• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.6
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• pp.981-986
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• 2000

In the process of tuna for food, the unprocessed parts of the whole fish range from 30 to 35%, which are mostly used as animal feed stuff, and wasted. Thus, preliminary study on the recycling of the by-product was done to ultimately produce highly valuable products. The study was peformed on skin, skin flesh, tail flesh, dark flesh and abdominal flesh of the tuna. First, crude protein was the most abundant in the skin at 26.31%. About 21% of the crude protein were found in the other samples. Second, crude fat was greatly obtained in the skin at 15.58%. Interestingly, only 0.75% of crude fat was found in the dark flesh. Third, vitamin C and vitamin B group were highly measured in the abdominal flesh and the dark flesh, respectively. Importantly, docosahexaenoic acid (DHA, C22 : 6 $\omega$ -3) and eicosapentaenoic acid (EPA, C22 : 6 $\omega$ -3) which are highly unsaturated fatty acids, were abundant in the skin and skin flesh. To determine the effect of high temperature to the unprocessed parts, the samples were exposed to steam for 30 min. After this processing, 15-methylhexadecanoic acid (i-17 : 0) were in- creased in the skin flesh and the dark flesh. Furthermore, 3-hydroxytetradecanoic acid (3-OH 14 : 0), heptadecanoic acid (17 : 0), 2-hydroxyhexadecanoic acid (2-OH 16 : 0) and nonadecanoic acid (19 : 0) hat were not found before with steam were detected. The DHA and EPA in the dark flesh and the DHA in the skin were stable, respectively, even after the treatment.

• Applied Biological Chemistry
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• v.47 no.2
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• pp.197-201
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• 2004

In order to recycle animal by-products from food processing as food seasonings, pig bone (PB), chicken bone (CB) and tuna dark flesh (TDF) were studied. PB and CB extract prepared by hot water extraction for 18 h were hydrolyzed with protease and lipase. The DHs of PB and CB extract were increased to 70% and 80%, respectively, when Flavourzyme was treated after pancreatic enzyme treatment. When TDF was hydrolyzed with Alcalase and Flavourzyme, dry matter yield and total protein yield were around 22% and 9%, respectively. Also the free ammo acid content in hydrolysate reached up to 27% of total solid. The sensory properties of three hydrolysates containing 1% NaCl were, in order of their overall acceptance, TDF, PB and CB. Therefore, tuna dark flesh turned out to be the suitable animal by-product as raw material for seasoning ingredient.