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Effect of the viscoelastic properties of modified starch as a wall material on the surface morphology of microcapsules
Author(s) -
Zhang Chunyu,
Xie Yanli,
Zou Junjun
Publication year - 2019
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.9713
Subject(s) - creep , starch , materials science , viscoelasticity , composite material , rheology , viscosity , chemistry , food science
BACKGROUND Since microcapsule technology has a good protective effect on unstable bioactive substances, many studies have focused on exploring the best technical conditions for forming microcapsules. Modified starch is a microcapsule wall material with good emulsifying and film‐forming properties. The objective of this work was to study the creep‐recovery behavior of modified starch pastes for various creep time, shear stress and temperature. Furthermore, the effect of creep‐recovery behavior on the morphology of microcapsules made of the modified starch was investigated. RESULTS The maximum creep compliance ( J max ), instantaneous compliance ( J 0 ) and retardation compliance ( J 1 ) of modified starch increased proportionally with increasing creep time and shear stress but decreased with increasing temperature. The Newtonian viscosity ( η 0 ) increased with increasing creep time and temperature but decreased with increasing shear stress. The recovery rate of the modified starch pastes varied from 0.92 to 33.68% in the creep‐recovery test conditions. Creep‐recovery data could be well explained by a four‐parameter Burgers model ( R 2 > 0.918). CONCLUSIONS Modified starch pastes exhibited time‐, stress‐ and temperature‐dependent creep‐recovery behavior. The J max values of modified starch pastes were low(<0.20 Pa −1 ) and the η 0 values high (>3.5 × 10 3 Pa s) for all test conditions. The results revealed the modified starch pastes had a good rigid network structure to resist deformation but recovery was difficult once deformation occurred. Microcapsules produced using the modified starch exhibited a small deformation with regular spheres and some dents, consistent with the results of creep‐recovery tests. © 2019 Society of Chemical Industry