Salt intervention for the diversities of essential oil composition, aroma and antioxidant activities of Kushui rose (R. setate×R. rugosa)

Increasing the output of essential oil (EO) has always been a concern during production, and this challenge has gained more attention from the essential oil industry. The salt process in which petals are immersed in sodium chloride solution in the process of hydrodistillation can effectively enhance the yield of EO, but it is unknown whether the quality of the EO changes after such treatment. Therefore, this study was designed to compare the properties of fresh rose essential oil (FREO) and salt rose essential oil (SREO), including compositions and their contents, characteristic aroma compounds and aroma profiles, as well as antioxidant activities. In the first part of the investigation, the compounds in FREO and SREO were identified by gas chromatography-mass spectrometry (GC/MS) and two-dimensional gas chromatography and time-of-flight mass spectrometry (GC × GC-TOF/MS). The aroma research was evaluated using the odor activity values (OAV), and the antioxidant properties were investigated for the total antioxidant capacity and the ability to scavenge DPPH free radicals. The results identified the 191 and 190 components in FREO and SREO using one-dimensional (¹D) GC and two-dimensional (²D) GC, respectively; both were characterized by a high alcohol content, represented particularly by citronellol, geraniol and farnesol. Although some common compounds existed in the two EOs, the same compounds were found in different contents. For example, the citronellol content increased by 31.90 % from 256,491.61 mg/kg to 338,314.45 mg/kg after salt treatment, while the geraniol content decreased by 16.34 % from 47,909.22 mg/kg to 40,080.63 mg/kg. The analysis of aroma showed that salt treatment did not have a strong influence on the aroma types of the EOs as seen from the similar aroma profiles between FERO and SERO, and the performance of antioxidant activities of SREO was superior to that of FREO.