Aroma Quality Analysis of Guangdongxiangshui Lemon Based on Molecular Sensory Technology

Tea drinks made from Guangdongxiangshui lemon is popular among consumers, but its aroma profile, main aroma-active compounds and corresponding key biosynthesis genes still need to be analyzed. In this study, integrated molecular sensory technology including metabolomics and sensory evaluation was used to explore the material basis and corresponding key genes for the aroma quality of Guangdongxiangshui lemon, aiming at laying a foundation of the citrus aroma quality.

The volatiles of Guangdongxiangshui lemon from three areas, including Weishan, Yunfu and Wuzhou, were detected via GC-MS, and the aroma quality were evaluated by sensory evaluation panels. The aroma active compounds of Guangdongxiangshui lemon were identified by GC/O-MS combined with aroma extract dilution analysis (AEDA), aroma activity value (OAV) analysis and aroma recombination experiment, and then the characteristic aroma compounds were further identified. Based on gene family analysis, the genes related to aroma formation were illustrated.

A total of 40, 21 and 33 volatiles were identified in the flavedo, pulp and slices of Guangdongxiangshui lemon, respectively. The samples with the highest volatile content in flavedo and pulp tissues were from Weishan and Yunfu, respectively. In terms of aroma attributes, the aroma intensity of Guangdongxiangshui lemon slices from Weishan and Yunfu was significantly higher than that of Wuzhou. The whole fruit aroma quality of samples from Wuzhou was better than that of samples from other origins. Solvent-assisted flavor evaporation (SAFE) and other methods were used to extract the essential oil of Guangdongxiangshui lemon in Weishan, and 25 aroma active compounds were identified. Combined with OAV analysis and aroma recombination experiments, citronellal and citral were further identified as its characteristic aroma compounds, and the aroma flavor wheel was further constructed. Based on the conserved domain and Blast comparison, 52 terpene synthase (TPS) genes were identified in Guangdongxiangshui lemon genome, which might be involved in the aroma compounds synthesis.

The volatile spectrum and sensory evaluation showed that the aroma quality of Guangdongxiangshui lemon slices from Weishan were outstanding. A total of 25 aroma active compounds were identified. Among them, citronellal and citral were the characteristic aroma compounds of Guangdongxiangshui lemon, while d-limonene provided a background aroma. Combined with quantitative descriptive analysis and odor note collected via GC/O-MS, the aroma wheel of Guangdongxiangshui lemon was constructed with 15 aroma descriptors in 6 categories, including ‘fruity’ ‘woody’ ‘medicinal’ ‘spicy’ ‘floral’ and ‘grassy’. Furthermore, 52 TPS genes were mined in Guangdongxiangshui lemon genome, which might participate in the aroma compounds synthesis.