Evaluation of a freshness indicator for quality of fish products during storage

A freshness indicator consisting of a polymer matrix solution containing the pH-sensitive dye bromocresol green was investigated for monitoring visible color changes of fish spoilage volatile compounds based on the quantity of volatile amines. Mackerel fillets were inoculated with Pseudomonas fragi and stored in incubators at 5, 12, 18, and 25°C. Chromaticity values of the freshness indicator accurately tracked an increase in the trimethylamine content in the packaging headspace. Gradual color changes of the freshness indicator response correlated with the quality of fish, including growth of P. fragi and pH values during storage. Results will be useful to establish a basis for development of a freshness indicator and to determine the suitability of freshness indicator formulations for intelligent food packaging applications.