Seasonal variation in the chemical composition and microbiological condition of Mediterranean horse mackerel (Trachurus mediterraneus) muscle from the North Aegean Sea (Greece)

The aim of this work was to determine the chemical composition and microbiological quality of Mediterranean horse mackerel (Trachurus mediterraneus) muscle during the year and the consequent advantages or disadvantages in processing the raw material. A total of 180 samples were examined (15 samples per month) during two years (November 2001–November 2003). Fish were caught in the coastal waters of Chalkidiki peninsula (Northern Greece). Proximate composition of the muscle during the year resulted in: water 76.8 ± 1.39%, proteins 20.3 ± 0.68%, fat 1.3 ± 1.08% and ash 1.5 ± 0.08%. In March, April and May an increase in fat content of the muscle (2.5%, 2.8% and 2.1%, respectively) and a decrease in water content of the muscle (below 75.9%) were observed. On the contrary, fat content showed a decrease in September and October (0.4% and 0.6%, respectively), while water content of the muscle increased during these months (78.2% and 77.6%, respectively). The protein content of the muscle remained at high values, while the ash content was almost constant during the year. The mean value of muscle pH was 6.38 ± 0.16; extreme values (<6 or >7) of muscle pH were not observed. Total Viable Bacteria, Shewanella putrefaciens and Pseudomonas spp. were used as microbial indices to evaluate the microbiological quality of the muscle. Mean counts of Total Viable Bacteria, S. putrefaciens and Pseudomonas spp. during the year were: 4.01 ± 0.38 log₁₀ cfu/g, 2.37 ± 0.43 log₁₀ cfu/g and 3.34 ± 0.27 log₁₀ cfu/g, respectively. The variations of the values within seasons are minimal and significant homogeneity in the chemical composition and microbiological quality of Mediterranean horse mackerel muscle is observed. This is an important advantage in processing of the raw material.