19 Fermented Fish Products in the Philippines
Minerva SD. Olympia
In many parts of the world especially in Asia, fermented foods are popular and well liked by the general populace and so widely used that the daily diet of the people would not be complete without them. In a developing country like the Philippines, where many fermented food products are known, their popularity is due not only to their characteristic flavor but also to the fact that other processing methods, such as freezing and canning, are generally expensive.
Despite their popularity, research and development on fermented foods is meager. Most of the traditional food fermentation industries especially in the Philippines are rural, seasonal, labor intensive, informal, and capital deficient. Commonly, fermented foods are sold and consumed in the areas where they are produced.
The methods of processing were developed in homes and improvements were based on the observations of the practitioners. Fermentation processes are normally handed down from generation to generation. There is little interest in knowing the role of microorganisms and the physical and chemical changes that occur in the products. What is recognized are changes in color, odor, and taste that result from modifications of the process or variations in the ingredients or conditions. Most processes are conducted on a trial-and-error basis with little quality control. Product quality primarily depends on the experience of the processor.
In the Philippines, fermented fishery products can be divided into two groups. The first group includes those containing high concentrations of salt - about 15 to 20 percent in the final product. This group consists of bagoong (fish paste) and patis (fish sauce). These products are generally used as condiments.
The second group includes burong isda (fermented rice fish mixture) and burong hipon, also known as balao balao (fermented shrimp rice mixture). These products, when fermented, become acidic with a cheese-like aroma.
FISH PASTE (BAGOONG)
Bagoong is the undigested residue of partially hydrolyzed fish or shrimp. It has a salty and slightly cheese-like odor (Figure 1). The characteristics of this product vary depending on the region where it is made and consumed. In the Tagalog provinces, the fish paste is completely fermented and ground, with or without coloring matter added. In the Ilocos region and Pangasinan provinces, the products are either partially or completely fermented. In the Visayas and Mindanao, the product is slightly fermented without liquid; the fish is hard and solid salt is present (1).
The fish used for bagoong include anchovies, sardines, herring, silverside, shrimp, slipmouth, freshwater porgy, oysters, clams, and other shellfish. The fish are washed thoroughly and drained well. Salt is mixed with the drained samples at varying proportions from 1:3 to 2:7 depending on the bulk of the preparation. The mixture is allowed to ferment for several months or longer until it develops the characteristic flavor and aroma of bagoong.
Bagoong is eaten raw or cooked and is generally used as flavoring or condiment in many traditional recipes. As an appetizer it is sauteed with onions and garlic and served with tomatoes or green mangoes. In rural areas, bagoong is eaten with vegetables, and, especially in the coastal regions, it is often the main source of protein in the diet.
Results of earlier studies on the microbiological changes in bagoong showed that the total viable count decreased with time. Aerobic organisms predominate at the onset of the fermentation followed by the microaerophilic and anaerobic microorganisms at the later stages (2,3). Information gathered on the microflora indicated that both desirable and hazardous microorganisms are present in this product.
FISH SAUCE (PATIS)
In the Philippines the production of fish sauce is always accompanied by the equally important product bagoong. This product is the clear supernatant yellow-brown liquid obtained by decanting and/or pressing or centrifuging bagoong after it has been thoroughly fermented. Fish sauce may be obtained either from fish or shrimp bagoong after I to 2 years of fermentation. The longer the digestion period, the better.
The raw material used is similar to that of the fish paste. They differ only with respect to the period of fermentation. To obtain the fish sauce, the fermentation is continued until liquid forms on top of the mixture, after which it is drained and filtered.
The total bacterial counts decreased rapidly up to the sixth month and declined slightly until the end of fermentation. Most of the organisms isolated were facultative anaerobes.
The solid material is progressively digested with the protein, gradually solubilized by enzyme action, leading to increases in peptides and amino acids in the liquid component. The soluble protein/polypeptide ratio was found to be relatively constant after I month. This suggests that most of the proteolytic activities occurred in the early period. Amino nitrogen and total volatile bases (TVBs) increased steadily until the seventeenth day of fermentation. In addition, the lipids in the fish are believed to be broken down during fermentation to yield fatty acids. These may act as precursors for flavor and aroma compounds and may also participate in the browning reactions that increase with prolonged periods of fermentation.
FERMENTED RICE AND SHRIMP (BALAO BALAO)
Balao balao is a fermented cooked rice and shrimp (Penaeus indicus or Macrobrachium species). The mixture becomes acidic during fermentation, and the shrimp shell reddens and softens. It is commonly prepared for the table in sauteed form and is eaten either as an appetizer or main dish.
The general method for making balao balao is by mixing washed shrimp with salt (about 20 percent w/w)and allowing the mixture to stand for 2 hours or overnight. The shrimp are then drained, mixed with cooled cooked rice, and fermented at room temperature for 7 to 10 days.
The total plate count of this product showed a fluctuating trend. It is believed that this is due to sequencing in the flora involved in the process. Changes in the microflora during fermentation overlap, which suggests that there are changes in conditions during the fermentation that lead to the death of one species and the enhancement of others.
Fermented Fish and Rice (Burong Isda)
This product is a popular traditional food in central Luzon. It is usually prepared using freshwater fish. During fermentation the fish flesh becomes very soft and the bones acquire the characteristic softness of cartilage when cooked. Before serving, it is sauteed in oil, garlic, and onion. Similar to balao balao, it is consumed either as an appetizer or as a main dish.
The method of preparation is almost identical to that for balao balao. The fish is scaled, eviscerated, and filleted. It is mixed with salt and allowed to stand overnight before mixing with cooled cooked rice. Fermentation is also carried out for 7 to 10 days at room temperature.
Sequential changes of the bacterial flora also occur in this product and involve the same lactic acid bacterial group as in balao balao.
During lactic acid fermentation the major chemical change that occurred was the accumulation of lactic acid from the conversion of carbohydrates. This results in changes in the composition and acidity of the product (4). Such changes are attributed to the lactic acid bacteria, which are also referred to as microaerophiles. Changes caused by microaerophiles do not result in the decomposition of the food to its basic components such as CO2, and H2O (5). Instead, the most common end product of their metabolism is lactic acid.
Research and Development
At present, the technological know-how for the improvement of traditional fermented fishing products in the Philippines is not advanced. This holds true in the case of the burong isda process, which will be described in detail.
Burong isda is a traditional fermented fish product in the Philippines. It is similar to naresushi or funasushi of Japan. Previously consumed as condiment (6), it is now often a main dish because of economic conditions. Burong isda is available in two forms, depending on consumer preferences in a particular area. One is called white burong isda, which has a natural product color, and the other is red burong isda, which is colored by the addition of angkak or anka. Angkak or anka is a culture of Monascus purpeveus grown on rice. The former is preferred in the western provinces of the central Luzon, whereas the latter is preferred in the eastern provinces.
There are several kinds of burong isda sold in the market, each named for the kind of fish used. One example is burong dalag, a fermented rice-fish mixture using mudfish, Ophicephalus striatus. Other kinds are shown in Table 1. Our particular study deals with burong bangus, a fermented rice-fish product using milkfish, Chanos chanos, or loangus in the vernacular. The method of preparation is shown in Figure 1.
TABLE 1 Lactic Fermented Fish Products in the Philippines; Varieties of Burong Isda
Microbiological analysis of the fermenting mixture showed a sequential type of fermentation with overlapping growth of lactic acid bacteria. The same pattern was also observed by previous workers on other types of burong isda (8-10) and in balao balao (4, 11). This pattern was not, however, observed in market samples. Instead, only one group of lactic acid bacteria predominated in the product from the onset of the process until it was sold in the market. Market samples were also analyzed for the presence of microorganisms of public health significance. Results showed the presence of coliforms Salmonella, and S. aureus.The same results were also obtained by Ferrer (12).
ISOLATING STARCH-HYDROLYZING LACTIC ACID BACTERIA
During our study on the microorganisms involved in the fermentation of burong bangus, some isolates were found to be capable of hydrolyzing starch (10, 13). Relatively few lactic acid bacteria are known to be starch hydrolyzers, and they were mostly isolated from substrates other than fish. In fact, Bergey's Manual of Determinative Bacteriology (14) does not describe lactobacilli as a starch-hydrolyzing bacteria. However, some of the lactic acid bacteria isolated from burong bangus showed otherwise.
The presence of starch-hydrolyzing lactic acid bacteria was also observed in market samples. One of the starch-hydrolyzing isolates, coded L137, was noted to be present in almost all stages of the fermentation process. It was of interest to investigate how the ability of L137 to utilize starch related to its range and level of amylolytic enzyme activity and the type of enzyme(s) that it produces. L137 was characterized and tentatively identified. The enzyme that it produces was also purified. Tentative identification of L137 showed that this strain possesses characteristics similar to L. plantarum and L. corneyformis subsp. corneyformis. L137, however, differs from these two strains in its ability to utilize starch (15). Earlier studies on the lactic acid fermentation of starch-based products reported that lactic acid bacteria cannot hydrolyze starch. The nonacidformers that predominate in the microflora at the onset of the fermentation process, most of which are amylase producers, first hydrolyze the starch to make it available for lactic acid bacteria (16). However, in some burong bangus samples no nonacidformers were present; yet fermentation went on. The presence of a starch-hydrolyzing lactic acid bacteria in the fermenting rice-fish mixture, especially during the early stages of the process, will ensure a continuous production of metabolizable sugars for subsequent formation of lactic acid. This will result in a rapid decrease of the pH, thereby inhibiting the growth of other microorganisms that may be amylolytic but that might be possible spoilers and/or human health hazards.
Study of the fermenting samples showed appreciable dextrinizing activity. This would indicate that the sugars formed during the process were mostly oligosaccharides. Our study also showed that acidity increases as the fermentation progresses, even with decreasing reducing sugar production. This would mean that the breakdown products of the starch for lactic acid production were oligosaccharides and reducing sugars. The result also indicates that the lactic acid bacteria involved in the fermentation can utilize oligosaccharides to produce lactic acid. Considering the industrial importance of this strain, the enzyme produced by L137 was purified. Results of the study showed that this enzyme indeed produces oligosaccharides when allowed to react with amylose (15). The activity of this enzyme was found to be highly stable at pH 4 to 5 and is optimum at around pH 4.
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