Acid fish silages. Effect of preheating and addition of phosphoric and citric acids on the biochemical quality

Abstract

Whole mackerel (Scomber japonicus), without head or spinal bone, were ensiled. In order to observe the preservative effect, two different acid mixtures were used: conventional sulfuric-acetic and phosphoric-citric. To establish the degree of hydrolysis caused by the endogenous enzymes from the fish, enzyme activity was reduced by heating the fish mixture at 60ºC for five minutes, before acid addition. Samples were taken for analysis during 90 days. The pH was stable in all groups throughout the experiment. In the preheated treatment, enzyme activity was lower and the silage more stable, with less percentage of liquid and lower amounts of soluble protein and free amino acids. After 60 days of storage, an increase in total volatile bases was observed in all products, corresponding to the beginning of a decomposition process, probably due to the high temperatures registered during the experiment. It is concluded that the preheated treatment has advantages in comparison to the other treatments, due to the lower hydrolysis which gives lower amounts of soluble protein and free amino acids.