Preventive method of color deterioration of yellowtail dark muscle during frozen storage and post thawing

ABSTRACT:   The aim of this study was to develop a practical preventive method for color deterioration of sliced or filleted yellowtail muscle, especially of dark muscle, during frozen storage and post thawing. When the sliced meats were packaged in a vacuum with low oxygen permeable flexible films and then stored frozen below −40°C, no significant discoloration or browning of dark muscle was observed for 9 months or more. For higher temperature storage at −20°C or −30°C, nitrogen gas substituted packaging was a useful practical method for storing sliced meats for 6 weeks. In order to prevent color deterioration of sliced meats after thawing and subsequent storage at 0°C, the efficacy of materials of packaging was investigated. The most desirable result was obtained by using a film with oxygen permeability of 50–90 cm³/m² per 24 h.     

Lipid peroxidation-derived hepatotoxic aldehydes, 4-hydroxy-2E-hexenal in smoked fish meat products

ABSTRACT:   Contents of 4-hydroxy-2 E -hexenal (HHE), hepatotoxic aldehydes, in smoked fish meat products (smoked salmon and fish meat sausage) were analyzed. Large differences in these contents between the different samples were observed. Very low levels of HHE were detected in fish meat sausage samples. However, a high level of HHE was observed in one batch of smoked salmon. Changes of HHE contents in yellowtail meat containing cherry and sugi wood vinegar stored at 0°C were also analyzed for 7 days. Malonaldehyde (MA) was also analyzed in these samples as an index of the lipid peroxidation level. After 3 or 7 days of storage, HHE contents in both wood vinegar-added samples were significantly higher, but MA contents were significantly lower than those of the control.     

Effects of temperature, salinity and irradiance on the growth of the toxic dinoflagellate Gymnodinium catenatum (Dinophyceae) isolated from Hiroshima Bay, Japan

ABSTRACT: Temperature and salinity ranges in which Gymnodinium catenatum (Hiroshima Bay strain) showed specific growth rates higher than 0.2/day were approximately 20–30°C and 20–32. The specific growth rate (μ), expressed as a polynomial equation as functions of temperature ( T ; °C) and salinity ( S ) were μ = (−6.84 × 10⁻⁴ T ² + 0.0354 T – 0.213) × (−1.03 × 10⁻³ S ² + 0.0579 S – 0.548)/0.31; the maximum growth rate (0.31/day) was obtained at 25°C and 30. From a comparison with field data recording temperature, salinity and light intensity, this species may be expected to bloom from summer to autumn in Hiroshima Bay.     

Effect of vacuum treatment on smoke penetration into boiled skipjack loins for production of smoke-dried skipjack

ABSTRACT: The present work evaluates the effect of vacuum treatment on smoke penetration into boiled skipjack loins for the production of smoke-dried skipjack. Using a vacuum freeze-dryer, the boiled skipjack loins were vacuumed immediately after being boiled at a pressure of 400 Pa for 30 min in order to reduce the lipid and water contents. The vacuumed boiled meats were then smoked and dried at 90 ± 10°C for 3 h a day for 6 days in a metal kiln (internal diameter 24 cm × 24 cm × 70 cm height), using an electric heater (1.2 kW) to heat and generate smoke from cherry tree wood chips. Also, non-vacuumed boiled meats were smoked in the same manner as a control. The vacuum treatment reduced the lipid and water contents by as much as 0.6% and 2.7% on the wet weight basis, respectively. Histological observations showed many clearances among the muscle fibers of the vacuumed boiled meats. The content of phenols that had penetrated the vacuumed boiled meats during the smoke drying procedure was significantly larger ( P < 0.05) than that of the non-vacuumed boiled meats. Accordingly, the vacuum treatment accelerated the penetration of phenols into the boiled meats and enhanced the function of antioxidant substances, which improved the quality of the smoke-dried skipjack.     

Characterization of 38 kDa and 42 kDa chitinase isozymes from the liver of Japanese common squid Todarodes pacificus

ABSTRACT: Characterization was investigated on the 38 kDa and 42 kDa chitinase (EC3.2.1.14) isozymes from the liver of Japanese common squid Todarodes pacificus . Optimum pH toward colloidal chitin was observed at pH 3.0 for the 38 kDa chitinase, and pH 3.0 and 9.0 for the 42 kDa chitinase. K _m and k _cat of the 38 kDa and 42 kDa chitinases toward a longer substrate, glycol chitin, were 0.071 mg/mL and 1.22/s, and 0.074 mg/mL and 0.196/s, respectively. Alternatively, strong substrate inhibition of both chitinases were observed toward a short substrate, N -acetylchitopentaose (GlcNAc₅). Both chitinases decomposed not only chitin but also chitosan (D. A. 95%). The cleavage pattern and reaction rate were investigated using N -acetylchitooligosaccharides (GlcNAc_n, n  = 2–6). Both chitinases hydrolyzed GlcNAc_n ( n  = 4,5, and 6). The release of GlcNAc was not observed. The speed of the reaction was observed to be in the following order: GlcNAc₄ > GlcNAc₅ > GlcNAc₆ for the 38 kDa chitinase, and GlcNAc₆ > GlcNAc₅ > GlcNAc₄ for the 42 kDa chitinase. Both the chitinases released p -nitrophenol from p -nitrophenyl GlcNAc_n ( n  = 2, 3, and 4). N-terminal amino acid sequences of the 38 kDa and 42 kDa chitinases were YLLSXYFTNWSQYRPGAGKYFPQNI and EYRKVXYYTNWSQYREVPAKFFPEN, respectively.     

Migration pattern of shirauo Salangichthys microdon Bleeker, in the Ishikari River system and adjacent nearshore sea area, Japan, as estimated by otolith microchemistry analysis

ABSTRACT:   The purpose of the present paper was to reveal the migration pattern of shirauo Salangichthys microdon Bleeker, in the Ishikari River system and its adjacent coastal sea areas. To this end, the strontium–calcium (Sr:Ca) ratios of the otoliths of 98 individuals were examined. Profiles of the Sr:Ca ratios during the life history after hatching in the estuary of the Ishikari River fell into two different patterns. One was characterized by a high (slightly fluctuating) Sr:Ca ratio throughout the life history; the other was characterized by an initial high Sr:Ca ratio followed by a lower value later in life. The former pattern was considered to be that of estuary–sea residents and the latter that of upstream migrants. Most upstream migrants migrated upstream once, although several did it twice. Back-calculated body lengths during the upstream and seaward migrations of the upstream migrants varied widely from 6.4 mm to 39.8 mm and from 13.5 mm to 79.4 mm, respectively. These findings suggest that estuary–sea residents and upstream migrants co-occurred spatiotemporally, and suggest a wide variation in migration patterns in the shirauo's life history.     

Toxicity of heavy fuel oil, dispersant, and oil-dispersant mixtures to a marine fish, Pagrus major

ABSTRACT:   This study examines the toxicity of three dispersants and heavy fuel oil to a marine fish, red sea bream ( Pagrus major ). Also studied was the toxicity of a mixture of heavy fuel oil and the least toxic of the three dispersants. The 24-h LC50 of all three dispersants were at least 1500 mg/L; these dispersants appeared relatively less toxic to marine fish than others studied in the past. The mean lethal oil concentration of the water-accommodated oil fraction was 325 µg/L. Mixtures of oil and dispersant were more toxic than dispersant or oil alone. Large amounts of dispersant decreased the toxicity of the mixture for the marine fish. Use of a dispersant-to-oil percentage of 20%, which is recommended by the manufacturer because of its efficiency in oil emulsification and dispersion, yielded higher 24-h oil concentrations and resulted in a higher mortality rate than did the use of higher percentages of dispersant. The application of dispersant to oil in coastal areas, especially with higher activities of fisheries and aquaculture like Japan, must be considered carefully in the context of the benefits versus environmental cost.     

Partial or Total Hemipelvectomy in the Management of Sarcomas in Nine Dogs and Two Cats

The functional results of partial or total hemipelvectomy in seven dogs and two cats with sarcomas involving the pelvis were excellent, and the cosmetic outcome was acceptable to all owners. Tumors in two dogs were inoperable. Locally recurrent cancer occurred in two animals and metastases occurred in three animals. Three dogs survived longer than 2.5 years and the overall and disease-free survival at 12 months was 62%. It appears that osteosarcoma of the pelvis is at least as aggressive as osteosarcoma of limbs and, unless effective adjuvant therapy is used, poorer survival results are likely in dogs with osteosarcoma than with other sarcomas of the pelvis. Hemipelvectomy is an aggressive surgical procedure that can be used successfully in selected dogs and cats with cancer involving the pelvis.     

Effect of different photoperiod cycles on metabolic rate and energy loss of fed and unfed adult tilapia Oreochromis niloticus: Part II

ABSTRACT: To study the influence of different photoperiod cycles on the metabolic rate and energy loss of fed and unfed adult tilapia Oreochromis niloticus (bodyweight 102–107 g) at 28°C, four photoperiod cycles (i.e. 3L : 3D, 6L : 6D, 12L : 12D, and 24L : 24D) were applied. A computer-operated respirometer with a closed tank was used so as to prevent water from condensing from the air or evaporating into the air. A photoperiod-mediated metabolic cycle was demonstrated during the routine state in which the metabolic rate was higher during the light phase compared with during the dark phase for all photoperiods. The combined effects of photoperiod and feeding episodes acted as a strong Zeitgeber (cue or synchronizer) for synchronizing the daily rhythm in fed fish. Fish exposed to short photoperiod cycles showed a higher metabolic rate and energy loss compared with those exposed to longer photoperiod cycles. Mean oxygen consumption in the fed and unfed fish were 295.7 mg/kg per h and 149.8 mg/kg per h, respectively, during the 3L : 3D period; 286.5 mg/kg per h and 143.3 mg/kg per h during the 6L : 6D period; 262.2 mg/kg per h and 130.3 mg/kg per h during the 12L : 12D period; and 238.3 mg/kg per h and 120.4 mg/kg per h during the 24L : 24D period. The highest post-prandial increase in energy loss was recorded during the 3L : 3D period (56.2 kJ/kg per day), followed by 55.1 kJ/kg per day during the 6L : 6D period, 50.7 kJ/kg per day during the 12L : 12D period, and 45.4 kJ/kg per day during the 24L : 24D period. The study's results demonstrated that the fish conserve energy when raised under longer photoperiod cycles.