In vitro amylolysis of pulse and hylon VII starches explained in terms of their composition, morphology, granule architecture and interaction between hydrolysed starch chains.

The objective of this study was to understand the factors underlying the susceptibility of pulse (lablab bean, navy bean, rice bean, tepary bean, velvet bean, and wrinkled pea) and hylon VII starches towards in vitro hydrolysis by the combined action of pancreatin and amyloglucosidase. The time taken to reach an equivalent level of hydrolysis (50%) varied significantly among the starches. Changes to molecular order, crystallinity, double helical content, radial orientation of starch chains (polarized light), enthalpy and apparent amylose content during the progress of hydrolysis showed that rate and extent of hydrolysis were influenced both by the structure of the native starches at different levels (molecular, mesoscopic, microscopic) of granule organization, and by the extent of retrogradation between hydrolysed starch chains.

Composition, structure, morphology and physicochemical properties of lablab bean, navy bean, rice bean, tepary bean and velvet bean starches.

The composition, morphology, structure and physicochemical properties of starches from lablab bean, navy bean, rice bean, tepary bean and velvet bean were examined. Starch yield (on a whole seed basis), total lipid, apparent amylose (AM) and starch damage were in the range 20.6-29.9%, 0.48-0.62%, 22.1-32.1% and 0.004-0.011%, respectively. Difference in amylopectin chain length distribution amongst the starches was marginal. The starches differed significantly with respect to granule morphology, molecular order, molecular orientation, double helical content, gelatinization parameters, swelling factor, AM leaching, thermal stability and enzyme hydrolysis. The results showed that interplay amongst differences in molecular order, double helical content, relative crystallinity, AM content, granule morphology and the extent of interaction between and amongst starch chains within the amorphous and crystalline domains, influenced thermal, rheological and digestibility properties.