51A-18

S. Metin¹, F. KOREL¹, and M. O. BALABAN. (1) Food Science and Human Nutrition Department, University of Florida, P. O. Box 110370, Gainesville, FL 32611

1. Justification

Mullet (Mugil cephalus) is a common fish worldwide. Its spoilage is caused by microbial activity, chemical and enzymatic reactions. These are affected by storage time and temperature, and the gas atmosphere over the fish. Current quality evaluation methods depend on sensory methods. Electronic nose could automate and make this evaluation more objective.

2. Objectives

The objectives of this study were to determine the changes in odor, microbial counts, and sensory attributes of fresh mullet fillets stored under modified atmospheres at different temperatures over time, and to correlate electronic nose data with microbial results and sensory evaluation.

3. Methods

Fresh mullet (Mugil cephalus) fillets were stored at 1.7° and 7.2°C for up to 15 days under atmospheres of air, 100% CO₂ and 60% CO₂ +40% air. The odor of the fillets were measured by an electronic nose (EEV, Inc.) every three days. Fillets were also evaluated for odor attributes during storage by a trained sensory panel using a pre-defined 9-point scale with verbal descriptors. Aerobic counts were performed by using 3M petrifilms.

4. Results

Data were analyzed using discriminant function analysis. The electronic nose was able to detect odor changes during storage at 1.7° and 7.2°C under different atmospheric conditions. When grouping by microbial load, the correct classification rates for the discriminant functions at 1.7°C were 95%, 97% and 85% for the air, CO₂ and modified atmosphere condition, respectively. When grouping by sensory scores for samples stored under modified atmosphere , the classification rates were 92% and 97% for the 1.7° and 7.2°C, respectively.

5. Significance

The electronic nose was able to correlate the odor of mullet fillets with microbial load, modified atmospheric conditions, storage time and temperature. After rigorous training, the electronic nose is potentially a valuable tool to measure quality.