rolled and turned upside down, in order to ensure a proper salt distribution and fish ageing. Optimal flavour level develops at 6-8 months after start of operations; in the past, even a year went by—i.e. the start of the following fishing season–before they were sold and eaten.