Post-Mortem Softening of Fish Muscle During Chilled Storage as Affected by Bleeding

Bleeding caused the delay of muscle softening in yellowtail, horse mackerel, and striped jack, which are pelagic fish. Conversely, bleeding had no influence on the muscle firmness of red sea bream, flatfish, and rudder-fish, which are demersal fish. Transmission electron microscopy showed delay of degradation of pericellular collagen fibrils in bled yellowtail and horse mackerel. Striped jack showed slower weakening of the pericellular connective tissue in a compression test. However, the demersal fish had no structural difference due to bleeding. These results indicate that removal of blood could delay collagen fibril degradation and muscle softening of pelagic fish.     

Direct fractionation of proteins in particle-containing feedstocks by a filter paper pieces-based DEAE-cellulose column chromatography. Rapid, robust and low-cost capturing procedure for protein

Goldfish were classically conditioned to a mixture of two pulse trains differing in both repetition rate and the spectral profile of the pulses. Animals were then tested for generalization to single pulse trains having one or the other spectral profile presented at a variety of repetition rates. Generalization functions of repetition rate were qualitatively similar to those obtained following conditioning to either of the pulse trains alone. Thus, the spectral profile of each pulse type was appropriately associated with the repetition rate at which that pulse type was presented during conditioning. These results indicate that the two concurrent pulse trains making up the conditioning stimuli were analyzed independently, forming two auditory streams. When either of the two pulse trains were presented with a 500 ms onset asynchrony, stream segregation was enhanced. These and other results suggest that many fundamental features of the human sense of hearing are widely shared among vertebrate animals, and may have developed first among fishes.     

Muscle Firmness and Structure of Raw and Cooked Arrow Squid Mantle as Affected by Freshness

Changes in firmness and structure of arrow squid (Loligo bleekert) mantle muscle during refrigeration (5°C) were studied. Shear force of raw mantle decreased sharply between 3 and 9 h refrigeration after killing. Light microscopic observations showed many pores between muscle cells in the softened raw samples. Transmission electron microscopic observations suggested that the spaces appeared as a result of detachment of muscle cells from connective tissues. After cooking the stored raw muscle, the shear force and muscle structure were almost the same for samples with different storage times. Freshness had an influence on raw squid muscle firmness and structure but not on cooked muscle.     

Trial for quality control in mercury contents by using tail muscle of full-cycle cultured bluefin tuna (Thunnus orientalis)

Substantial amounts of mercury are usually present in tuna muscle, with levels in excess of 10 times the standard safety value present in some individuals. Inspection of individual fish for mercury content would be desirable but may not be cost-effective. In this study, we tried to establish a low-cost system for checking the mercury content of tuna by using a tail muscle that is usually discarded. The samples used in this experiment were bluefin tuna, cultured in the Fisheries Laboratory of Kinki University (Oshima Experimental Station, Wakayama, Japan). They were raised from eggs spawned in 2002. Ninety-eight individuals, weighing 22.3 to 61.6 kg, were selected between December 2004 and November 2005. In nine individuals, the mercury content of the tail was compared with that of the whole body. The total mercury level was measured using the reduction vaporizing atomic absorption method after acid digestion. Except for the front of the abdomen, where the mercury content was lower (0.490 ppm), the mercury content of other parts of the fish did not differ from that of the tail muscle (0.631 ppm). Therefore, the overall mercury concentration in bluefin tuna could be estimated to be almost the same and/or lower than that of the tail muscle. On the basis of these results, for 1 year we investigated the quantity of mercury in full-cycle cultured bluefin tuna that were shipped. The mercury concentration showed no increase irrespective of increases of body weight.     

Assessment of concentrations of toxic elements in aquaculture food products in Malaysia

Thirteen species of aquaculture food products, including fresh water and marine fish, prawns, and seaweed were collected from 37 aquaculture farms in Malaysia. Muscle and liver specimens from these species were tested for the presence of As, Cd, Cr, Cu, Hg, Pb, and Zn by using a heat vaporisation atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrophotometer. Sea bass from each collected site were comparatively studied, where As concentrations were assumed to be caused by different culture system; and, Hg and Pb concentration were assumed to be due to anthropogenic activities in specific sites. The calculated estimated intake values of Malaysians for total As, Cd, Cr, Cu, Hg, Pb, and Zn in the muscle of the examined species were 3.713, 0.115, 0.113, 4.268, 0.211, 0.738 and 15.863 μg/kg b.w./day. None of the values exceeded the JECFA guideline values and would pose no health hazards for consumers.     

Changes in Physical/chemical Composition and Histological Properties of Dorsal and Ventral Ordinary Muscles of Full-cycle Cultured Pacific Bluefin Tuna, Thunnus orientalis, During Chilled Storage

Using full‐cycle cultured Pacific bluefin tuna (BW: 33.5 ± 2.7 kg, cultured for about 33 mo), the physical/ chemical composition and histological properties of the cephalal parts of the dorsal ordinary muscles (DOMs) and ventral ordinary muscles (VOMs) were investigated during chilled storage at 4 °C for 69 h. VOM showed high fat content compared with DOM. The breaking strength of DOM increased up to 33 h but decreased thereafter, whereas VOM decreased gradually after 15 h. The pH and glycogen content of DOMs and VOMs decreased gradually after 9 h. The met‐myoglobin (met‐Mb)% and K‐value of DOMs and VOMs increased gradually during storage. Extension of intercellular spaces of DOM was observed by LM during storage. The abundant quantity of glycogen granules that accumulated around the myofibrils of DOM was confirmed by TEM to decrease during storage (especially, from 15 h).     

Changes of proximate and fatty acid compositions of the dorsal and ventral ordinary muscles of the full-cycle cultured Pacific bluefin tuna Thunnus orientalis with the growth

Using the full-cycle cultured (FC) Pacific bluefin tuna, Thunnus orientalis [body weights: 13.1 ± 4.5 (FC1; April in 2004), 20.2 ± 1.8 (FC2; July in 2004), 28.5 ± 6.3 (FC3; November in 2004), 27.0 ± 3.3 (FC4; February in 2005) and 33.5 ± 4.7 kg (FC5; May in 2005), n = 3, respectively] and wild bluefin tuna [33.3 ± 1.5kg (June in 2005), n = 3], proximate and fatty acid compositions of the cephalal (Ce-) and caudal (Ca-) parts of the dorsal (D) and ventral (V) ordinary muscles (OMs) were investigated. Lipid contents of the Ce-DOM and VOMs of FC1-5 increased with growth. In particular, lipid content of the Ce-DOM (23.0%) and VOMs (55.1%) of FC5 was higher (P < 0.05) than those of wild tuna [D-(2.0%) and VOMs (16.2%)]. However, lipid contents of the Ca-DOM and VOMs of FC1-5 did not change with growth. On the other hand, the fatty acid compositions of the Ce-DOM and VOMs of FC2-5 resembled each other. However, there was no specific tendency of the changes of each fatty acid composition of the Ce-DOM of FC tuna with growth. On the other hand, total monounsaturated fatty acid content (30.1%) of the Ce-DOM of FC5 was higher (P < 0.05) than that (25.5%) of wild tuna. The ratio of n–3: n–6 (9.4%) of the Ce-VOM of FC5 was lower (P < 0.05) than that (14.0%) of wild tuna. However, the fatty acid compositions of the Ce-DOM and VOMs of FC tuna were not reflected by those of feed (whole fish bodies of sesame mackerel).     

Interdependence Between Heat Solubility and Pyridinoline Contents of Squid Mantle Collagen

ABSTRACT: A considerable amount of squid mantle collagen, 45% to 70% of total collagen, was not solubilized even after 30 min of heating in boiling water with its fibrous structure left intact. Pyridinoline, one of the major intermo-lecular crosslinks in matured collagen, was more predominantly included in the insoluble collagen than in the soluble one (p < 0.05). These results suggest that pyridinoline is closely related to the heat solubility of squid collagen.     

Structural and ultrastructural changes of full-cycle cultured Pacific bluefin tuna (Thunnus orientalis) muscle slices during chilled storage

Background: This study examined the structural and ultrastructural changes of dorsal and ventral muscle tissues of full‐cycle cultured Pacific bluefin tuna (PBT), Thunnus orientalis Temminck & Schlegel 1844, cut into slices simulating sashimi and placed in chilled storage for varying periods. Structural and ultrastructural changes were determined in order to understand the physical texture by breaking strength measurement. Results: Progressive deterioration of myofibril structure was observed during chilled storage (4 °C) of PBT muscle slices over 5 days post mortem . Muscle degradation included detachment between myofibres, detachment of the plasmalemma, disruption of mitochondria, loss of Z‐line density and alignment, cementation of myofibrils, loss of the hexagonal arrangement of thick versus thin myofilaments and migration of subsarcolemmal nuclei to intermyofibrillar spaces. Conclusion: Loss of myofibre‐myofibre adhesion, detachment of the plasmalemma and disruption of other components did not lower the breaking strength of PBT muscle. This provides evidence that the muscle breaking strength of PBT is not only associated with the detachment of myofibres or detachment of the plasmalemma. Other factors that produce cement‐like substances, such as cementation of the myofibrillar components and degradation of the sarcoplasmic reticulum, may also increase breaking strength. Copyright © 2011 Society of Chemical Industry     

Histological comparison of the dorsal ordinary muscles of wild and full‐cycle cultured Pacific bluefin tuna (Thunnus orientalis)

The histological properties of the cephalad parts of the dorsal ordinary muscles (CD‐OMs) of wild (body weight 33.3 ± 0.9 kg, n = 3) and full‐cycle cultured (body weights 13.1 ± 2.6 (FC 1), 20.2 ± 1.0 (FC 2) and 28.5 ± 3.6 (FC 3) kg, n = 3 respectively) Pacific bluefin tuna were investigated. The CD‐OMs of FC 1–3 tuna showed low moisture content (P < 0.05) and high fat content (about six times more, P < 0.05) in comparison with wild fish. A large quantity of adipose tissue was observed in the wide spaces between muscle fibres in the CD‐OMs of FC 1‐3 tuna. The muscle fibre diameter of the CD‐OM of FC 3 tuna was significantly lower than that of wild fish (P < 0.05). Myofibrils in the CD‐OM of wild tuna were surrounded by a developed sarcoplasmic reticulum and mitochondria; however, there were many glycogen granules among the myofibrils and a large quantity of fat in the CD‐OM of full‐cycle cultured fish. In particular, the glycogen content of the CD‐OM of FC 3 tuna was significantly higher (about 50 times) than that of wild fish. These results indicate that feeding and exercise conditions affect the histological structure and metabolism of the bluefin tuna muscle. Copyright © 2006 Society of Chemical Industry