Thermal conversion of trimethylamine-N-oxide to trimethylamine and dimethylamine in squids.

The levels of dimethylamine-nitrogen (DMA-N), trimethylamine-nitrogen (TMA-N) and trimethylamine-N-oxide-nitrogen (TMAO-N) were determined in five species of dried squid. Each sample contained extremely high levels of TMAO-N (2558-8064 ppm) and moderate amounts of TMA-N (121-503 ppm) and DMA-N (124-373 ppm). Over 90% of TMAO-N in squid was converted to TMA-N and DMA-N after heating at 200 degrees C for 1 hr; approximately 50% of the volatile TMA-N and DMA-N was lost during the course of the heating. The thermal conversions were accelerated by heat, and possibly involved catalysis by certain tissue constituents. Squids are a popular seafood in most oriental countries, but before appearing on the market they are subjected to a long food-processing procedure. Therefore, a high concentration of TMAO in squids is an important problem, for food technology as well as toxicology.