RESUMO
Skipjack tuna (Katsuwonus pelamis) belongs to the Scombridae family to determine the consistencycharacteristics of tuna fish loins for 28th days at frozen (−18 ± 2°C) storage. The biochemical, microbial, andsensory quality were analyzed by association of official analytical chemists method, plate count, and QualityIndex method (QIM), respectively. Protein, lipid, and moisture content were found to decrease significantly(p < 0.05) over the study period. Nonetheless, the values of ash, total volatile base nitrogen, tri-methyl aminenitrogen, pH, and peroxide increased significantly (p < 0.05). After 28 days of frozen storage, the total bacterialload in tuna fish loins was reduced from 3.8 × 105 to 3.3 × 104 colony forming unit/g. Total coliforms reducedfrom 113 to 5 Most Probable Number (MPN)/g, fecal coliforms declined to undetectable level from 13 MPN/g,and total Salmonella sp. also decreased from 1 MPN/g to unnoticeable, respectively. Organoleptically tunaloins were found in excellent condition up to 14th days although remained acceptable up to 28th days of thestudy period. The present findings should that the skipjack tuna loins can be retained under an acceptable limitfor human consumption at frozen storage conditions up to 28th days.
RESUMO
Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from the spine (ASC-SP and PSC-SP) and skull (ASC-SK and PSC-SK) of the skipjack tuna, Katsuwonus pelamis, were successfully isolated and characterized. The yields of ASC-SP, PSC-SP, ASC-SK and PSC-SK were (2.47 ± 0.39)%, (5.62 ± 0.82)%, (3.57 ± 0.40)%, and (6.71 ± 0.81)%, respectively, on the basis of dry weight. The four collagens contained Gly (330.2-339.1 residues/1 000 residues) as the major amino acid, and their imino acid contents were between 168.8 and 178.2 residues/1 000 residues. Amino acid composition, SDS-PAGE, and FTIR investigations confirmed that ASC-SP and ASC-SK were mainly composed of type I collagen, and had higher contents of high-molecular weight cross-links than those of PSC-SK and PSC-SP. The FTIR investigation also certified all the collagens had triple helical structure. The denaturation temperatures of ASC-SK, PSC-SK, ASC-SP, and PSC-SP were 17.8, 16.6, 17.6, and 16.5 °C, respectively. All isolated collagens were soluble at acidic pH (1-5) and lost their solubilities when the NaCl concentration was above 2% (W/V). The isolated collagens from the spines and skulls of skipjack tuna could serve as an alternative source of collagens for further application in food, cosmetic, biomedical, and pharmaceutical industries.