Potential beneficial effect of hydrothermal treatment of starches from various sources on in vitro digestion

Abstract

Starches from various botanic origins (maize, quinoa, wheat, potato and rice) were studied. The thermal and pasting properties and their connection with enzyme digestibility were evaluated. Various hydrothermal treatments were applied, taking the starch physical parameters into account, in order to obtain partial and total gelatinisation of the starch structure and determine its influence on enzymatic action. Onset and pasting temperatures of the gelatinisation and pasting processes, respectively, followed the same order in the cereal starches (rice > maize > wheat > quinoa). These results were accompanied by an opposite trend in the percentage of raw starch hydrolysis, with quinoa reaching a level more than 2-fold higher than that of raw maize starch in in vitro digestion kinetics. Other technological parameters, such as high peak viscosity or low breakdown, also reflected modifications in the quinoa starch structure which were related to improved digestibility. However, starch from potato, the only tuber, displayed different characteristics from those of cereal starch, showing greater resistance to digestion. When the starches were pretreated, digestibility increased in all of them compared to their raw counterparts, with the pretreated quinoa and wheat starches showing greater susceptibility to modification of their structure. Although the hydrothermally pretreated maize and rice starches reached about 75% of the hydrolysis index of the corresponding gelatinised starches, raw quinoa had a similar hydrolysis index and quinoa obtained a higher value for total starch hydrolysed. Thus, quinoa starch could be potentially beneficial in the design of more digestible formulations for patients with metabolic disorders such as glycogen storage disease, among others.