Development of a novel Mohr’s salt-based indicator for monitoring sea bass (Lates calcarifer) fillet spoilage in chilled storage

Abstract

A novel Mohr’s salt-based indicator was investigated with prospects for developing diagnostic packaging, as a chemical sensor for simultaneous observation of sea bass (Lates calcarifer) fillet putrefaction. In addition, the correlation was assessed between the microorganism enumeration and volatile compound quantification. This attached-to-package sensor consists of ammonium iron (II) sulfate hexahydrate ([NH₄]₂Fe[SO₄]₂·6H₂O), termed Mohr’s salt. Total volatile basic nitrogen (TVB-N) compounds such as ammonia, dimethylamine and trimethylamine were used as indicators of deteriorating metabolites since the extent of deterioration was associated with the quantity of heightened TVB-N throughout shelf life. Attributes of these sensing solutions were investigated, including their connection with NH₃. Then these indicator labels were prepared using solution casting. The appropriate formula consisted of Mohr’s salt 0.1% weight per volume and acetic acid 0.05 % volume per volume (v/v) or 0.10 % v/v. The color changes (from colorless to dark green) for the total color difference of the Mohr’s salt-based indicator corresponded well with the extent of TVB-N in the sea bass fillet. Experiments on fish fillets confirmed that the indicator signal was associated with the increased growth of microorganisms, which possibly allowed for concomitant observation of putrefaction.