Blanching-induced microstructural regulation of drying behavior and quality of Gastrodia elata under hot air and infrared-assisted hot air drying

Thermal blanching pretreatment plays an important role in regulating drying behavior and product quality of Gastrodia elata . This study systematically investigated the effects of microwave blanching (MWB), ultrasonic-assisted hot water blanching (USB), and steam blanching (STB) on hot air drying (HAD) and infrared-assisted hot air drying (IR-HAD), focusing on drying kinetics, microstructural evolution, quality attributes, and active ingredient. All blanching treatments effectively reduced polyphenol oxidase and peroxidase activities but induced structural modification and starch gelatinization, which generally prolonged total drying time despite reducing initial moisture content. MWB accelerated early-stage drying and promoted rapid internal temperature increase, whereas STB caused severe tissue collapse and greater color deterioration. IR-HAD shortened overall drying time compared with HAD but exhibited lower effective moisture diffusivity during the falling-rate period, likely due to increased diffusion resistance associated with shrinkage and structural densification. Blanching treatments improved rehydration capacity and altered volatile profiles, with MWB showing stronger suppression of undesirable odor compounds. Moreover, blanching significantly increased gastrodin and parishin A contents while reducing p-hydroxybenzyl alcohol levels, indicating enhanced retention of medicinally relevant components. The results suggest that blanching regulates drying performance through the dynamic interaction between transient permeability enhancement and later-stage diffusion resistance induced by structural transformation. This study provides mechanistic insights into blanching-mediated drying regulation and offers practical guidance for optimizing drying processes of high-value medicinal crops.