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Muscle colour development in Arctic charr, Salvelinus alpinus (L.), monitored by fibre‐optics and electrical impedance
Author(s) -
Swatland H J,
Darkin F,
Naylor S J,
Caston L,
Moccia R D
Publication year - 1998
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1046/j.1365-2109.1998.00211.x
Subject(s) - salvelinus , biology , arctic , zoology , fishery , anatomy , ecology , fish <actinopterygii> , trout
Farmed Arctic charr, Salvelinus alpinus (L.), (n = 2 70) with a wide range of carotenoid muscle pigmentation were produced by feeding astaxanthin at different levels (0‐120 mg kg −1 feed). Steaks were scored subjectively for pigment concentration (dark = high score). Internal reflectance spectra were measured with a relatively non‐destructive 1‐mm‐diameter fibre‐optic probe. Colour scores were only moderately correlated with reflectance (R = 0.66 and P< 0.01, using data at 500, 610 and 520 nm) because the small‐diameter probe had a short light‐path through the tissue and was highly responsive to scattering. However, in fish without astaxanthin in their diet, this sensitivity to microstructural causes of scattering revealed that fibre‐optic reflectance increased (P < 0.01) with age from 400 nm (r = 0.68) to 440 nm (r = 0.40), and from 530 nm (r = 0.30) to 700 nm (r = 0.56). In agreement with these results, colour scores decreased with age (r = ‐0.52; P < 0.001; n = 85), as did electrical resistance 24 h post‐mortem (r = ‐ 0.42 at 120 Hz, r = ‐0.39 at 1 kHz and r = ‐0.54 at 10 kHz; P < 0.001). Resistance was correlated with colour score (r = 0.40 and P < 0.001 for resistance at 10 kHz) and with fibre‐optic reflectance (R = 0.42 and P < 0.01 for resistance at 120 Hz and 1 kHz versus reflectance from 420 to 680 nm). Thus, without astaxanthin in the diet, muscle colour and tissue integrity at 24 h deteriorated with the age of the fish.