Monitoring of headspace total volatile basic nitrogen from selected fish species using reflectance spectroscopic measurements of pH sensitive films.

The release of amines from decomposing fish such as trimethylamine (TMA), dimethylamine (DMA) and ammonia, collectively known as total volatile basic nitrogen (TVB-N), are in high enough concentrations in headspace to be monitored by a colour change in a pH-sensitive sensor. A method developed here uses a pH indicator dye physically trapped in a cellulose polymer film to respond to the headspace TVB-N released from selected fish species during spoilage. Two species were selected for analysis on the basis of economic importance and the levels of volatile amines released were followed with time using uv/vis reflectance spectroscopic measurements. The results show that there is a significant increase in the TVB-N content in the headspace of fish samples after an incubation period of 8-12 h for cod and 12-15 h for orange roughy.