Evaluation of gas freshness indicator for determination of skate (Raja kenojei) quality during storage.

A gas freshness indicator consisting of the pH-sensitive dye bromothymol blue-phenol red (BTB-PR) was investigated for visible color changes of fish product quality based on the quantity of volatile amines. Chromaticity values of the gas indicator accurately tracked an increase in the ammonia content in the packaging headspace of fish products, especially skate (Raja kenojei). Gradual color changes of the gas indicator response correlated with the quality of fish including pH values during storage. Ammonia content was evaluated during the fish storage using headspace solid-phase microextraction analysis with gas chromatography-flame ionization detection. The validation results suggested that good linearity (R²=0.99) and recovery of 84.00%. The limits of detection and quantification were 8.70 and 26.30 mg/L, respectively. A pH values of skate and chromaticity of gas indicator were measured and the correlation with ammonia content was evaluated. Results of this study could prove the application of gas indicator as intelligent package for improvement of food safety.