Changes in levels of phytic acid, lectins and oxalates during soaking and cooking of Canadian pulses

Abstract

Raw and processed (soaked or cooked) seeds of peas, lentils, chickpeas, fava beans and common beans were studied for their contents of antinutritional factors (lectins, phytic acid, total and soluble oxalates), along with soybean as a control. Analysis of variance indicated that legume type, treatment and their interactive effects were significant on these antinutrients. The raw soybean seed was found to contain the highest levels of lectins (692.8 HU/mg), phytic acid (22.91 mg/g), total oxalate (370.5 mg/100 g) and soluble oxalate (200.7 mg/100 g) among all investigated seeds. Relatively high contents of lectins were detected in beans (87.69–88.59 HU/mg) and other pulses ranging from 2.73–11.07 HU/mg. Phytic acid in Canadian pulses varied slightly from 8.55–22.85 mg/g. Total oxalates were variable, ranging from 244.7–294.0 mg/100 g in peas, 168.6–289.1 mg/100 g in lentils, 241.5–291.4 mg/100 g in fava beans, 92.2–214.0 mg/100 g in chickpeas and 98.86–117.0 mg/100 g in common beans. Approximately 24–72% of total oxalate appeared to be soluble in all investigated pulses. Soaking the seeds in distilled water significantly decreased the contents of lectins (0.11–5.18%), total oxalate (17.40–51.89%) and soluble oxalate (26.66–56.29%), but had no impact on phytic acid. The cooking process was found to be more effective in reducing levels of all the investigated antinutritional factors, except phytic acid in common beans and soybean.