Studies on the Dried Agar Jelly

Part III. Drying test of agar jelly

Abstract

Effects of drying temperature and relative humidity on drying rate of agar jelly were studied.
When jelly was stored under various relative humidity (RH0-90%) at 300°C, jelly was driedbelow RH 80% and drying rate was similar to each other under RH0-43%.
When dried at 40°C, 50°C and 60°C under RH40%, 60% respectively, drying rate of jelly was increased as the temperature rose and was delayed as jelly moisture decreased, especially, under the low humidity.
These results indicated that the delay of drying rate was due to over-drying of the surface of jelly.
Changes of physical properties of jelly on various drying stage at 50°C and 60°C were measured.
The gel strength of jelly was unchanged till its moisture content was decreased 6-7% from initial moisture, after that its values were increased rapidly with decreasing of moisture content.
On the creep test, E₁ (Young modulus of Hooke type)was increased but E₂, E₄ and η₂ (Young modulus of Voigt type and Plasto-elastic type, viscosity of Voigt type) were decreased with progress of drying stage.
The chages of η₃ (viscosity of Newtonian type) were decreased at 50°C of drying temperature but increased at 60°C.
Those all elements were remarkably changed on drying at 50°C than at 60°C.