Nutrients and antinutritional factors in faba beans as affected by processing

Abstract

The influence on the nutrients content (soluble sugars, starch, dietary fibre and calcium) and antinutritional factors (α-galactosides and phytic acid) of faba beans (Vicia faba, L. major) of soaking in different solutions (distilled water, citric acid, and sodium bicarbonate solutions), cooking the presoaked seeds, dry-heating and germination have been studied. Soaking brought about a decrease in starch, sucrose, fructose, α-galactoside, dietary fibre and calcium content. Glucose was detected in soaked faba beans and soaking did not modify the phytic acid content. Cooking the presoaked faba beans produced a slight decrease in starch, and caused a general drop in α-galactosides, dietary fibre, calcium and phytic acid, with the exception of seeds presoaked in sodium bicarbonate in which cooking did not cause any appreciable changes in comparison with the unprocessed faba beans. Germination caused a sharp reduction in α-galactoside and phytic acid content after 6 days, whilst starch and dietary fibre decreased slightly. Calcium, however, enjoyed a slight increment during germination which was related to the decrease in the content of hemicellulose and phytic acid. Dry-heating caused a noticeable reduction in all the nutrients and antinutritional factors investigated. Of all the treatments studied, germination appears to be the best processing method to obtain nutritive faba bean flour, since it caused a minor decrease in starch content (15% loss), the largest α-galactoside and phytic acid removal (94% and 45%, respectively) and provided an appreciable amount of dietary fibre.