Study on the characteristics and differences in aroma components among different cultivars of Canarium album

Abstract: 【Objective】Fruit aroma is one of the determinants in fruit quality and flavor characteristics. Canarium album has gained the recognition from market with unique aroma. To explore the aroma profile characteristics of C. album, the volatile components of 11 varieties from different producing areas were analyzed in this study. Cluster analysis and orthogonal partial least squares discriminant analysis were used to classify volatile profile of 11 C. album varieties. The characteristic aromatic components detected in C. album were quantified using odor activity value (OAV), and the ratio of the volatile compound concentration to their odor threshold. Aroma components with an aroma value greater than or equal to 1 are considered as characteristic fragrances.【Methods】The volatile components in fruits of 11 varieties of C. album were analyzed by electronic nose combined with HS-SPME-GC-MS. The volatile compounds were determined according to mass spectrometry NIST 11.L and mass spectrometry library Wiley 7, and the CAS number of each volatile component was listed. Meanwhile, manual spectrogram analysis and data analysis were combined for qualitative analysis. The content of volatile components was determined by comparing with the peak area of internal standard. Fingerprint was made by Origin2018 software. Heatmap was made with TBtools. The variable importance in projection (VIP) was calculated by PCA and OPLS-DA (https://cloud.metware.cn). SPSS 19.0 software was used for single factor analysis. Results were extracted and visualized with Principal Component Analysis (PCA). 【Results】The results of electronic nose experiment showed that three sensors of orthogonal partial least squares discriminant analysis could distinguish different varieties of C. album, namely S1 sensor, S7 sensor and S8 sensor. S2 sensor had the highest response value among the 10 sensors and can reflect the aroma characteristics of C. album fruit, and the electronic nose experiment can distinguish 11 different varieties of C. album. The results of HS-SPME-GC-MS showed that the volatile components of C. album varieties were similar in 11 different varieties, but significantly different in contents. A total of 57 volatile components were detected in 11 different C. album varieties, which were analyzed by OPLS-DA and based on p- value<0.05, VIP≥1 condition, and 23 aroma substances were further screened out, which were related to C. album aroma quality, such as (-) -α-cubene, thymol, α-pinene and D-limonene contents, and the differences among 11 varieties reached a significant level. By comparing the OAV values of aroma substances of 11 varieties of C. album, the results showed that the OAV values of α-pinene in all varieties tested were higher, and the previous aroma description of α-pinene was mainly woody and pine-oil, so the olive fruits showed obvious woody and pine-oil aroma, which was woody flavor. Eleven different varieties of C. album can be divided into two categories. Among them, Pingyang No. 1, Pingyang No. 2, Lingfeng and Qinglan No. 1 showed significantly higher OAV values of α-pinene, caryophylene and β-pinene than other varieties, which showed significant pine oil fragrance and woody fragrance. Cinnamene, trans- 2- hexenal and D- limonene showed fruity, delicate and lemon aromas, but their aroma activity was significantly different compared with α-pinene, suggesting that these varieties were wood scented. In addition, the contents of aroma components of Pingyang No. 1 and Pingyang No. 3 were significantly higher than those of other varieties, so their aromatic flavor was stronger than that of other varieties. These results were generally consistent with the results of electronic nose experiment and OAV. Therefore, Pingyang No. 1 and Pingyang No. 3 were the cultivars with the most aromatic flavor of C. album fruits. It was believed that α-pinene, caryophyllene and β-pinene may be the key aroma compounds that form the aroma characteristics of C. album. Varieties like Sanlenlan and Meipu No. 2 displayed less significant pine incense and costus smell as their overall aroma active values were not significant, and anti-2- hexene aldehyde and myrcene contents in such varieties of aroma components were higher. These results suggested that their aromas were sweeter.【Conclusion】In this study, the aroma components affecting different C. album varieties were analyzed and compared, so as to provide theoretical reference for identifying different C. album varieties. Due to the influence of soil and microclimate, the aroma of fruits with the same variety may be different. Therefore, further research on the aroma of C. album fruits with the same variety in different habitats can be required by combining gas chromatography - time of flight mass spectrometry, mineral elements and gas chromatography-mass spectrum techniques to provide a new sight of aroma quality in C. album fruits in Fujian, Guangdong and Zhejiang. This study provides a new sight for understanding C. album aroma and flavor characteristics. Moreover, the genes related to the metabolism pathway of C. album terpene compounds should be excavated, the functional verification should be performed, and the mechanism of forming the flavor characteristics of C. album terpenes should be explored.