Drying and Characterization of Mint (Mentha spicata L.) by the Cast-Tape Drying Method

Abstract

Mint (Mentha spicata L.) is a medicinal and aromatic plant known for its antioxidant, antiseptic, antifungal, diuretic, and analgesic properties. However, due to its high moisture content, fresh mint is highly perishable, requiring effective preservation methods to ensure its usability. Blanching is commonly applied as a pre-treatment to inactivate enzymes and enhance color and nutrient retention in dried plant materials. Cast-tape drying is a promising process with significant potential for dehydrating and producing dry foods. In this method, circulating hot water facilitates heat transfer via convection and conduction, converting liquid or pasty materials into powder, flakes, or films. This study aims to investigate mint drying using the cast-tape drying method and to analyze the effects of process variables, including circulating water temperature (55°C, 72.5°C, and 90°C), mint paste layer thickness (2, 3, and 4 mm), and blanching. The response variables analyzed include moisture content, color, hygroscopicity, total phenolic content, and chlorophyll and carotenoid levels. Pre-treatment with blanching enhanced color preservation, contributed to faster water removal, and improved retention of bioactive compounds compared to untreated samples. The optimal chlorophyll and carotenoid levels, along with the shortest drying time (approximately 20 min), were observed at 90°C with a 2 mm layer thickness, although phenolic compounds showed a decline. Consequently, cast-tape drying emerges as a viable alternative for producing dehydrated mint with favorable physical and bioactive properties.