• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.5
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• pp.85-96
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• 2001

This paper describes saturation attacks on reduced-round versions of SKIPJACK. To begin with, we will show how to construct a 16-round distinguisher which distinguishes 16 rounds of SKIPJACK from a random permutation. The distinguisher is used to attack on 18(5~22) and 23(5~27) rounds of SKIPJACK. We can also construct a 20-around distinguisher based on the 16-round distinguisher. This distinguisher is used to attack on 22(1~22) and 27(1~27) rounds of SKIPJACK. The 80-bit user key of 27 rounds of SKIPJACK can be recovered with $2^{50}$ chosen plaintexts and 3\cdot 2^{75}$ encryption times.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.2
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• pp.77-84
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• 2004

The powder and liquid products of seasoned and smoked skipjack tuna (Euthynus pelamis) was manufactured by using small skipjack tuna (1-2 kg, 20-30 cm) captured in the East Sea, Korea. Smoking was done three times at $80^{\circ}C$ for 8 hrs to decrease the moisture content below $15\%.$ The seasoned and smoked skipjack tuna powder with liquid smoke showed the lower pH than the control. The pH, VBN, amino nitrogen content, and TBA value were increased slowly as storage period was increased at room temperature. Liquid smoke decreased the production of animo nitrogen and VBN. Vacuum packaging was efficient for inhibiting the deterioration and the microbial growth of the seasoned and smoked skipjack tuna powder product.

• Food Science and Preservation
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• v.13 no.4
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• pp.457-464
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• 2006

To improve the functional properties of Gochujang, different amount of skipjack cooking broth (l%, 3%, 5%) were added and their physicochemical properties were examined during storage. During fermentation of Gochujang, pH value decreased and titratable acidity increased, regardless of the amount of skipjack cooking broth. Content of amino-nitrogen increased rapidly at 30 day of fermentation from 171.59 mg% for the control to 191.10 mg% for 5% skipjack cooking broth, and then slightly decreased. It increased with the increase of the amount of skipjack cooking broth. Content of reducing sugar had the highest value at 30 day of fermentation, and then slightly decreased During fermentation, $\beta-amylase$ activity showed the highest value at 30 day of fermentation, and then slightly decreased. Free amino acid content increased with the increase of skipjack cooking broth amount Hunter L a, and b values gradually decreased during fermentation of Gochujang. Based on sensory evaluation of Gochujang after 90 days, Gochujang with the addition of skipjack cooking broth was better than the control in terms of taste, color, flavor, and overall.

• Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.220-225
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• 2007

The movements of skipjack schools during purse seine operations were observed by scanning sonar in the Southwest Pacific Ocean in April 2004. Swimming speed and directional changes were analyzed in relation to heading of the purse seine during shooting, speed of the purse seiner and distance to the net. Escaped schools turned clockwise (relative to the heading of the purse seiner during shooting) significantly more frequently than captured schools, who primarily turned counter-clockwise. The swimming speed of a fish school, whether it was caught or escaped, was somewhat related to the ship's speed, but swimming speed did not differ between captured and escaped schools. The behavior of skipjack schools during purse seining consists of very complex movements with changes in swimming speed and direction in relation to the nets or purse seiner. Therefore, these responses of skipjack schools to purse seining can be useful for modeling the capture process of purse seining in relation to fishing conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.1
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• pp.1-8
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• 2006

For the effective utilization of tuna processing byproducts such as roes of skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacores) as a food resource, the roes of skipjack and yellowfin tuna were examined on food component characteristics and also compared to those of Alaska pollack (Theragra chalcogramma). The concentrations of heavy metal in both roe of the skipjack and yellowfin tuna were below the reported safety limits, therefore, these roes appeared to be safe as a raw material for food resource. The contents of crude protein were 21.4% in the skipjack tuna roe and 21.5% in the yellow fin tuna roe, which showed to be the major component in tuna roes. The prominent amino acids of total amino acids were aspartic acid, glutamic acid, leucine and lysine, and these amino acids were comprise to be 38.4-41.2% of total amino acid in both tuna roes. The total lipid content were 2.1 % in the skipjack tuna roe and 2.0% in the yellofin tuna roe. The major component of total lipid was found to be triglyceride in both tuna roes (skipjack tuna roe, 93.3%; yellow fin tuna roe, 92.0%), which was high in the compositions of 16:0, l8:1n-9, and 22:6n-3. The content of DHA in total lipid of the tuna roes (skipjack tuna roe, 29.9%; yellowfin tuna roe, 36.3%) were higher than that of Alaska pollack roe (18.1%). Based on the results of the proximate composition, mineral, amino acid and lipid characteristic, roes of skipjack tuna and yellowfin tuna showed potential as a raw material for food.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.489-497
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• 2015

To reveal the spatial and temporal variability in the distribution, growth, and maturation of skipjack tuna Katsuwonus pelamis in the western tropical Pacific, we compared two El $Ni{\tilde{n}}o$-Southern Oscillation (ENSO) signals and the sea surface temperature (SST) in the main fishing area with fishery and biological data. An index of skipjack tuna distribution was calculated using Korean purse seine fishery data from 1985 to 2003. Biological data for skipjack tuna were collected monthly from Korean catches during the 1994-2003 period. The catch was more closely related to the SST in the main fishing area than to the ENSO signals. However, cross-correlated function analysis showed delayed interactions between abiotic and biotic factors. The El $Ni{\tilde{n}}o$ events preceded the eastward movement of the fishing center by 2-3 months. El $Ni{\tilde{n}}o$ had a positive effect on the skipjack tuna catch, and the change in the Southern Oscillation Index (SOI) preceded the catch fluctuation by ca. 5-7 months. In addition, negative El $Ni{\tilde{n}}o$ effects on gonad maturation and the mean length of skipjack tuna were detected with time lags of 12 and 7 months, respectively. The length frequency indicated that the regime-specific growth pattern at each discrete period seemed to be related to the ENSO.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.4
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• pp.307-316
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• 2012

This study evaluated the possible use of white muscle from cooked skipjack tuna as a constituent of diet foods. White muscles from the belly and dorsal area of cooked skipjack tuna were identified as anterior, median, and posterior. The skipjack tuna white muscle contained more moisture and ash (except for part I in both the belly and dorsal muscles) than chicken muscle, while it had less crude protein and crude lipid (except for part II in belly muscle). The yield was the highest in part I of both the dorsal and belly parts among the various parts of white muscles. The skipjack tuna white muscle contained 14-18% fewer calories than chicken breast muscle. Part I from both the belly and dorsal muscles had higher total amino acid contents than the other parts, but lower contents than chicken breast muscle. White muscle of skipjack tuna was rich in minerals, such as phosphorus, iron, and zinc. The total free amino acid content of part I in the belly and dorsal muscles was 1,152.1 and 1,215.7 mg/100 g, respectively, and was 1.7-1.8 times higher than in chicken breast muscle. The major amino acids in the white muscles from skipjack tuna were taurine, histidine, anserine, and carnosine. Based on these results, if it is possible to mask the fish odor, all parts of the white muscle from skipjack tuna could be used as constituents of diet foods.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.4
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• pp.219-225
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• 2005

We studied the anticancer, antioxidative, ACE inhibitory, antithrombic, and cerebral ischemia inhibitory activities, of low molecular weight substances fractionated from the seasoned and smoked products of skipjack tuna (Euthynus pelamis). Low molecular weight substances fractionated from the liquid extract of seasoned and smoked skipjack tuna powder showed 7 peaks on gel permeation chromatography. Anticancer activity was the highest at Peak 3 $(54.23%)$ followed by Peak 4 $(41.58\%)$. The potency order of antioxidative activity was the highest at Peak 3 $(94.14\%)$ followed by Peak 2 $(82.07\%)$ and Peak 5 $(81.24\%)$. ACE inhibitory activity was the highest at Peak 3 $(67.27\%)$ followed by Peak 5 $(45.62\%)$. But there was weak anti thrombotic effect (PT and APTT) in the low molecular weight substances of the seasoned and smoked products of skipjack tuna. Cerebral ischemia inhibitory activity was the highest at Peak 3 $(80.0\%)$ followed by Peak 5 $(40.0\%)$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.635-639
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• 2012

Thawing is very important in tuna canning because it affects the yield and quality of the canned tuna, and productivity. The effects of vacuum thawing on the quality, yield, and thawing times of frozen skipjack were compared with conventional water immersion thawing. The time required to thaw frozen skipjack tuna (weight 2.5-3.0 kg) from $-10^{\circ}C$ to $-2^{\circ}C$ was 75, 60, and 37 min at a pressure of 17, 23, and 31 mmHg, respectively, corresponding to temperatures of 20, 25, and $30^{\circ}C$. The thawing time decreased with increasing pressure. Vacuum thawing shorten the thawing time by 58-80% compared with water immersion thawing at $20^{\circ}C$, and there was less difference between the core and skin temperatures than with water immersion thawing. No significant change in pH or histamine was observed according to thawing method, while the volatile basic nitrogen (VBN), trimethylamine (TMA), and K value were lower with vacuum thawing than water immersion thawing. Based on these results, we believe that vacuum thawing minimizes the biochemical and microbial changes that occur while thawing frozen skipjack tuna.