CHEMICAL CHANGES OF SHORT-BODIED MACKEREL (Rastrelliger brachysoma) MUSCLE AT CHILLED AND FROZEN STORAGE (Perubahan Kimia ke atas Tisu Otot Ikan Kembung Bertubuh Pendek (Rastrelliger brachysoma) Pada Penyimpanan Suhu Dingin dan Sejuk Beku)

This study was carried out to evaluate the chemical changes in short-bodied mackerel during chilled (4 °C) and frozen (-18 °C) storage for 18 days. The chemical changes were monitored at three days interval using Peroxide Value (PV), Thiobarbituric Acid (TBA), Total Volatile Base Nitrogen (TVBN) and Trimethylamine (TMA) tests. The PV of both chilled and frozen mackerel significantly increased (p < 0.05) with storage time and the rate was significantly higher in chilled than frozen mackerel. Based on the results, the chilled and frozen mackerel started to become rancid at day 15 and day 18, respectively. Similar trend was observed for TBA value, where the malonaldehyde content significantly increased (p < 0.05) for both chilled and frozen mackerel with storage time, and the rate of increase was higher in chilled than frozen mackerel. The TVBN and TMA of chilled mackerel increased significantly during storage time, but the values declined in frozen mackerel which might be due to inhibitory effects of freezing on the bacterial activities and hence avoid accumulation of TMA. Based on the chemical analyses, chilled mackerel spoiled rapidly compared to frozen mackerel.