Selected physical and viscoelastic properties of strawberries as a function of heated-air drying conditions

Abstract

The effect of drying conditions on physical and viscoelastic properties of strawberries was investigated. Drying followed falling rate drying period, indicating that internal resistances limited the water transport within the matrix. Increasing drying temperature and duration led to lower color values, moisture content, and volumes. Strawberries presented linear viscoelastic behavior up to 2.5% strain. Drying caused lower relaxation and higher creep due to the loss of stiffness and structural deformation. Burger’s and three-element Maxwell models were well-fitted to describe creep (R² = 0.971–0.989) and relaxation (R² ≥ 0.999) behaviors of strawberries, respectively. The first Maxwell element demonstrated the viscoelastic behavior of strawberries ($D_{\mathrm{b}1}$ = 0.54–1.51), while the second and the third elements exhibited the viscous behavior ($D_{\mathrm{b}2}$ = 0.069–0.205, $D_{\mathrm{b}3}$ = 0.009–0.047). Strawberries presented solid-like behavior since tan delta (G″/G′) was lower than one for all samples.

Keywords:

• Strawberries
• drying
• viscoelastic
• stress relaxation
• creep

Additional information

Funding

This work was supported by Center for Advanced Research in Drying (CARD) and National Science Foundation (NSF) under the award number 1624812. The authors wish to thank them for providing financial support.