[Advances in Food Research] Advances in Food Research Volume 4 Volume 4 || Fish Preservation in Southeast Asia
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Fish Preservation in Southeast Asia
BY A. G . VAN VEENl
University of Delft, The Netherlands Laboratory of Biochemistry
I. Introduction . . . . . . . . . . . 11. Fish Sauces . . . . . . . . . . .
111. Fish Pastes . . . . . . . . . . . IV. Salted Fish, Not (or Partially) Dried . . V. Salting and Drying . . . . . . . .
VI. Miscellaneous. . . . . . . . . . . VII. Summary and Conclusions . . . . . .
References . . . . . . . . . . . .
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. . . . . . . . . . . 217 . . . . . . . . . . . 2 2 1 . . . . . . . . . . . 225 . . . . . . . . . . . 227 . . . . . . . . . . . 2 2 8 . . . . . . . . . . . 229
The total protein content of the diets of millions of people living in Southeast Asia is low, especially when it is compared with standards commonly accepted in North America and Western Europe ; the animal protein content is even lower. The reasons for the poor protein supply are numerous and will not be discussed in this article.
One of the most important sources of animal protein in Southeast Asia is fish. One of the best possibilities for raising the animal protein level of the diets in that part of the world is to increase the consumption of fish, both the salt-water and fresh-water varieties. Fish, either fresh, dried, o r salted, or in the form of a paste or sauce, is a common ingredient of the rice-eaters diet. However, the relatively high price of fresh fish and the limited supply of fish products, as well as their poor keeping quality and the inadequate marketing systems, have all hindered a greater consumption. Even along the coastal areas and the numerous rivers and lakes as well as in the neighborhood of fish ponds the con- sumption is frequently lower than would be expected. This is due partly to lack of efficient fishing equipment and to unsatisfactory methods of preservation.
At present with the Nutrition Division, Food and Agriculture Organization of the United Nations, Washington, D. C. ; formerly Director, Eykman Institute. Batavia, Indonesia.
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During the Southeast Asia Fisheries Conference (held in Singapore i n February, 1947) possibilities were discussed for increasing the supply of fish fourfold (to 4 oz. per capita per day for the nearly 650 million people living in that area). The Fisheries Meeting, convened by the Food and Agriculture Organization of the United Nations in Baguio, Republic of the Philippines, February, 1948, also stressed the desirability of considerably increasing fish production and discussed the possibilities of bringing it about.
Increasing fish production would of course be of limited value unless a t the same time efficient methods of preservation are adopted SO that sup- plies can be made available to the large population living beyond the fish- ing centers. I n northern countries, this may not be a problem ; in Southeast Asia, however, where the climate is hot and damp and thus favorable to spoilage, it is a very great one.
Canning, freezing, and icing, which are simple and relatively cheap methods of preserving fish in Europe and North America, are generally too expensive in Southeast Asia. The economic level of most of the population living in this region is very low; retail prices must also be very low if fish consumption is to be encouraged. Even the very cheap Japanese canned fish products, available in the area before World War 11, were usually too expensive for the great mass of the population. This is still true for all imported fish and fish products ; hence only very few people can afford to buy them.
Another problem which must be taken into account when considering fish preservation problems in this region is the fact that the tastes and food habits of the rice-eater differ from those of the American or the European. Their diet (most of the inhabitants of Southeast Asia are rice-eaters) is usually monotonous. It is an important fact that the rice- eater prefers to eat his rather tasteless rice mixed with little spicy morsels of salted fish, fish paste, fish sauce, curries, Spanish peppers, etc. Ordi- nary canned or frozen fish lacking pronounced flavors cannot replace these primitive fish products (as flavoring agents). This does not mean, however, that canned or frozen fish would not be acceptable in South- east Asia. On the contrary, once the requirement for a flavoring agent has been met, there is generally a demand for more animal products; however, dried fish, salted and dried fish, and pastes and sauces are the usual forms for preservation in these and other underdeveloped coun- tries. Even so, fish in these forms are subject to the action of numerous microorganisms, especially a t temperatures and humidities prevailing in this part of the world. The microorganisms ma.y come from the en- trails, the gills, and the slime of the fish, may be introduced with salt, air, etc. Many food products of high nutritional value prepared in this
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area and subjected, intentionally or otherwise, to the action of bacteria, yeasts, or fungi would be called spoiled or even decomposed in the West. Microbial action and spoilage are usually considered more o r less synonymous (except in such foods as cheese, sauerkraut, and yo- ghurt) and are often associated in the mind of the consumer with food poisoning. Such, however, is not the case in Southeast Asia.
Many casual and superficial observers would be inclined to think that the only cheap and simple methods of fish preservation would be simple salting and/or drying. In a tropical climate one would suppose that, because of infection by numerous microorganisms, rather strong smelling products would result. They might also believe that the local consumers would, therefore, by sheer necessity become quite accustomed to the resulting flavor, appearance, etc. Without doubt there is some truth in this; however, the person who has an intimate knowledge of the fish markets in this area, and who is acquainted with the local production, marketing, and consumption habits and problems, or has studied these fish products, knows that the consumers are able to distinguish between many different grades and qualities. Fish is not bought just as i t is found on the market, but by very careful choice, determined by a num- ber of factors. The manufacture of fish products is not done haphaz- ardly, and the buyer is discriminating in his choice of products. It is said that an experienced fish dealer can often detect the presence of very low concentrations of calcium and magnesium in the salt used because of the differences in taste, texture, etc., of the fish products.
The quality of many of the fish products under discussion is influ- enced not only by the method of preservation and the kinds of micro- organisms present but also by such factors as the nutritional status of the fish (fat content, etc.), the activity of the enzymes in the tissues (autolysis), and the impurities present in the salt. I n this connection, it may be useful to remember that part of the texture and taste of pickled herring in the Netherlands is attributable to the enzymes orig- inally present in the pylorus of the fish, which is retained during the gutting operation (Liebert, 1924).
Microorganisms often play a considerable role in fish preserves in the Fa r East, not only because of the temperature and the humidity but also because salt is usually expensive and scarce and hence low salt concen- trations are commonly used. This offers better conditions for bacterial growth. Furthermore, the salt is often very impure, hygroscopic, and contaminated with many halophile microorganisms, which may influence quality of the final product.
However, by following more or less constant techniques (simple as these may be) over a period of many years, a fairly standardized prodiict
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can be obtained. Alterations in texture, appearance, or flavor caused by microorganisms or by tissue enzymes are kept within uniform bounds. Fish products so treated develop uniform characteristics during ripen- ing, which appeal to consumers accustomed to them.
The present author has found that, when working on certain food products prepared in Java with the aid of certain fungi, the microbial flora in and around the place of manufacture consists mainly of the fungi used. The same is probably true with regard to the bacterial flora in many small plants in the Fa r East, where, over the yeass, fish has been salted and prepared in the same way with ingredients of the same origin.
These interesting methods of fish preservation have originated from the empirical findings of local populations. A limited amount of work on the biological and enzymatic changes in the products have been done mainly in Indochina and Indonesia, publications of which are scarcely known outside this area.
I n the following sections, we shall review a number of the indigenous methods of fish preservation in the Far East. Of those described, many are more or less standardized for a given village or region. However, many minor, o r even major, modifications are used in other places in the same area. A few examples will be given which indicate that these relatively simple methods of fish preservation offer a number of possi- bilities for further research, the results of which should enable the exist- ing cheap methods to be improved. However, the acceptability of the products from the point of view of the rice-eater must always be kept in mind.
Consideration will be given to: (1) fish sauces; (2) fish pastes; ( 3 ) salted fish, not (or partially) dried; (4) dried, or salted and dried, fish products ; and ( 5 ) miscellaneous products. The salted and partially dried fish and the fish sauces have been studied more extensively than have the other products. The rather primitive methods of manufactur- ing fish meal and oil and smoked fish are not discussed because of their limited local importance.
11. FISH SAUCES
A number of fish sauces are well known in Southeast Asia. Some of them are extremely popular in Indochina, scarcely known in Indonesia, and practically unknown in India. A very good review of the literature concerning the investigations of the numerous fish products in Indochina has been given by Westenberg (1941). It seems probable that fish sauces first came into use in regions where the climate is too rainy to
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allow sun-drying of the fish and where sufficient fuel cannot be found for artificial drying.
From a nutritional point of view, fish sauces are not so important nu- tritionally because their salt content is usually high ; this prohibits their consumption in large quantities. They contain mainly hydrolyzed pro- tein and minerals (sodium chloride and calcium salts) ; they therefore are to be compared with soy sauce. They contain sufficient calcium salts to be rather important sources of this mineral if eaten regularly and in sufficient quantity. They are used chiefly as condiments for flavoring rice dishes. Because they are consumed regularly and by a great part of the population in countries such as Indochina and Thailand, the fish sauce industry is a very important one.
Microbiological and other processes play an important role in the preparation of many fish products such as the pastes and undried salted products, but their most pronounced effects are noted in the fish sauces. One of these sauces, nuoc mam, has been carefully studied by a number of investigators, and many of the findings concerning nuoc mam may be applicable, to a certain extent, to other fish products of Southeast Asia.
The nuoc mam produced in Indochina is consumed almost entirely by the inland trade, although exports formerly were made to Thailand and Malaya. It is not easy to determine the total annual production, but estimates range from 35,000 to 100,000 tons (Gruvel, 1925). I n 1935 about 67,000 tons were produced (Bouvier and Autret, 1944). The economic status of nuoc mam is evident from the amount of salt used. I n the year 1925, in the province of Binh-Thuan, the total salt used was approximately 15,000,000 kg. from which about 40,618,160 1. of nuoc mam were manufactured (Guillerm, 1928). During the World Wars I and 11, nuoc mam was concentrated, canned, and shipped to the Anna- mite troops in France (RosB, 1919b,c ; Bouvier and Autret, 1944).
A short description of the manufacture of nuoc mam will now be given. (It should be remembered that there are numerous modifications; it is not easy to say which one is the best.) Nuoc mam is a clear, brown liquid, rich in salt and soluble nitrogen compounds. It has a peculiar flavor. It is produced along the coasts of Indochina and Thailand (RosB, 1918, 1919 ; BrBmond, 1919 ; Mesnard and RosB, 1920 ; Gruvel, 1925 ; Guillerm, 1928). The most important production centers in Indo- china are in the province of Binh-Thuan (South Annam) and on the island of PhuQuoc. The best products have a rather strong, cheese-like odor and a salty taste. The cheaper products are unattractive and gen- erally not liked by the Westerner. Nuoc mam is usually prepared from different kinds of small sea fish, mainly species of Clupeidae and Caran-
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gidae : Decapterus, Engradis, Dorosoma, Clupeodes, Xtolephorus, and others. However, since World War 11, nuoc mam has been produced increasingly from fresh-water fish.
I n the most primitive method of manufacture, small fish are first kneaded and pressed by hand. They are then salted and placed in earthenware pots, which are then tightly sealed and buried in the ground. They are left there for several months. When dug up and opened, the supernatant liquid that has been formed is carefully decanted. This liquor is the nuoc mam.
I n the commercial manufacture of nuoc mam in South Annam, large vats, with a bamboo tap fitted near the bottom, are used (RosB, 1918a; Gruvel, 1925). On the inside of the vat the tap stem is buried under shells, sometimes mixed with rice. The inner opening contains a plug of hair in order to improve the filtering power of the shell layer.
The fresh, uncleaned fish are mixed with salt and dumped into the vats. The amount of salt varies according to the kind of fish; usually four to five parts of salt to six parts of fish are used (RosB, 1918a). For some species of fish proportionally more salt is added to the upper layers in the vat. The fish are piled above the top of the vat. A final layer of salt is placed on the pile of fish. After 3 days, the collected liquid (called nuoc-boi), which is turbid and bloody in appearance, is drained off. A part of i t is returned to the vat; another portion is saved and used later. On exposure of the liquid to the air, the red color soon vanishes ; the liquid also becomes somewhat clearer (Guillerm, 1930). Meanwhile, the fish have settl...