Topics:
Animal Nutrition, Animal Refresher
Amino Acid Susceptible to Maillard Reaction
An amino acid which is mainly susceptible to Maillard type reaction is:
- Leucine
- Lysine — Correct Answer
- Methionine
- None
Explanation:
Correct Answer: Lysine
Lysine is the amino acid most susceptible to the Maillard-type reaction because its ε-amino group (side-chain −NH₂ of the ε-carbon) is highly reactive with reducing sugars. This reaction renders lysine biologically unavailable, even though it is still detected chemically as nitrogen by the Kjeldahl method.
Why Lysine is Most Susceptible
| Property | Lysine | Other Amino Acids |
|---|---|---|
| Reactive group | ε-amino group (−NH₂ on side chain) | Only α-amino group (blocked in peptide bond) |
| Availability of −NH₂ | Free and highly reactive | Less accessible (in peptide bonds) |
| Consequence of Maillard reaction | Unavailable lysine → reduced protein quality | Less severely affected |
Nutritional Consequences
- Maillard-damaged lysine is called "bound lysine" or "unavailable lysine".
- It is detected as nitrogen by Kjeldahl (inflates apparent CP) but cannot be hydrolyzed or absorbed.
- This is why reactive lysine tests (FDNB method) are used to assess true nutritional value of heat-processed feeds.
- Lysine is the first limiting amino acid in pigs and second limiting in poultry — so its loss is economically significant.
Why Other Options Are Wrong
- Leucine → less susceptible; side chain is a non-polar isopropyl group with no free amino group.
- Methionine → sulphur-containing; may be oxidized but less reactive with sugars in Maillard browning.
- None → Lysine is definitively the most Maillard-susceptible amino acid.
