Effects of thermal processing (blanching and hot-air drying) on key aroma compounds, carotenoid content, total phenolic content, and lipoxygenase activity in carrot

Abstart Carrot ( Daucus carota L. ) is commonly consumed after thermal processing, such as blanching and hot-air drying. However, the individual and synergistic contributions of these two treatments to aroma formation remain unclear. Using SAFE-GC-MS and molecular sensory science, this study compared fresh, blanched, and dried carrots. The critical distinction among the three processing states lies in the shift of aroma contributors: fresh carrots are terpene dominated (22 terpenes); blanching drastically reduces volatile diversity and fruity/sweet notes (OAV≥ 1 compounds drop from 10 to 8); subsequent drying generates abundant aldehydes and ketones via lipid oxidation and Maillard reactions, increasing OAV≥ 1 compounds to 20 and shifting dominant odorants from terpenes to aldehydes/ketones. β -Ionone (OAV 72,843) and trans-2-nonenal (OAV 1,951) are the most important key aroma compounds in hot-air-dried carrots. Kinetic analysis revealed that β -carotene and α-carotene degradation followed first order kinetics (k=1.078 and 0.943h⁻¹), whereas lutein showed complex non-monotonic behavior; non-enzymatic browning followed zero order kinetics (k=0.02089h⁻¹), temporally aligned with Maillard derived volatiles. β -Carotene model systems further identified degradation products, including β -ionone, dihydroactinidiolide, and 4-isopropenyltoluene, and their possible pathways. This work reveals that blanching primarily causes terpene loss, while drying drives aldehyde/ketone formation, and provides kinetic evidence linking carotenoid breakdown to flavor development.