A B S T R A C TThe effect of steam treatment on the protein quality and antinutritional factors in beans (Phaseolus vulgaris L ) have been evaluated. The thermal inactivation of total and jhnctional lectins and trypsin inhibitor activity as well as total and available lysine during steam treatment at 102, 119 and 136°C can be described by Jirst order reaction kinetics. Inactivation of trypsin inhibitor factors occurred in two stages with diflerent reaction rates, the initial stage having a higher rate of inactivation. The effect of steaming temperature on the rate constants can be predicted by an Arrhenius-type relation.Part of the total lysine was lost on heating but the amount of available lysine was reduced to a greater extent. The results of the present investigation indicate that steam treatment at 119°C for 5 or 10 min seems to be a good 215 J Sci Food Agric 0022-5142/90/%03.50 0 1990 SCI. Printed in Great Britain

Common beans (Phaseolus vulgarisL