Modification of resistant starch nanoparticles using high-pressure homogenization treatment

Abstract

High amylose (HA) maize starch, rich in amylose (more than 55%), belongs to the category of resistant starch type 2 (RS2), and therefore has a specific structure resistant to digestion. The purpose of this study was to modify HA maize starch, reducing its particle size. A mechanical treatment was used, applying high-pressure homogenization (HPH) at different pressure conditions 140, 200 and 250 MPa and treatment cycles, ranging from 1 to 4. The impact of HPH on starch structure, including size, morphology and crystallinity as well as on the amylose content was investigated. The granule particle size was measured by Dynamic Light Scattering (DLS), their morphology using Scanning Electron Microscopy (SEM) and the degree of crystallinity by X-ray diffraction (XRD). According to the results the smallest particle size, 540 nm, was achieved after 4 cycles of homogenization at 250 MPa. It was found that the pressure applied was more significant to reduce granules’ size than the time of treatment. Αt intense pressure the granules structure has changed as pores, deep slots and aggregates were observed. The amylopectin structure was destroyed resulting in an increase in amylose:amylopectin ratio. However, size reduction was not accompanied by any structure conversion and HA maize starch remained a B-type starch. According to the information found a further understanding of the effect of HPH on modifying HA starch was achieved. Physically modified RS could result to different food applications.