Premium
Effects of cross‐linking on the rheological and thermal properties of sweet potato starch
Author(s) -
Kim BeaYoung,
Yoo Byoungseung
Publication year - 2010
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.201000035
Subject(s) - rheometry , differential scanning calorimetry , rheology , starch , materials science , swelling , dynamic mechanical analysis , elastic modulus , dynamic modulus , potato starch , food science , composite material , chemistry , polymer , thermodynamics , physics
Sweet potato starches were modified with three different concentrations of phosphorus oxychloride (POCl 3 ) (0.01, 0.02, and 0.03%, based on dry weight of starch) as a cross‐linking agent. The effects of crosslinking on rheological and thermal properties of sweet potato starch (SPS) pastes were evaluated. Cross‐linking considerably reduced the swelling power, consistency index ( K ), apparent viscosity ( η a ), and yield stress ( σ oc ) values of SPS, which significantly decreased with increase in POCl 3 concentration. The gelatinization temperature ( T p ) and enthalpy (Δ H ) values of the cross‐linked SPS, which were determined using differential scanning calorimetry, were higher than those of native SPS. Storage modulus ( G ′), loss modulus ( G ″), and complex viscosity ( η *) of the cross‐linked SPS pastes determined using small deformation oscillatory rheometry, were higher than native starch, and they also decreased with increase in POCl 3 concentration from 0.01 to 0.03%. The tan δ (ratio of G ″/ G ′) values (0.15–0.19) of the cross‐linked SPS samples were much lower than that (0.37) of the native SPS, indicating that the elastic properties of the SPS pastes were strongly influenced by modifications from cross‐linking. Finally, Cox–Merz plots showed that η * was much higher than η a for the cross‐linked SPS pastes.