Howgate P.,Lavender Row 26
Electronic Journal of Environmental, Agricultural and Food Chemistry | Year: 2010
Trimethylamine (TMA) is formed in ice-stored fish from the reduction of trimethylamine oxide (TMAO) by bacteria predominately of the genus Shewanella. In fish harvested from warm waters spoilage is predominately due to bacteria of the genus Pseudomonas and ammonia rather than TMA is produced. TMA concentrations in the flesh of ice-stored fish increases exponentially during storage, perhaps following a dwell period of a few days. The kinetics of the formation of TMA was determined by fitting published data for a large number of species to an exponential mathematical model. The results show a marked difference in kinetics between fish harvested from the wild and fish harvested from aquaculture. The increase in ammonia during spoilage of fish from cold waters is small compared with that from TMA, and the increase in Total Volatile bases (TVB) during storage is mostly due to the production of TMA. Many sets of data on TVB formation during spoilage show the effects of leaching. The variances of TMA and TVB measurements are large, and additionally there are variances between batches due to biological factors. Neither TMA nor TVB are effective indices of spoilage in either commercial quality control, or in official regulatory control.