Temperature influence on the white muscle growth dynamics of the sea bass Dicentrarchus labrax, L. Flesh quality implications at commercial size

Abstract

Rearing temperature was used to monitor muscle growth patterns of sea bass Dicentrarchus labrax, L. from hatching to the commercial size (350 g, 30 cm). At this moment, the white muscle cellularity, proximate composition and organoleptic parameters of the fillet were analysed to evaluate the influence of temperature on the structure and quality of the commercial product. One ambient (A/A) and three warm regimes of temperature were compared. In warmed tanks temperature was raised to 19 °C: during the larval period (W/A), only during the cool seasons (winter and early spring) (A/W), or both during the larval period and cool seasons (W/W). High temperature during the larval period was positive for an advanced yield of fingerlings and early juveniles. Winter heating of juveniles also advanced the time to reach 200 g by 25 days. However, independently of the thermal regime all fish attained the commercial size at approximately 600 days. Temperature modulated the rates of hypertrophy and hyperplasia of white muscle fibres throughout the larval, fingerling and juvenile periods, such that at commercial size the number and size distributions of muscle fibres varied depending on the previous thermal story. Thus, the density of muscle fibres (number/mm2) was maximum in tank W/A (212.19±8.77) and minimum in W/W (151.95±8.7) (p<0.001). The proximate composition varied for moisture and protein content, but independently of temperature, all the sensorial attributes of cooked flesh (firmness, juiciness, fattiness, chewiness, flavour and odour) were similar. Thus, no correlation between muscle fibre size and flesh texture was found. Compensatory growth of fish reared at ambient temperature and the uniformity of the proximate composition and sensorial properties evaluated by panellists minimized the impact of temperature on both the time at harvest and the quality of the commercial product.