Ammonia, Dimethylamine, Trimethylamine, and Trimethylamine Oxide from Raw and Processed Fish By-Products

Abstract

ABSTRACT Concentrations of ammonia, monomethylamine (MMA), dimethylamine (DMA), trimethylamine (TMA), and trimethylamine oxide (TMAO) in raw and processed fish by-products were determined in cold-water marine fish using a capillary electrophoresis (CE) method. The CE method provides a fast and sensitive procedure to simultaneously quantify volatile amines and TMAO in raw and processed fish samples. Total volatile bases nitrogen (TVB-N) values were calculated from the concentrations of the respective individual volatile amines detected within the samples. TVB-N calculated concentrations ranged from a low of 12 ± 3.7 mg N/100g (n = 3) to a high value of 119.1 ± 27.2 mg N/100g (n = 3) wet weight for the raw fish by-products and from 60 ± 2.4 mg N/100g (n = 3) to 300.9 ± 40.5 mg N/100g (n = 3) dry weight for the processed fish by-products. No MMA was detected in any of the samples tested. Raw viscera samples contained increased concentrations of DMA and TMA relative to the other samples tested. High levels of TMAO and TMA in the freeze-dried stickwater suggested decomposition of TMAO and/or fractionation into the stickwater during processing since these compounds are water soluble. Results indicated that there is a wide distribution on the levels of TMAO, ammonia, TMA, DMA, and calculated TVB-N in the materials tested. It is possible that these values can be used as quality indicators of raw material freshness and as indicators for the potential to spoil. Values for processed fish by-products tested can also be used as quality indicators.