1 Biological Aspects & Chemical Composition of Fish Quality and Safety Issues in Fish Handling A course in quality and safety management in fishery harbours in Sri Lanka - building for better - NARA, DFAR, ICEIDA and UNU-FTP Icelandic International Development Agency (ICEIDA) Iceland United Nations University Fisheries Training Programme (UNU-FTP) Iceland National Aquatic Resources Research and Development Agency (NARA) Sri Lanka Department of Fisheries and Aquatic Resources (DFAR) Sri Lanka

2 Content Biological aspects Anatomy and physiology Chemical composition

3 Learning objectives After this lecture participants will be familiar with: biological aspects, anatomy and physiology chemical composition and factor affecting composition of fish.

4 BIOLOGICAL ASPECTS Classification A quatic vertebrates Use gills to obtain oxygen Have fins Vertebrate classes Sharks and rays Bony fish – Generally important and widely distributed Scientific grouping Biological characteristics Technological characteristicsExamples Cyclostomesjawless fish lampreys, slime-eels Chondrichthyescartilaginous fishhigh urea content in musclesharks, skate, rays Teleostei or bony fish pelagic fish fatty fish (store lipids in body tissue) herring, mackerel, sardine tuna, sprat demersal fish lean (white) fish (store lipids in liver only) grouper, skates, ray fish

5 Anatomy

6 Shape of fish The skeleton Muscle anatomy and function Skin Cardiovascular system Biological aspects of fish related to quality

7 The shape of fish There are basically two shapes of fish: round fish and flat fish. The physical shape of a fish can also be a problem for spoilage since spoilage bacteria grow extensively on the surface of fish. Generally, fish that have a high surface to weight ratio, the rate of deterioration may also increase.

8 Fish have a vertebral column and a cranium covering the brain. In the trunk region they have lateral processes that bear ribs. There is also a corresponding number of false ribs or pin bones. Pin bones cause a great deal of trouble when fish are being filleted or processed. The skeleton of fish (Huss, 1995)

9 Muscle anatomy Most fish muscle tissue is white Many fish have a certain amount of dark tissue The proportion of dark to light muscle varies with the activity of the fish. (Huss, 1995)

10 Dark and white muscles There are many differences in the chemical composition of the white muscle and dark muscle White muscle has more protein than dark muscle Dark muscle contains more lipid, myoglobin, histidine… Ideally suited for oxidative metabolism Rancidity can be a problem in dark muscle

11 Skin Skin covers the outer surface of the body and protects the muscle. Skin secretes a mucus which makes the fish slippery The mucus has main functions: Help the passage of the fish through the water by reducing friction. Give protection against attacks of bacteria and others microscopic organisms which would otherwise infect the fish.

12 Cardiovascular system 1.The heart pumps blood toward the gills. 2.The blood is aerated in the gills. 3.Arterial blood is dispersed into the capillaries where the transfer of oxygen and nutrients to the surrounding tissue takes place. 4.The nutrients from ingested food are absorbed from the intestines, then transported to the liver and later dispersed in the blood. 5.In the kidneys the blood is purified and waste products are excreted via the urine. 6.Bleeding is an important step to prevent the formation of histamine in fish (Huss, 1995)

13 Water: 70.4 – 71.0 % Protein: ~ 23 % Highly digestible protein, essential amino acids Lipids: 1 – 4.6 % Essential & Omega –3 fatty acids Vitamins A,D, E Minerals Na, K, Ca, P Carbohydrates Non-protein nitrogenous compounds. Enzymes Other Chemical composition of tuna

14 Lipids The lipid content varies considerably in fish, 0,1-30%. Classify fish according to fat content. Lean fish (< 1% fat) e.g cod, haddock. semi-fatty fish (<10%) halibut, barracuda, shark, and tuna. fatty fish (>10%) salmon, herring and mackerel. Essential fatty acids Human body can't produce. Must be consumed through the diet. Linoleic and linolenic acids. Important for cellular health, proper glandular functioning, oxygen transport, circulation, cholesterol protection plus healthy skin, mucous membranes and nerves.

15 Omega 3 fatty acids Very low density lipoprotiens (VLDL) Decrease =>Low density lipoprotiens (LDL) Cholesterol (CL) Excess production of eicosanoids Increase =>High density lipoprotiens (HDL) Prevent=> Coronary heart disease Arthritis Blood pressure Thrombosis Tumor growth Main Compounds => EPA, DHA

16 Factors affecting composition of fish SeasonSpawning (fat content & water) AgeYoung, sexually mature fish SexFemale & male EnvironmentFeed, water temperature Body LocationLight & dark muscles Type of fishSharks and ray fish contain high urea Pelagic & demersal fish

17 Seasonal variation in the chemical composition of (a) herring fillets (Clupea harengus) and (b) mackerel fillets (Scomber scombrus)

18 References Huss, H.H. Quality and quality changes in fresh fish. FAO 348, 1995 Donald R.Swift MSC. Aquaculture training manual, 1985 Ian Dore. Shellfish,1991. R.Kreuzer. Cephalopods: Handling, processing and products. FAO 254, 1984.