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Abstract

The effects of storage temperature (-20°C, -30°C and -55°C) on selected quality-related characteristics of vacuum packed frozen giant grouper fillets (Epinephelus lanceolatus) stored for 6 months were evaluated. The following quality attributes were measured: proximate composition, pH, thiobarbituric acid (TBA) value, total volatile basic nitrogen (VBN), ATP related compounds, K value, microbiological analysis, color, texture and sensory evaluation. Formation of TBA was low in the giant grouper fillet, with a value of less than 3.91 mg malondialdehyde (MDA) kg-1, after 6 months storage at -30 and -55°C. No significant differences were found in pH, total plate count (TPC), white index (WI) or color value when fish were stored at different temperatures. All fillets stored under -55°C had K values lower than 20%, indicating the fillets were still in very fresh condition even after four months storage. The texture profile and hardness increased significantly with storage duration. Particularly, the raw giant grouper fillet stored at -55°C showed the greatest increase in hardness after 6 months storage compared to the other two storage temperatures. Significant differences in sensory attributes were barely detected by 56 panelists. For giant grouper fillets, little improvement in quality was found using ultra low storage temperature (-55°C) compared to the storage at -30°C. Accordingly, storage temperature at -30°C is considered the most economical and appropriate practice in preserving giant grouper fillets for commercial purposes.

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