Question

......... metal ions are not so active accelerators of reversion of oil.

• A. Copper
• B. Cobalt
• C. Zinc
• D. Nickel

Hint:

To prevent metal-catalyzed oxidation, chelating agents like citric acid, phosphoric acid, or EDTA are added to oils to bind pro-oxidant metal ions (especially copper and iron) into ictive complexes.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Flavor reversion and lipid oxidation are major degradative pathways in vegetable oils, leading to the development of undesirable odors and flavors.
Transition metal ions with variable oxidation states act as highly active pro-oxidants by accelerating the decomposition of lipid hydroperoxides into volatile carbonyl compounds.

Step 2: Detailed Explation:
The catalytic activity of metal ions in lipid oxidation depends on their ability to undergo single-electron redox cycles.
Transition metals such as Copper (\(\text{Cu}^{2+}/\text{Cu}^+\)), Cobalt (\(\text{Co}^{3+}/\text{Co}^{2+}\)), and Iron (\(\text{Fe}^{3+}/\text{Fe}^{2+}\)) are highly active pro-oxidants.
They facilitate Fenton-like reactions that generate highly reactive free radicals from stable hydroperoxides.
Nickel (\(\text{Ni}\)), while a transition metal, is less active but can still accelerate oxidation if residual traces remain from the hydrogetion catalyst.
Zinc (\(\text{Zn}\)), on the other hand, is a non-transition metal that exists exclusively in the \(+2\) oxidation state in food systems.
Because it lacks variable oxidation states under storage conditions, Zinc cannot participate in single-electron transfer reactions.
As a result, Zinc ions do not act as active accelerators of flavor reversion or lipid oxidation in edible oils.
Thus, Zinc is the correct choice.

Step 3: Fil Answer:
The correct option is (C).