Impact of reagent infiltration time on reaction patterns and pasting properties of modified maize and wheat starches

•A longer reagent infiltration time increased reaction uniformity within granules.•Amylose (AM) was reacted more than amylopectin (AP) for all infiltration times.•AM:AP reactivity increased with increasing granular reaction uniformity (wheat starch).•Pasting viscosity decreased (cross-linking) as the reagent infiltration time increased.•Granular/molecular reaction locale impacts pasting properties of starch derivatives.

The impact of granular and molecular reaction patterns on modified starch properties was investigated as a function of the length of time allowed for reagent to infiltrate starch granules. A fluorescent reagent [5-(4,6-dichlorotriazinyl)aminofluorescein] was dispersed in aqueous normal maize or wheat starch slurries (35%, w/v) for 0, 5, 10, 30, or 60 min, after which reaction was initiated by increasing the pH to 11.5 and allowing reaction to proceed for 3 h. With increasing lengths of infiltration, the reaction became increasingly homogeneous within the granule interior (matrix) and the AM:AP reactivity ratio increased (wheat starch), as assessed by confocal laser scanning microscopy (CLSM) and size-exclusion chromatography (refractive index and fluorescence detection), respectively. A longer reagent infiltration time also led to a more inhibited (i.e., cross-linked) pasting viscosity, suggesting that both granular and/or molecular reaction patterns were altered by varied reagent infiltration times to ultimately impact modified starch properties.