Question

3.3 We do not often eat food that is "basic" as our palates generally prefer acidic foods...most fish is basic, provide the net ionic reaction between lemon juice and fish? (3 pts)

Answer 1

When fish die, bacteria begin working to liberate amines from the amino acids in the fish's flesh.Most amines are very pungent, and are the source of many of the "rotting" odors we know.

Some of the amines in fish are known (scientifically!) as cadaverine (C₅H₁₄ N ₂ , produced by the breakdown of lysine), and putriscine(C₄ H₁₂ N ₂ , which is produced by the breakdown of glutamine).

Since amines are basic, mixing them with an acid results in the formation of an amine salt. And this is where the lemon juice comes in .

Sour taste of lemon comes from citric acid (which contains three carboxylic acid groups).

When we squeeze that lemon wedge onto our fish platters, we are setting up a reaction that neutralizes the fishy-smelling amines, thus greatly improving the taste of the fish.

Chemical reaction:

Fish, especially sea fish, naturally contain trimethylamine-N-oxide (CH3)3N−O(CH3)3N−O that, after death, gets enzymatically reduced to trimethylamine (CH3)3N(CH3)3N, the source of ammonia-like fish odour.

In acidic environment, TMA forms water soluble, non volatile, odourless trimethylammonium salts, what eliminates the volatile smelly trimethylamine.

(CH₃)₃N + H⁺ $\rightleftharpoons$ (CH₃)₃NH⁺

It is the direct analogy to the smelly volatile ammonia and odourless ammonium:

NH₃ + H⁺$\rightleftharpoons$ NH₄⁺