Quantitative changes in bacteria, amino acids and biogenic amines in sardine (<i>Sardina pilchardus</i>) stored at ambient temperature (25–28°C) and in ice

Abstract

Summary Freshly caught sardines contained high levels of bacteria located mainly on the skin and the gills. These bacteria invaded and grew rapidly in sardine muscle, reaching 5x10 8 c.f.u. g ‐1 and 6x10 8 c.f.u. g ‐1 respectively after 24h at ambient temperature and 8 days in ice. Histidine, arginine, lysine, tyrosine and methionine levels decreased during storage. The other amino acids, except proline and taurine, accumulated in the fish muscle, indicating an extensive proteolysis. Histamine, cadaverine and putrescine accumulated to levels of 2350ppm, 1050ppm and 300ppm respectively, after 24h storage at ambient temperature. Histamine and cadaverine reached similar levels after 8 days storage in ice, whereas putrescine formation was insignificant. Spermidine and spermine levels increased slightly under ambient conditions. Salting the fish at 8% delayed bacterial and chemical changes but only in iced sardines. The high content of free histidine found in sardines and the susceptibility of its muscle to histamine and cadaverine formation could explain its increasing implication in incidents of histamine poisoning.