Fish Products and Byproducts Technology

Unit 9 - Fish meal and fish oil

9.7. Fish meal quality
Quality of fish meal related to raw material and conditions of manufacture and storage
The quality of protein in fish that is the make up of amino acids in relation to animal’s requirement and the availability to the animal are high, particularly in the whole fish. the quality of protein in skin, connective tissues and bone is lower; consequently the quality of protein in offal is some what lower than that in whole fish. For example the proportion of the essential amino acids methionine and lysine in the protein in white fish offal is approximately 10% lower than that in the whole oily fish such as anchovy and pilchards.
Raw material should have less than 80mgN/100g
Fish protein is sensitive to heat. So, the available lysine content is considered to evaluate the quality. There should not be more than 80% loss of available lysine content with reference to the raw material
Oxidation: Oxidative rancidity mainly affects the quality of fish meal. Addition of an antioxidant such ethoxyquin at 700ppm is desirable for oily species. Natural antioxidants such as α-tocopherol also used in order to retard the oxidation process.
Salmonella: The end product should be free from salmonella contamination. Salmonella should never be detected in fish meal. The contaminated lots must be disinfected for example in special apparatus in which the meal is heated at about 90oC with live steam for 10-15 min. Alternatively biocides such as formic acid and propionic acid can be used to treat infected fish meal.
Colour: Fish meal is brown powder. A very dark brown colour especially if accompanied by an aerid “scorched” smell may be the result of over heating.
Particle size: The general practice for meals to have less than 10% that will pass through a1mm sieve and more than 90% passing through a 10 mm sieve.