Determination of total volatile basic nitrogen (TVB-N) Total volatile basic nitrogen (TVB-N) was determined through
direct distillation of the fish homogenates after the addition of MgO.
The distillate was collected in a flask containing a 2% aqueous solution of boric acid and a mixed indicator consisted of 0.1% methyl red and 0.1% bromocresol green in ethanol. Afterward, the boric acid solutionwas titrated with 0.1 N H2SO4 solution (Goulas & Kontominas, 2005).
The TVB-N value (mg N/100 g of fish) was determined according to the consumption of sulfuric acid.