DFM Sri Lanka literature review - Nutritional value and quality

Most available research has been conducted to analyze the nutritional components of dried fish. Smoked fish, sun-dried fish, salted fish, and jaadihave been analyzed to assess the quality, microbial content, and nutritional content. The water content of several dried fish varieties has been analyzed in Sachithanandan [1]. Small pelagic dried fish varieties such as sprat, white sardinella (Sardinella albella), flying fish, and thilapia are recorded with lower moisture content. The study further identifies dried fish as the cheapest form of concentrated crude fish protein source for low-income groups of people. Crude fat content (ranges from 4-6.5 percent) and ash content are also comparatively higher than in fresh fish. In-depth comparative studies, using proximate analysis [2], have been conducted for a number of dried fish and krill varieties, including sun-dried (local), boiled, sun-dried (imported), and frozen and sun-dried (imported). Dried krill was found to be a high-quality protein, a good source of structural and trace minerals for the prevention of bone loss and iron deficiency, as well as providing high amounts of beneficial fatty acids, with no toxic levels of fluoride [3].

In a study on the quality of fish using traditional processing methods, smoked Catla species have been identified with the highest level of carcinogenic substances compared to Rohu and Nile tilapia [4]. Despite water activity, moisture content and fat content of home-based smoked fish were less than the critical levels of contamination, although containing higher Polycyclic Aromatic Hydrocarbons (PAHs) than the standard levels (12.0 µgKg-1). Therefore, this study proposes improvements in traditional smoking to avoid the adverse effects on consumers. Jayasinghe et al. [5] analyzed the quality differences in jaadi (fermented fish) in the Sri Lankan market. Quality determinants of jaadi identified were species, processing methods and curing steps, state of the raw fish, the proportion of salt and goraka, handling practices, and storage techniques. Processing centres differed according to processing and handling methods [6]. The authors therefore recommended thorough washing, use of proper amounts of salt and fish, and sanitary practices to produce good quality jaadi.

Comparative research on marine and inland dried fish varieties is also available. Goonewardene and Etoh [7] have investigated the keeping quality, salt content, moisture content and bacteriological characteristics of fresh water and marine dried fish varieties. A higher content of calcium, magnesium, and sulphate has been reported in salted marine dried fish, which has lower keeping quality due to the susceptibility to bacterial and fungal attacks. In contrast, such substances are lower in freshwater dried fish, with less bacterial attacks than on marine dried fish. The authors pointed to an extended shelf life for freshwater dried fish compared to marine dried fish, with the latter being able to retain its quality only for 51 days. Moisture content below 30% and salt content up to 30% have been recommended to control the fungal growth on marine dried fish [8]. The most common species of fungus on dried fish has been identified as Aspergillus niger [9]. Research also shows the impact of the defensive exoskeleton of dried shrimp as a favourable condition for parasitic development. Studies have identified other pests that attack dried fish [10]. Beetles invade dried fish during storage and flies (Diptera species) during the curing process. A clean environment, proper waste disposal, use of good quality raw fish, and sealed wastewater outlets are proposed as best practices to reduce pest invasion [11]. In an analysis on the keeping quality of inland dried fish, Sugathapala et al. [12] recommend immediate processing to counter rapid deterioration processes and to extend the shelf life of dried fish because fresh fish is subjected to rapid post-harvest deterioration through microbial reactions. Moreover, they point out that as a low acid food, fresh fish is susceptible to the growth of food poisoning bacteria.

Most dried fish processing centres, particularly on the South coast, neglect quality standards and hygienic practices [13]. Unhygienic raw materials, contamination due to hazards, dust, insect infestation, and low standard practices increase market vulnerability. Thus, the study recommends following prescribed Sri Lanka quality standards to retain quality and food security of the final product. The quality standards include SLS 643: 1984 and SLS 811: 1988, for dried fish and Maldive fish, respectively and other legal instruments including the Food Act No. 26 of 1980. As dried fish is an affordable food for all households, and a shortage of dried fish would entail a negative impact on the consumption of animal-source foods and proteins, Lokuge et al. [14] have emphasized the need for the fisheries sector to focus on strategies favourable to dried fish producers to improve the industry. This would include enhancing the nutritional quality of dried fish. Even though there is a range of studies on the nutritional content and quality of dried fish processed using different methods, and on a number of key varieties, there appear to be noteworthy research gaps. These include the analysis of nutrients among the wide variety of dried fish consumed in Sri Lanka, especially micro-nutrients in dried fish in comparison to other animal protein products in which these micro-nutrients are unavailable, and the benefits or costs of eating dried fish relative to other animal proteins, from a nutrition perspective. There is also a lack of data on the differences in nutrition content of dried fish in respect to how dried fish is prepared in the cuisine of the island.