Limiting Amino Acids in Pulses and Cereals

Correct Answer: Lysine

The limiting (most deficient) amino acids in plant proteins:

• Pulses/Legumes → Methionine: Legumes like soybean, groundnut, chickpea are rich in lysine but deficient in methionine (a sulphur-containing amino acid).
• Cereals/Grains → Lysine: Maize, wheat, rice, sorghum are deficient in lysine. Maize is also deficient in tryptophan.

Practical Implication — Protein Complementarity

Combining cereals + legumes provides complementary amino acid profiles — cereal's lysine deficiency is covered by legume's lysine richness, and legume's methionine deficiency is covered by cereal's methionine. This is the basis of traditional food combinations (e.g., rice + dal in India).

Maillard Reaction and Lysine

Lysine is the amino acid most susceptible to the Maillard reaction (heat damage). Heating feed causes lysine to become unavailable — this is why overheating during hay and feed processing reduces nutritive value.