Drying Method-Dependent Variations in Phenolics, Color, and Volatile Profile of Thymus praecox subsp. skorpilii

Area of Science:

• Food Science
• Analytical Chemistry
• Phytochemistry

Background:

• Wild thyme (Thymus praecox subsp. skorpilii) is valued for its aromatic and bioactive compounds.
• Drying is a common preservation method, but it can significantly impact the quality of herbs.
• Understanding how different drying techniques affect wild thyme's characteristics is crucial for optimizing its use.

Purpose of the Study:

• To investigate the impact of various drying methods on the volatile profile, total phenolic content (TPC), and color of wild thyme.
• To compare the effectiveness of freeze drying, oven drying, shade drying, and microwave drying (at different power levels).
• To provide practical insights for selecting appropriate drying strategies for wild thyme based on desired quality attributes.

Main Methods:

• Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) for volatile compound analysis.
• Spectrophotometric methods for determining total phenolic content (TPC).
• Colorimetric measurements to assess color changes.

Main Results:

• Drying significantly altered the volatile composition, increasing isoprenoids and decreasing fatty acid derivatives.
• Freeze drying and high-power microwave drying (900 W) demonstrated superior retention of TPC and better color preservation compared to oven and shade drying.
• Increasing microwave power reduced monoterpenes while increasing sesquiterpenes in the volatile profile.

Conclusions:

• Drying methods induce distinct, method-dependent changes in wild thyme's volatile profile, TPC, and color.
• Freeze drying and high-power microwave drying are recommended for preserving the quality attributes of dried wild thyme.
• Selection of drying techniques should align with specific quality targets and processing efficiency for tailored dried thyme production.