Jharkhand PSC Prelim Exam 18-Dec-2016 Solved Paper

(4) Foul smell from dead fish and decaying flesh is due to diamines released by the bacterial decomposition of protein.
The compound trimethylamine(TMA) is an important component of the typical fishy smell of marine fish that has been stored for some time. In fact, it is the presence of trimethylamine that is used as an indicator of how fresh a fish is. The breakdown of protein into low-weight amines(trimethylamine), nitrogen containing compounds is what gives fish a fishy smell . It reacts with water to produce hydroxide ion:
${\left({\mathrm{CH}}_3\right)}_3\mathrm{N}+{\mathrm{H}}_2\mathrm{O}\to {\left({\mathrm{CH}}_3\right)}_3{\mathrm{NH}}^{+}+{\mathrm{OH}}^{+}$