Effect of different drying methods on drying characteristics and quality of Camellia oleifera seeds

In order to improve the drying efficiency and product quality, three drying methods of hot air (HA), hybrid infrared-hot air (IR-HA), and hybrid radio frequency-hot air drying (RF-HA) were used to dry fresh Camellia oleifera seeds. The results showed that the shortest drying time was needed, and the minimum shrinkage of C. oleifera seed cells was obtained under hybrid radio frequency-hot air drying than that under hot air drying and hybrid infrared-hot air drying. The oils squeezed from C. oleifera seeds dried by natural air (room temperature), hot air, hybrid infrared-hot air, and hybrid radio frequency-hot air were represented by AO, HAO, IR-HAO, and RF-HAO respectively. The dielectric constant, characteristic peak value of melting heat flux, acid value, and peroxide value of oils squeezed were compared and found that the values of the four indicators of IR-HAO were the highest, but the values of RF-HAO were the lowest. The RF-HAO contains more unsaturated fatty acids, and the quality of RF-HAO was better than that of HAO and IR-HAO. Hybrid radio frequency-hot air drying was the best among the three drying methods of fresh C. oleifera seeds. Practical applications Camellia oleifera seed oil is rich in a large number of fatty acids, of which the content of unsaturated fatty acids can be as high as 93%. The contents of linolenic acid in unsaturated fatty acids were higher than those in sesame oil and soybean oil. Different drying methods on the drying characteristics in this study, microstructure of C. oleifera seeds and the dielectric properties, melting point, acid value, peroxide value of C. oleifera seed oil are analyzed to select the suitable drying technology for C. oleifera seeds. This theory and achievement can provide theoretical guidance for the subsequent processing and storage of C. oleifera seeds.