Infrared radiation and subsequent hot-air drying increased lipid concomitant contents and improved storage stability of fresh camellia seeds.

Background: Camellia oleifera is a woody oil-bearing crop, and the quality of its seeds and pressed oil is affected by the postharvest drying. In order to find a suitable drying method for camellia seeds maintaining their good qualities, effects of three drying methods, including room temperature (RT) drying, 60 °C hot-air (HA) drying, as well as 600-800 W infrared pre-drying and sequential 60 °C hot-air (IR-HA) drying, on the drying efficiency, qualities and storage stabilities of camellia seeds were compared.

Results: Compared with HA drying, IR-HA drying shortened the drying time of fresh camellia seeds by 42-47%. The IR-HA dried seeds showed brighter color, higher contents of α-tocopherol, γ-tocopherol, β-sterol and squalene, and better oxidation stability than the RT dried and the HA dried seeds. Heat treatments with HA and IR-HA slightly destroyed the microstructure of camellia kernels, changed the compositions and contents of the free phenolics, decreased the activities of lipoxygenases, polyphenol oxidase and lipase, increased the sulfhydryl contents of the enzyme proteins while reduced the α-helix contents of enzyme proteins. However, except for arachidonic acid, the fatty acid profiles of the HA and IR-HA dried camellia seeds were similar to that of the RT dried ones. The obvious decrease of enzyme activities in IR-HA dried seeds could be related to the changed secondary structures of enzyme proteins and the increase of sulfhydryl groups.

Conclusion: The results indicate that IR-HA drying is suitable for obtaining camellia seeds with better quality and higher storage stability. © 2025 Society of Chemical Industry.