1. A laboratory-prepared groundnut flour defatted at room temperature (DGF) was subjected to dry heat or to pressure steaming under varying conditions of time and temperature, and its amino acid composition and nutritive value, the latter assessed by a chick growth test—the gross protein value (GPV) test, were compared with those of some commercial groundnut meals. Trypsin inhibitor activity, available lysine value (ALV) and ‘arachin’ and ‘conarachin’ content and, in some instances, GPV were estimated in the heated samples.
2. The amino acid composition of the DGF and of commercial meals of high, medium and low GPV did not differ markedly, and the GPV of the DGF fell within the range of the three commercial samples.
3. Both dry and moist heat under specified conditions lowered ALV in the DGF and in the ‘arachin’ fractions, but had little effect on the ALV of the ‘conarachin’ fraction.
4. Moist, but not dry, heat rapidly removed trypsin inhibitor activity, and dry, but not moist, heat lowered GPV.
5. Neither ‘conarachin’ content nor trypsin inhibitor activity correlated with GPV in a range of commercial groundnut meals.
6. Dry heat (125. for 5 h) lowered nutritive value and ‘conarachin’ content but did not reduce the amount of total nitrogen soluble in sodium chloride solution.
7. No trypsin-inhibiting activity was found in the testa (skins) but these did exhibit growth-depressant properties for chicks. This property was removed by mild moist heat treatment.
8. ‘Arachin’ isolated from a commercial groundnut meal was valueless as a protein supplement for a cereal ration for chicks; ‘conarachin’ by itself, and mixed with arachin (1:3) was equivalent in GPV to the parent meal.
9. A factor other than those considered here, and possibly unassociated with processing, is primarily responsible for the differences in growth-promoting qualities of the commercial groundnut meals used in this work.