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).     

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     

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).     

Enzymatic extraction of oil from yellowfin tuna (Thunnus albacares) by‐products: a comparison with other extraction methods

This study evaluated the quality of oil extracted from yellowfin tuna (Thunnus albacares) by enzymatic hydrolysis (EHO) compared with oil extracted by traditional methods, such as the physical method of cooking and pressing after fishmeal production and the chemical solvent method. The oil extracted by EHO presented the lowest acidity (1.96% oleic acid) and peroxide indexes (5.14 mEq O₂ kg^?1 of oil) and the highest levels of eicosapentaenoic acid (6.05g 100 g^?1) and docosahexaenoic acid (27.15 g 100 g^?1), two omega‐3 fatty acids with high nutritional value. Importantly, oil extraction from yellowfin tuna heads using EHO produced oil rich in omega‐3s with no oxidation. This study shows that this extraction method greatly increases the value of fish by‐products and increases the competitiveness of the fishing industry.     

Fatty acid profile and proximate composition of Pacific mullet (Mugil so‐iuy) caught in the Black Sea

This study demonstrates proximate composition and fatty acid profile of Pacific mullet caught in Turkey. The highest moisture and protein contents were observed with muscle tissues as 83.74 and 10.52%, while the highest fat and ash contents were attributed to female gonads as 11.80 and 0.94%, respectively, with a significant variation amongst months (P < 0.05). Significant variation (P < 0.05) usually occurred amongst months within the same sex for total saturated fatty acids ( ∑ SFA), monosaturated fatty acids ( ∑ MUFA), polyunsaturated fatty acids ( ∑ PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in muscle, although overall mean values between sexes were not found significant. Except for EPA, no variation observed for gonads while significant changes occurred (P < 0.05) with liver samples amongst months. Overall total values of ∑ SFA, ∑ MUFA, ∑ PUFA, DHA and EPA in muscle samples were 29.59, 29.26, 18.06 and 4.48%, respectively, while in gonads ranged as 30.26–33.23%, 35.17–37.47%, 11.87–14.88%, 4.38–5.34% and 3.02–5.02%. These FAs were 21.57–33.11%, 32.89–50.96%, 14.78–20.08%, 0.89–9.94% and 5.85–9.54% for liver, respectively. The results of this study showed that muscle and gonads of Pacific mullet were rich in n‐3 PUFA, especially, EPA, DHA, increasing the value of this species for human consumption.     

Essential oil composition and antibacterial activity of the grapefruit (Citrus Paradisi. L) peel essential oils obtained by solvent‐free microwave extraction: comparison with hydrodistillation

The chemical composition of the essential oil (EO) obtained by solvent‐free microwave extraction (SFME) and hydrodistillation (HD) from the peel of grapefruit (Citrus Paradisi. L) was analysed by gas chromatography/mass spectrometry (GC/MS). Totally, twenty‐five components were identified in the EO. Limonene was observed as dominant (91.5–88.6%) for two extraction methods, SFME and HD, respectively. β‐Pinene (0.8–1.2%), linalool (1.1–0.7%), α‐terpinene (0.7–1.0%) and the other minor components were also detected. Disc diffusion method was applied to determine the antibacterial properties of the EO. The results showed that the EO of grapefruit peel had a wide spectrum of antimicrobial activities against Staphylococcus aureus, Enterococcus faecalis, Staphylococcus epidermidis, Escherichia coli, Salmonella typhimurium, Serratia marcescens and Proteus vulgaris, with their inhibition zones ranging from 11 to 53 mm.