The measurements of the TVB-N were performed according to
the method described by Etemadian et al. (2011). The samples
(3.0 g) of surimi were homogenised for 2 min with 3.0 mL of
distilled water and 6.0 mL of 10% trichloroacetic acid. After the
homogenisation was complete, 18.0 mL of 5% trichloroacetic acid
was added. The mixture was centrifuged at 3000 g and 4 C for
10 min, and then 5% trichloroacetic acid was added to obtain a total
volume of 30 mL. One millilitre of the sample solution and 1.0 mL of
a K2CO3 solution were then placed on the outer section of a Conway
micro-diffusion cell, and the mixture was stirred gently. The cell
was incubated at 37 C for 60 min and then titrated against 0.02 N
sulphuric acid. The concentration of TVB-N was calculated as
ammonia equivalents using the following equation: