Effect of starch concentration and resistant starch filler addition on the physical properties of starch hydrogels

Corn starch-based hydrogels are safe and biodegradable polymers with a wide array of applications in food science. The aim of this study was to investigate the effects of starch and natural filler resistant starch type 2 (RS2) particles concentration on the textural properties of corn starch hydrogels. Native starch (NS) hydrogels of 8%, 10%, 12%, and 15% w/v were prepared; in each of these dispersions, part of the NS was substituted with RS2 to a concentration of 2% or 10%. NS hydrogels with the highest concentrations had the maximum hardness, cohesiveness, and gumminess values, whereas the addition of RS2 particles did not affect gel textural properties. Native and substituted RS2 hydrogels showed close similarities in their rheological and textural characteristics. Water-holding capacity greatly decreased with increasing starch concentration, suggesting that the hydrogels with the highest NS concentration had the densest network as depicted by SEM micrographs. Subsequently, hardness, gumminess, and consistency coefficient were linearly correlated to starch concentration and storage time. Fluid release was exponentially dependent on starch concentration. The degree of crystallinity by X-ray diffraction (XRD) indicated that by increasing starch concentration and substitution level, crystallinity increased. Consequently, NS concentration determined the textural properties of corn starch hydrogels. On the other hand, RS2 substitutions did not affect any of these parameters, indicating their potential role as inactive fillers with a beneficial effect on the maintenance of normal blood glucose levels. Therefore, the consistency of a food gel can be optimized by changing the ratio of inactive filler to starch gel matrix.