Molecular Size Distribution and Amylase Resistance of Maize Starch Nanoparticles Prepared by Acid Hydrolysis

Abstract

Cereal Chem. 94(2):262-269The molecular size distribution of maize starch nanoparticles (SNP) prepared by acid hydrolysis (3.16M H 2 SO 4 ) and their amylase-resistant counterparts, before and after debranching, was investigated. The weight average molecular weight (M w ) and linear chain length distribution were determined by high-performance size-exclusion chromatography (HPSEC) and high-performance anion-exchange chromatography (HPAEC), respectively. The objective was to understand the role of amylose involvement in the formation of SNP showing different crystalline structures (A-and B-types). The HPSEC profiles of SNP before debranching from waxy, normal, and highamylose maize starches showed broad monomodal peaks. Debranched SNP from waxy maize eluted in a single narrow peak, whereas those from nonwaxy starches showed a multimodal distribution. Similar trends were also observed for the chain length distribution patterns, for which the longest detectable chains (degree of polymerization [DP] 31) in waxy maize were significantly lower than those of nonwaxy maize starches (DP 55-59). This indicated the potential amylose involvement in the SNP structure of normal and highamylose starches. Further evidence of amylose involvement was ascribed to the resistance of SNP toward amylolysis (Hylon VII > Hylon V > normal > waxy). The amylase-resistant residues of SNP from high-amylose maize starches were composed of both low M w linear and branched chains. † Corresponding

Physicochemical studies of nanocrystals of starches from two rice (Oryza sativa L.) types and their characteristics using various modern instrument techniques

“…This could be due to the presence of an electrical double layer around the SNCs, and/or formation of aggregations in aqueous suspensions, which resulted in the larger diameter measured using DLS. Similar phenomena have been reported previously 16,26 …”

“…This could be ascribed to the differences in granule size, granule porosity and amylose content in materials used. M w of NSNC (1.45 × 10 4 Da) and WSNC (1.72 × 10 4 Da) was significantly lower than that of rice starches (from 4 to 15.8 × 10 8 Da) reported in previous literature ( P < 0.05), 30 which is related to the degradation of both amylose and amylopectin after acid hydrolysis 26 . NSNC and WSNC had similar zeta potential values (measured at a pH of 6.0) of around −20 mV, which was in agreement with previous findings 31 .…”

“…The molecular weight determination was based on a modified method reported by Liu et al 25 . and Perez Herrera et al 26 . SNCs (1.5 mg mL −1 ) were thoroughly dissolved in 4 mL of 90 wt% dimethylsulfoxide in boiling water, with constant magnetic stirring for 24 h. Then, the samples were filtered through a 0.45 μm PTFE filter and 100 μL of SNCs was injected into the GPC instrument.…”