Lipid and protein changes during the ensilage of blue whiting (Micromesistius poutassou Risso) by acid and biological methods

Fish waste is a potential source of protein for animal nutrition. Ensilage could provide an advantageous means of upgrading these residues. Careful control of the degree of proteolysis and lipid oxidation is required to produce silages of high nutritional value. This paper studies the changes in lipids and protein during storage (15 days) of acid silages (with 0, 0.25 and 0.43%, w/w, of formaldehyde) and biological silages (with 10 and 20% molasses or dehydrated whey) prepared from blue whiting. A remarkable reduction in protein solubilisation values was achieved by adding formaldehyde. However, formaldehyde addition led to an increase in the peroxide value of the oil extracted from the silages. Ensiling by biological methods seems promising. It yielded both a considerable reduction in protein solubilisation and in basic volatile nitrogen when compared with acid ensilage. In addition, the oil from biological silages had lower peroxide values than the oil from acid silages with added formaldehyde.