Fish meal: general concepts
Although there is no aquaculture with the finality of manufacturing fish meal, is is true that fish meal can be a by-product of this industry, at the same timethat is a raw material for the formulation of rations.
Fish meal is a product obtained by molturation and disecation of whole of parts of fish or residues of tinny industries, with or without oil extraction. The usual manufacturing method is started with a grounded and powdered process of the fish and it cooking at 100 ºC during 20 minutes. After this, the products are pressed and centrifuged to extract fish oil. In this process soluble fraction is obteined that can be sold alone (fish solubles) or re-add to meal. The last step is re-drying the fish meal to a maximum moisture level of 10%. In this first steps, an antioxidant to avoid-rancidness of fats and meal combustion.
The nutritive value of fish meal depends on the kind of fish but this value is around 65 % as average. The average ashes percentage is around 16- 20 %. The content of fats can also vary but the average level is 9 %.
On the other hand freshness of product and storage conditions affect the spoilage by microbial or enzymatic activity or rancidness and as a consequence, its content of peroxides, total volatile nitrogen (TVN) or toxic biogenic amines.
High temperatures and long drying times decrease aminoacids availability by formation of Maillard products. Finally solubles recycling alters chemical composition and solubility of the protein of final product. Manufacturing process of the meal, has finally importance on the final nutritive value.
The most important nutritive parameter in fish meal is protein, because of content of highly digestible essential amino acids, that can vary according to the fish meal origin. The most valued amino acids obtained from fish meal are lysine and metionine.
Fish mela is highly digestible. It is important for its content oessential fatty acids of ling chain (>18 C) of the series n-3 that suppose around 1/3 of the total fat content.
Fish meal also apports high content of highly available phosphorus, microminerals (Se, Zn, Cu, Fe and Zn) and B group vitamin (specially choline, biotin, riboflavin and B12).