Post mortem changes and spoilage in rock lobster muscle

Abstract

In an attempt to elucidate the pattern of spoilage in rock lobster (Jmu novae-hollandiae), sarnples of abdominal musculature consisting of flexor, extensor and enveloping muscles were subjected to two treatments; half the musculature, after bisecting along the mediosaggital plane, was immersed for 4 min in 3% sodium chloride solution (untreated) and the other half in 3% sodium chloride containing 15 ppm oxytetracycline (treated). After being drained, the muscles from different lobsters were stored under nitrogen, some at 20°C or 15°C for 72 hr, and some at 0°C for 216 hr.In the untreated samples stored at 20°C or 15°C the concentration of total volatile bases (TVB) and trimethylamine (TMA) rose sharply after 24 hr storage. In both the untreated and treated samples at 0°C for up to 168 hr post mortem and in treated samples at 15°C for up to 56 hr post mortem TVB concentrations remained well below 30 mg ~/ 1 0 0 g muscle. The TMA concentrations did not rise above 5 mg ~/ l 0 0 g muscle during the entire experimental period in samples held at 0°C.The increase in total bacterial counts correlated well with the rise in the concentrations of TVB and TMA in the untreated samples.Changes in the concentrations of free amino acids showed that bacterial breakdown of arginine into ornithine and ammonia accounted for a very high proportion of ammonia present in the TVB.The significance of these observations to rock lobster spoilage is discussed.

The influence of defined ante-mortem stressors on the early post-mortem biochemical processes in the abdominal muscle of the Norway lobster,Nephrops norvegicus(Linnaeus, 1758)

“…Not only is the post-mortem biochemistry of these muscles changed, but consequently the overall quality, palatability and shelf life (use by date) of the meat is altered (Hendricks 1965;Fraser et al 1966;Lee et al 1976; Lewis et al 1981;Sikorski et al 1990;Lowe et al 1993;Sigholt et al 1997;Abdalla et al 1999;Diouf & Rioux 1999). There are numerous studies on spoilage and storage effects in the muscles of crustaceans (Sidhu et al 1974;Stroud et al 1982;Ashie et al 1996;Chinivasagam et al 1996;Shimada et al 2000;Mendes et al 2001;Aubourg et al 2007), but there is very little knowledge of the way in which ante-mortem stressors change the post-mortem biochemistry, and hence quality of related shellfisheries products.…”