What is an effect of heat treatment such as toasting or extrusion on anti-nutritional factors in soybean meal?

• A. Heat reduces trypsin inhibitors and lectins, improving protein digestibility.
• B. Heat increases lysine availability beyond original levels.
• C. Heat completely destroys all essential amino acids.
• D. Heat does not affect anti-nutritional factors.

Answer: (A)

Heat processing of soybean meal, through methods like toasting or extrusion, reduces anti-nutritional factors such as trypsin inhibitors and lectins. Trypsin inhibitors block pancreatic enzymes, limiting protein digestion, while lectins can interfere with nutrient absorption and gut function. Denaturing these compounds with heat removes their inhibitory effects, letting digestive enzymes access proteins more effectively and improving overall protein digestibility. While this processing can boost digestibility, it doesn’t increase lysine availability beyond its original level—excessive heat can actually reduce lysine due to Maillard reactions. Also, some heat-sensitive amino acids may be damaged if overheating occurs, so processing aims to inactivate anti-nutritional factors without overdoing heat.