| 英文摘要 |
Milkfish (Chanos chanos) aquaculture is an important sector in Taiwan, but little study has been done on the meat quality of milkfish. The objective of this project is to investigate chemical compositions, flavoring-related components, and sensory evaluation of milkfish raised with different diets and culture methods. Six different cultured fish (32, 8, 2 ppt salt water, fresh water, mixed cultured with gracilar and hard clam) and wild fish were sampled from Tainan, Gangshan and I-Lan, respectively. The gracilar and Gangshan groups showed lower condition factor (CF) and hepatosomatic index (HSI) as compared to other cultured fish. The ratio of deposit fat was about 0.03% except gracilar group with 0.02%. Wild fish had larger weight, longer body length and tail fin, and darker color in dorsal portion. They also had much larger front stomach than cultured fish, but .CF, HIS and deposit fat were much lower. The pH value (5.40?5.78), ammonia (3.30?5.07 mg/100g) and salt (0.83?1.0%) in the muscles of seven fish groups showed no remarkable differences; however, the 8 ppt group had a lower pH value. The fat content in the muscle of wild fish was lower than those of cultured fish. Different cultured fish also showed differences in fat contents, of which gracilar group had a lower content. The amounts in ventral muscle were higher than the dorsal muscle. As compared to the muscle, viscera had much higher fat with the level of 18%. The protein contents in all groups wwere more than 20%. Inosine 5’-monophosphate (IMP), a taste substance, was the dominant compound of nucleotide-related compounds (NRC) in milkfish muscle. Wild fish had the highest amount of NRC. The predominant free amino acids (FAA) was histidine, followed by taurine and arginine. Wild fish also had the highest amount of FAA, and the 8 ppt group had the lowest level. Carosine, a dipeptide, was detected in a small amount in all fish. According to results of sensory evaluation, no remarkable difference was found between salt-water cultured and fresh-water cultured fish. The cook had higher scores for the former, but no statistic significance was found. |