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 (Jmax), instantaneous compliance (J0) and retardation compliance (J1) of modified starch increased proportionally with increasing creep time and shear stress but decreased with increasing temperature. The Newtonian viscosity (η0) 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 (R2 > 0.918). CONCLUSIONS Modified starch pastes exhibited time‐, stress‐ and temperature‐dependent creep‐recovery behavior. The Jmax values of modified starch pastes were low(<0.20 Pa−1) and the η0 values high (>3.5 × 103 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

The viscoelastic properties of soy protein isolate (SPI) were investigated by creep–recovery under creep time (75 s, 150 s, 300 s, and 600 s), shear stress (1 Pa, 6 Pa, 10 Pa, and 20 Pa), and creep temperature (25°C, 50°C, and 80°C). Creep compliance (JC) increased proportionally with creep time from 75 to 600 s and with stress from 1 to 20 Pa, it decreased proportionally with temperature from 25 to 80°C. Results showed that the flow behavior of SPI varied along with creep time, stress, and temperature. Creep compliance data were best‐fitted to 4‐element Burgers model (R2 > .94), the instantaneous compliance (J0), retardation compliance (J1), retardation time (r1), steady‐state viscosity (η0), and recovery (%) have significant changes with creep time, stress, and temperature (p < .05). Adding maltodextrin (MD) accelerated the deformation of SPI. The flexibility and rigidity of SPI molecular chains was dependent on creep time, stress, and temperature. Practical applications In this research paper, we studied the viscoelasticity of SPI using the creep–recovery analysis. The chain flexibility, rigidity, and viscidity of SPI molecules were discussed at creep time, shear stress, and creep temperature. At the same time, the viscoelasticity of SPI adding of MD is also discussed. According to the experiment, this study provides new insights into the viscoelastic properties of SPI and builds a fundamental foundation for the comprehensive utilization of SPI in the food industry.