## 3 Results and Discussion
### Huanglongbing Effects on the Volatile Profile of 'Ray Ruby' Grapefruit juice  
A total of 87 volatiles were detected in HLB+ and HLB- 'Ray Ruby' grapefruit juice samples over two harvest seasons, and the components were classified into 12 chemical classes (Table 3 and Figure S2). In comparison to peel oil, the VOCs in the juice had a second major compound next to D-limonene, \(\beta\)-caryophyllene, a sesquiterpene hydrocarbon, and contained 12 more VOCs (a 16% increase), which were mostly low molecular weight aliphatic compounds (Tables 2 and 3). The most abundant chemical class was monoterrene hydrocarbons with 13 components representing 47% to 55% of the total volatiles (Table 3). The major monoterrene hydrocarbons were D-limonene followed by \(\beta\)-myrcene (Table 3). Unlike in the peel oil, they both increased in the juice of HLB+ fruit, as well as many other monoterrene compounds (Figure 5), although the differences were not significant. \(\beta\)-myrcene has a strong green and metallic odor, which may negatively affect the aroma and flavor characteristics of citrus and orange juices when present in high amounts [11; 40]. While sesquiterpene hydrocarbons constituted a small portion of the peel oil, 0.89-1.39% of total volatiles (Table 2), they were abundant in the juice, with relative abundances from 34 to 36% in 2020 and 31% in 2021 (Table 3). \(\beta\)-Caryophyllene has a woody-spicy, terpenic, sweet, and citrus flavor and is one of the key volatile components in grapefruit juice [41]. D-limonene and \(\beta\)-caryophyllene, the two major compounds in 'Ray Ruby' grapefruit juice volatiles, together accounted for nearly 70% of the total volatiles (Table 3). Both compounds decreased in HLB+ fruit in both harvest seasons (Figure 5). Limonene and \(\beta\)-caryophyllene are reported to decrease in juice as the fruit matures [42]. This could be the explanation for the higher concentration of these volatiles in HLB+ juice, considering the slow maturation of HLB+ fruits, which are usually similar to immature fruit [9]. These terpene hydrocarbons have chemo-preventative functions, such as induction of glutathione-S-transferase activity and uridine diphosphoglucuronosyl transferase activity in the small intestine and liver [42; 43]. D-limonene also has chemotherapeutic activity against pancreatic, mammary, and prostatic tumors [44] and helps to prevent the initiation and suppress the progression of mammary and liver cancer [45]. Like in peel oil, nootkatone was significantly decreased in HLB+ fruit juice (Table 3, Figures 5 and 6). Nootkatone concentration is considered the grapefruit juice quality indicator [33; 34; 39], and HLB negatively affected the juice flavor quality (Table 3, Figures 5 and 6). C8-C10 aldehydes were significantly lower in HLB+ fruit juice than in HLB\(-\) juice (Table 3, Figures 5 and 6). These long-chain aldehydes and nootkatone are critical for high-quality grapefruit juice [36; 42]. The results confirmed that HLB negatively affected the juice flavor quality (Table 3, Figures 5 and 6). The CA divided the compounds into four groups: group I with 48 out of 87 compounds decreased by HLB; group II with 10 compounds decreased by HLB in 2020 but increased by HLB in 2021; group III composed of 8 compounds increased by HLB in 2020 but decreased in 2021; and group IV with 21 compounds increased by HLB, including acetaldehyde, ethanol, and ethyl acetate (Figure 5). Contrary to peel oil, in which more VOCs were increased by HLB, more VOCs were decreased in HLB+ juice (48 decreases-21 increases, Figure 5). \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Feak No.