CHAPTER 3 Salting of Herring N. A. VOSKRESENSKY Scientific Research Institute of Marine Fisheries and Oceanography (VNIRO), Moscow, U.S.S.R. I. Introduction 107 II. Methods of Salting Fish 108 A. Types of Salting 110 III. Characteristic Features of Salting Ill A. Salt Penetration HI IV. Technological Aspects H9 A. Salting Technology 121 References 128 I. Introduction The salting of herring is intimately connected with the development of marine fishing. Comparatively large quantities had to be preserved not only on shore, but also out at sea. In the twelfth and thirteenth centuries, production of herring in the North and Baltic Seas was already on a rather large scale (Noel de la Moriniere, 1817; Samuel, 1918; Cutting, 1955). The salting of herring was probably first practiced in Scotland in the eighth century. Afterwards, in the fourteenth to sixteenth centuries, this method was improved by the Dutch and Scotch and also by the Russians, working independently (Noel de la Moriniere, 1817; Dosipheus, 1833; Maksimov, 1872; Samuel, 1918; Jarvis, 1950; Cutting, 1955). In Russia, the barrel salting of herring was originally employed in the White Sea area by monks of the Solovetsky Monastery (fifteenth century). Whole herring were salted with small quantities of salt. The fish were packed in barrels in regular layers, and each layer of herring was sprinkled with salt. Contrary to the methods used in the countries of Western Europe, a barrel of rather small size, containing 10 kg., was used for the salting of herring. Such a barrel was called "seldyanka" (Danilevsky, 1862). After being filled, the barrels were tightly sealed to prevent spoilage and possi­ bly also to achieve better ripening. They were then buried in the ground, which kept them at an almost constant temperature of 0°C. In later times, special vaults were dug in the ground for this purpose. During the summer season these were cooled by ice. Salted herring of the Solovetsky 107 108 Ν. Α. VOSKRESENSKY Monastery were distinguished by very good quality and, judging by their method of preparation, were similar to the Dutch, which in Western Europe have always been considered the best. The so-called Anzersky herring, from the Gulf of Anzersky in the Solovetsky group of islands in the western part of the White Sea, oif the city of Kern, were also of especially good quality (Dosithei, 1833; Semenov, 1859; Danilevsky, 1862; Maksimov, 1872; Minder, 1948b). If the salted fish did not have a specific odor and soft consistency, the Russians were unwilling to buy such fish, claiming that the "fish was not ready," that is, according to the terminology of our time, had not ripened. Up to the end of the eighteenth century, in the diet of the Tsar's family and well-to-do classes of the population of Russia, the salted herring of foreign import (even Dutch and Scotch) were used very little. At this time, the salted fish of domestic preparation was particularly valued and most readily purchased (Chulkov, 1781-1788; Semenov, 1859; Kostomarov, 1862; Zabelin, 1872). In the eighteenth century two distinct branches of the herring indus­ try emerged, one based on catching the fattening herring in the open sea, and the other on spawning herring coming in large shoals to the coast and even entering the rivers; the vats or bins1 and the pile type of salting were employed. II. Methods of Salting Fish Salting is a method of preservation based on the penetration of table salt into the tissues, and governed by various physical and chemical factors such as diffusion, osmosis, and a series of complicated chemical and biochemical processes associated with changes in various constituents (chiefly protein) of the fish. Salting starts the moment the fish surface comes into contact with salt. The condition of the salt does not matter, whether in crystals or in solution. Under practical conditions the salt treatment is initiated when the vat, barrel, or other container is filled with fish and salt. The end of the salting process is the moment when all the fish have reached the required salinity and acquired the appropriate taste, consistency, and odor. Japanese researchers (Murata and Ohoishi, 1953) established the fol­ lowing relationship, which describes the concentration limit to which the fish must be salted in order to keep: S χ 100 = 50 W —35 1 In the Soviet Union a square vat of very large size is called a bin. 3. SALTING OF HERRING 109 where S is the content of table salt in the meat (in %), and W is the content of water, free and bound, in the meat of the salted fish (in %). Upon attaining the limit (characterized by the number 50), the bac­ terial activity (decomposition) in the meat of the fish has been stopped. Different procedures are in use for the salting of herring, the selection depending upon the climatic conditions, character of the industry, and the organization of the salted herring trade specific to each country. The most common procedure is to employ containers such as vats, bins, and barrels (Voskresensky, 1958, 1960). The vat has been widely used by the fish industry of many countries since the middle of the nine­ teenth century. In Russia, for example, this coincided with the period when, particularly on the Volga, the Astrakhan fish industrialists began to pack herring in salt in massive quantities. This sharply decreased the rendering of fat from the fish. Norway considerably expanded her fisheries in the fjords in order to salt herring. Partially subterranean vats were used, easy to assemble and dismantle. This is important in areas where the herring does not regularly approach the shore. The salting of fish in vats was quite a favored method in some coun­ tries for the following reasons: (1) In the case of large fisheries, the migration usually is of short duration and massive character, especially during the catch of spawning herring; in order to process quickly large quantities of fish (about 100,000 lb. per day and per enterprise), simple and spacious installations are indispensable. Vats meet these requirements effectively. (2) In the majority of cases, especially in areas with a warm climate, it is necessary during the salting to chill the fish with ice. In vat-type salting, it is easier to do this by interspersing the fish layers not only with salt but with ice; in barrel-type salting this is almost impossible. (3) With the arrival of fish in large quantities, it is quicker to salt in vats than in barrels. Unit consumption of labor in a vat salting process is less than when barrels are used. The drawbacks of vat salting are the unequal degree of preservation, due to the height of the vat, and the pressure exerted on the fish during salting. Both of these are serious, especially in the salting of fat fish with tender meat. During recent years, with the greater mastery of herring fishing in the oceans, vat-type salting is gradually losing its prior significance in both the U.S.S.R. and other countries. It is being replaced by salting in barrels. The difficulty of mechanizing the packing of raw fish in the barrel and the low productivity of labor during this operation are the basic factors holding back the introduction of a barrel-type salting of herring in fish factories on the shore during the major herring migration. 110 Ν. Α. VOSKRESENSKY Α. TYPES OF SALTING Since ancient days there have been three basic methods used in the salting of fish; in most countries these methods are distinguished as (1) dry, (2) wet, or (3) mixed. Dry salting is characterized by the fish being salted with dry crystal­ line salt. A solution of salt is formed in the water extracted from the fish. The salt, as a result of its hygroscopic ability and osmosis, absorbs the water from the fish and is then dissolved by it. This solution of salt has received in the U.S.S.R. the name of natural "tuzluk" (salt brine). The dry method of salting is used mainly in the barrel salting of herring. Wet or salt brine type of salting is a process by which the fish is salted in a previously prepared solution of salt. In this method the fish is immediately put into the salt solution, which gives the method the name "wet." It is seldom applied for the salting of herring, and then only in preparing a lightly salted product. The basic deficiency of wet salting is a rapid decrease in the original concentration of salt brine in the preserva­ tion process. The adding of salt to one of several places in the vat in order to prevent the decrease in concentration of salt brine does not give the needed effect, because the process of diffusion, which tends to equal­ ize the concentration of salt brine in the vat or barrel, takes place very slowly. This causes unequal fish preservation. Considering this deficiency of wet salting, Τ. M. Borisov (U.S.S.R.) in 1939 proposed that salt brine be continuously driven by a pump around the layers of fish. In a special apparatus (concentrator), the concentra­ tion of salt brine is brought up to the saturated condition and the salt brine is again used for salting. This method is known as salting in circu­ lating salt brines. It is used in the Soviet Union during the mechanized vat salting of herring in the coastal fisheries (Berezin, 1951; Voskresensky, 1958, 1960). Mixed salting is a method by which the fish is salted simultaneously with salt and with brine. The fish is rolled in salt, loaded into the vat or barrel, and a certain amount of salt solution is added.