• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.1
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• pp.12-17
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• 2014

The cooling of precooked skipjack Katsuwonus pelamis is a critical thermal process in tuna canning because it affects the quality and yield of the canned tuna, as well as productivity. The combined method of vacuum cooling followed by water spraying (VC-WS) was investigated to increase cooling rates, and prevent loss of yield of the precooked tuna during vacuum cooling. For VC-WS, the precooked skipjack was cooled to $30^{\circ}C$ by vacuum at 31 mmHg and then wetted by spraying water for 2 min. The effects of VC-WS on cooling times, cooling loss, color, texture and lipid oxidation of the precooked tuna were compared with conventional spray cooling (SC).The cooling times for precooked skipjack from $75^{\circ}C-30^{\circ}C$ were 11 min for VC-WS and 145 min for SC. The cooling losses were 1.7 % for VC-WS and 1.6 % for SC. Peroxide and thiobarbituric acid (TBA) values of VC-WS were lower than those of SC. The loin of the VC-WS-treated skipjack was brighter and harder than the SC loin, as indicated by higher lightness and hardness values. Based on these results, we believe that the VC-WS process could compensate for the cooling loss of vacuum cooling and minimize changes in quality that occur during cooling of precooked skipjack tuna.

• Proceedings of the Korean Society of Life Science Conference
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• 2001.09a
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• pp.96-96
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• 2001

• 한국해양학회지
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• v.19 no.1
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• pp.1-10
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• 1984

an analysis of stomach contents of skipjack tuna Katsuwonus pelamis and plankton samples collected during troll fishing operations showed that the abundance of some dominant organisms in tuna stomachs was related to their abundance in the plankton. Fish larvae mainly pilchards, Nyctiphanes australis, brachyuran and other decapod larvae and calanoid copepods are important food item for skipjack. The copepods Undinula vulgaris and Nannocalanus minor occurred consistently throughout the survey period in both stomach contents and plankton samples. U. vulgaris appeared to be a preferred food considering its high percentage composition in tuna stomachs compared with its low percentage composition in the plankton. Temora turbinata and N. minor may also serve as important food items for skipjack. The largest catches of the fish were made in January and February when plankton organisms were composed dominantly of N. australis, copepods and brachyuran larvae. The main stomach contents during this period were N. australis and brachyuran larvae.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.4
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• pp.430-436
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• 2003

This paper describes the relationship between the distribution of tuna and ENSO events in the Pacific Ocean which have occurred on a regular basis of 3-5 year terms. Annual catches and catch ratios of skipjack Funa, Katswonus pelamis and yellowfin tuna, Thunnus albacares largely increased during El $Ni\~{n}o$ years, while it decreased during La $Ni\~{n}a$ years. However, the effect of El $Ni\~{n}o$ on the distribution of tuna seemed to be more significant to yellowfin tuna which usually occurr the upper thermocline depth increases due to the elevated thermocline in the Western and Central Pacific Ocean.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.5
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• pp.467-472
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• 2017

There is increasing interest in developing flavor-enriched concentrate using byproducts of skipjack tuna Ktsuwonus pelamis as a replacement for commercial beef bone extract concentrate (CBB-EC). This study was compared on sanitary and nutritional characteristics between skipjack tuna frame extract concentrate (ST-EC) and CBB-EC as a control of skipjack tuna frame extract concentrate. The moisture contents of CBB-EC and ST-EC 41.4-4.9% and 45.3%, respectively. The results of viable cell counts and E. coli assays suggested that CBB-EC and ST-EC is a safe and sanitary for use in food. There were no differences in peroxide values among CBB-ECs. The total amino acid contents in CBB-EC and ST-EC were 25.6-29.3 g/100 g and 37.9 g/100 g, respectively, and the major amino acids present glutamic acid, proline, glycine, alanine and arginine. Regardless of kinds of the mineral, mineral contents of ST-EC higher than those of CBB-EC. The major fatty acids were 16:0, 18:0 and 18:1n-9 in CBB-EC, 16:0, 18:1n-9 and 22:6n-3 in ST-EC. These results can be used as background information to develop flavor-enriched concentrates from byproducts of skipjack tuna as replacement for CBB-EC.

• Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.305-310
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• 2009

This study was carried out to evaluate the use of fermented skipjack tuna viscera (FSTV) as an alternative for fish meal in juvenile olive flounder (Paralichthys olivaceus) diets. Lactobacillus bulgaricus was used as a starter for fermentation of skipjack tuna viscera. Four isonitrogenous (49% crude protein) and isocaloric (4 kcal/g DM) diets were formulated to contain graded levels (0, 5, 10, and 15%) of FSTV. Each experimental diet was fed three replicate groups (40 fish per tank) of juvenile flounder (average weight, $3.3\pm0.2$ g) for 5 weeks. At the end of feeding experiment, inclusion of FSTV up to 15% in diets did not affect survival rate (%) and weight gain of fish. Feed efficiency, protein efficiency ratio, protein and lipid retentions of fish fed the diet containing 10% FSTV were higher than those of fish fed the control diet (P<0.05). The values of fish fed the diet containing 15% FSTV were not different from those of fish fed other diets. Whole body lipid content of fish fed the diet containing 10% FSTV was higher than that of fish fed the diet containing 15% FSTV and control diet. The present results indicate that fermented skipjack tuna viscera could partially replace fish meal in juvenile flounder feed, and the inclusion of 10% FSTV may be efficient in improving the feed utilization of fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.3
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• pp.264-272
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• 2019

The aim of this study is to analyze the relationship between international oil price as a fuel cost in overseas fisheries and skipjack tuna price as a part of main products in overseas fisheries using monthly time series data from 2008 to 2017. The study also tried to analyze the change of fishing profits by fuel cost. For a time series analysis, this study conducted both the unit-root test for stability of data and the Johansen cointegration test for long-term equilibrium relations among variables. In addition, it used not only the Granger causality test to examine interactions among variables, but also the Vector Auto Regressive (VAR) model to estimate statistical impacts among variables used in the model. Results of this study are as follows. First, each data on variables was not found to be stationary from the ADF unit-root test and long-term equilibrium relations among variables were not found from a Johansen cointegration test. Second, the Granger causality test showed that the international oil prices would directly cause changes in skipjack tuna prices. Third, the VAR model indicated that the posterior t-2 period change of international oil price would have an statistically significant effect on changes of skipjack tuna prices. Finally, fishing profits from skipjack would be decreased by 0.06% if the fuel cost increases by 1%.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.158-163
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• 2000

As a part of investigation for utilizing of canned tuna processing by-products as a food resource, we examined the processing conditions and characteristics (extraction methods and ashing condition) of a calcium powder from skipjack tuna bone. Among ashing, autoclaving, and shaking methods for extraction of calcium powder from skipjack tuna bone, ashing method was superior to other methods on the aspect of fish odor, white index, and calcium recovery of calcium powder. Based on the results of white index and soluble calcium ratio, the optimal ashing temperature and time for preparation of a calcium powder from skipjack tuna bone was at $900{\circ}C for 15 min$. Cohesive ratio of calcium powder by shaking at pH 7.0 was increased up to 16 hrs, but after that almost unchanged. Cohesive ratio of calcium powder by shaking for 24 hrs was increased at neutral and alkaline conditions (pH 6-8 and pH 9-11), but almost unchanged at acidic conditions (pH 2-5). For the effective utilization of the calcium powder from skipjack tuna bone, a suitable treatment is needed for improvement of calcium solubility at neutral condition.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.1
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• pp.1-7
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• 1997

In order to utilize fish by-products from the skipjack tuna (Katsuwonus pelamis) canning manufactures Lactobacillus buigaricus KCTC 3188 and L. piantarum KCTC 1048 were used as a starter culture for the preparation of fermented fish silage with skipjark tuna viscera. The optimum temperature and pH on barterial growth and lactic acid production of L. bulgaricus and L. plantarum in MRS broth were $35^{\circ}C$ and around pH 6.0, respectively. And the optimum concentrations of the carbohydrate sources added to the broths were $7\%$ for dextrose and $10\%$ for molasses on the basis of total weights of skipjack tuna viscera. The pH of acid treated skipjack tuna viscera silage (ASS) slightly increased from 4.0 to 4.5, while that of fermented skipjack tuna viscera silages by the use of lactic acid bacterias (FSS) was significantly declined from 5.9 to about 40 after 42 days of storage at $35^{\circ}C$. Though the content of volatile basie nitrogen (VBN) in ASS was lower than those of FSS after 42 days of storage at $35^{\circ}C$, VBN content in silages slightly increased from an initial value of $62\~65{\cdot}mg/100g$ to final value of $113\~155\;mg/100g$ over 42 days. The fermented silage by L. piantarum reached a maximum concentration of amino nitrogen and showed $81\%$ of hydrolysis degree after 4 days of storage at $35^{\circ}C$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.1
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• pp.8-15
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• 1997

For an effective use of fish by-products from the skipjack tuna (Katsuwonus pelamis) canning manufactures, the changes of chemical properties of skipjark tuna viscera silage by the processing method during storage were investigated. The acid treated skipjack tuna viscera silage (ASS) were higher in the contents of moisture, lipid, protein and mineral but lower in the contents of carbohydrate and polyunsaturated fatty acids than those of fermented skipjack tuna viscera silage (FSS) by L. bulgaricus, KCTC 3188 and L. plantarum, KCTC 1048. Especially, the contents of total n-3 fatty acids in FSS increased remarkably during storage. The dominant amino acids in ASS and FSS were glutamic acid (Glu), aspartic acid (Asp), leucine (Leu), glycine (Gly) and alanine (Ala). And the contents of tryptophan (Trp) decreased by $30\%$ in ASS and $5\%$ in FSS in comparision with that of raw skipjack tuna viscera after 42 days of storage. The concentration of vitamin $B_1\;and\;B_2$ in FSS increased gradually during storage but the concentration of vitamin $B_2$ in ASS decreased. In the organoleptic evaluation, ASS gave a grayish brown color and a fishy odor. On the other hand, FSS had reddish brown color and sour taste by the production of lactic arid during storage.