Effect of Temperature and Moisture Content on the Kinetics of Trypsin Inhibitor Activity, Protein in vitro Digestibility and Nitrogen Solubility of Cowpea Flour

Samples of finely ground cowpea flour containing 7.5%, 19.4% and 25.5% moisture were heated in sealed tubes at 100° 125° and 150°C for periods of 0.5 to 120 min. First order rate constants for losses of trypsin inhibitor activity and nitrogen solubility ranged from 1 × 10 −2 to 18 min −1 and from 4 × 10 −2 to 8 min −1 respectively. In vitro protein digestibility (IVD) increased, then decreased with heating as described by sequential first order kinetics. Rate constants for increase of IVD varied from 0.13 to 12 min −1 , while for decrease in IVD the range was 5 × 10 −5 to 3 × 10 −2 min −1 . Activation energies and relationships between In k and water activity were computed.