Identification and stability of trypsin inhibitor isoforms in pea (Pisum sativum L.) cultivars grown in New Zealand

Trypsin inhibitor activity (TIA) of 17 spring-sown field pea cultivars grown in New Zealand ranged from 0.33 to 0.75 TIU/mg DM. These values were much lower than those reported for most European pea cultivars. After soaking and cooking, values fell by 42–91%, with an average reduction of 78% (0.07–0.19 TIU/mg DM). After heat treatment, the residual percentage of TIA was negatively correlated to the amount of TIA in the raw seed. Six to ten trypsin isoinhibitors were observed in each cultivar of the raw extracts, with isoelectric points ranging from 4.6 to 7.6. Only three of the isoinhibitors, with isoelectric points of 5.1, 5.9 and 7.6, remained after heat treatment. ltivars with high TIA levels in the raw seed may be more suitable as processing peas because cooking substantially reduces TIA levels, suggesting that adverse effects of consuming TIA would be limited. Conversely, raw peas with low TIA levels would be more suitable for use as animal feed. Cultivars that contain more unstable isoforms may require less heat treatment, therefore retaining their nutritional value be more suitable for human consumption and use as animal feed, and have reduced processing costs.