TVB-N content was determined by distillation after the addition of MgO to the minced sample. The distillate was collected in a flask containing 3% (w/v) aqueous solution of boric acid and a mixed indicator produced by dissolving 0.1 g of methyl red and 0.05 g methylene blue to 100 mL ethanol. The boric acid solution turned green when the distilled TVB-N made it alkaline. Finally, the boric acid solution was titrated with a 0.01 mol/L HCl solution until it turned pink (Goulas & Kontominas, 2005). The quantity of TVB-N in mg/100 g sample was calculated from the volume (V) of HCl added and its