Question

Anti-nutritional effect of tannins is due to _______.

• A. mineral chelation
• B. protein binding
• C. fat hydrolysis
• D. sugar degradation

Hint:

Tannins are historically used to "tan" leather by cross-linking collagen proteins to make them tough and resistant to decomposition.
This strong affinity for proteins is the same mechanism that makes them anti-nutritive in digestion.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the primary chemical mechanism underlying the anti-nutritional properties of tannins in foods.

Step 2: Key Concepts and Approach:
Tannins are water-soluble polyphenolic compounds found in many plants.
They are known for their astringency, which is caused by their high affinity for binding and precipitating macromolecules.

Step 3: Detailed Explanation:

• Mechanism of Action: Tannins have a high density of phenolic hydroxyl groups.
These groups form strong hydrogen bonds and hydrophobic interactions with the peptide backbone and side chains of proteins.

• Complex Formation: This binding leads to the formation of stable, insoluble tannin-protein complexes.

• Nutritional Impact:
* This process makes dietary proteins resistant to enzymatic breakdown in the gut, reducing protein digestibility.
* Tannins also bind directly to and inhibit digestive enzymes (like trypsin, amylase, and lipase) in the digestive tract, further reducing nutrient absorption.

• Astringency Link: This protein-binding property is also why tannins cause a dry, puckering sensation in the mouth, as they precipitate salivary proteins.

Step 4: Final Answer:
The primary anti-nutritional effect of tannins is due to protein binding.