Drying Behavior and Curcuminoids Changes in Turmeric Slices during Drying under Simulated Solar Radiation as...

Area of Science:

• Food Science
• Agricultural Engineering
• Traditional Medicine

Background:

• Turmeric (Curcuma longa L.) is widely used as a spice and in traditional medicine.
• Common drying methods include sun and solar drying, impacting quality.
• Understanding optimal drying conditions is crucial for preserving turmeric's bioactive compounds and sensory attributes.

Purpose of the Study:

• To investigate the effects of different drying temperatures (40-70°C) and UV-permeable/impermeable covers on turmeric slice drying characteristics.
• To evaluate the impact of simulated solar radiation on temperature, drying rate, and moisture diffusivity.
• To assess the preservation of curcuminoids and color under various drying conditions.

Main Methods:

• Turmeric slices (2 mm thickness) were dried in a hot-air dryer with simulated solar radiation.
• Two covers were used: UV-impermeable polycarbonate and UV-permeable PMMA.
• Drying temperatures ranged from 40°C to 70°C, with fixed air velocity and relative humidity.
• Drying kinetics were modeled using the Page model; color and curcuminoid content were analyzed.

Main Results:

• Light significantly increased sample temperature under both covers.
• The Page model effectively predicted turmeric drying characteristics.
• Higher temperatures increased drying rates and effective moisture diffusivity.
• Drying at 70°C under either cover resulted in a lower hue angle (more intense orange color).
• Curcuminoid content was negatively affected by cumulative thermal load (CTL), with the lowest content at 40°C under PMMA.

Conclusions:

• The optimum drying condition for turmeric is 70°C under a polycarbonate cover.
• This condition offers a shorter drying time and superior preservation of color and curcuminoids.
• Effective moisture diffusivity is a key factor in turmeric drying kinetics at elevated temperatures.