Starch characteristics of black bean, chick pea, lentil, navy bean and pinto bean cultivars grown in Canada

The physicochemical properties of starches from different cultivars of black bean, chick pea, lentil, navy bean, smooth pea and pinto bean were examined. Starch granule size ranged from 8 to 35 μm. The starch granules were round to elliptical with smooth surfaces. The total amylose content ranged from 23.0 to 29.5%, of which 6.0–14.9% was complexed by native lipid. All starches showed a ‘C’ type X-ray pattern. The peak at 2θ=5.54 (characteristic of B type starches) was most pronounced in pinto bean and black bean starches. Relative crystallinity followed the order: pinto bean>lentil∼smooth pea∼chick pea∼black bean∼navy bean. The swelling factor (at 80 °C) followed the order: black bean>smooth pea∼chick pea>lentil>navy bean>pinto bean, whereas, amylose leaching (at 80 °C) followed the order: lentil>smooth pea>chick pea>black bean>navy bean>pinto bean. Pinto bean starches showed the highest gelatinization transition temperatures and enthalpies of gelatinization, whereas, the highest gelatinization temperature range was exhibited by black bean starches. All legume starches exhibited high thermal stability during the holding cycle (at 95 °C) in the Brabender viscoamylogram. However, they differed significantly with respect to the viscosity at 95 °C and the degree of set-back. These differences were more pronounced in pinto bean starches. The extent of syneresis followed the order: black bean>chick pea∼lentil>smooth pea>navy bean>pinto bean. Differences in physicochemical properties were more marked among cultivars of black bean, and between cultivars of chick pea and smooth pea starches. This study showed that black bean and pinto bean starches differed significantly from each other, and from the other starches, with respect to the magnitude of interaction between starch chains within the amorphous and crystalline domains.