Fish silage

Several different methods can be used to produce fish silage: 1) adding inorganic or organic acids to lower the pH to a point where it is stable; 2) addition of inorganic or organic acids to lower the pH to a point at which intrinsic enzymes will liquefy (which are normally most active around pH 4 and at temperatures between 35 to 40 o C) the the protein, prior to adding additional acid to stabilize the pH to a level that is suitable for storage); and 3) adding carbohydrates and allow fermentation to occur, so that enough acid is produced to stabilize the silage. Various acid stabilization methods will be described in later sections. The resultant liquefied product can then be screened to remove bones and reduce the ash content. Mold inhibitors are often added to control surface mold growth.

Enzymes present in the fish waste will digest and liquefy the protein associated with the fish waste (Cetinkaya et al., 1995). Organic or inorganic acids can be used lower the pH of the fish silage to a pH that is stable for storage (Cetinkaya et al., 1995). Fish silage was prepared by boiling fishery waste and then adding enzymes to digest the material and then the pH was adjusted by adding acid (Naret, 1996). Acidifying fish silage by adding an equivalent percentage of either H3PO4, formic acid and acetic acid were evaluated, H3PO4 resulted in the lowest pH and lowest NH3-N content in the silage (Jovic et al., 1998). Formic acid resulted in the highest content of NH3-N (Jovic et al., 1998). Formic acid (4%) treated fish silage was found to be superior to acetic or lactic acid preserved silages (Olivo et al., 1998).