# Aroma Volatiles in Litchi Fruit: A Mini-Review
## 2 The Profiles of VOCs in Litchi Fruit  
Over the past four decades, the VOCs in 25 litchi cultivars were detected using different techniques. Here, in order to more clearly illustrate the VOC profiles among these litchi cultivars, we summarized and integrated the results from 20 references available, including the production area, detection method, and total number of VOCs in a specific cultivar. As shown in Table 1, there were two studies from the United States of America. [PERSON] et al. [22] first identified 42 VOCs from an unknown cultivar of litchi obtained from the Florida ychee growers association and believed that \(\beta\)-phenethyl alcohol, its derivatives, and terpenoids comprised the major portion of the VOCs in litchi fruit. A total of 31 VOCs were detected in \"sweetheart\" litchi fruit by [PERSON] et al. [23], among which metholand and geraniol exhibited the highest flavor dilution factors (FDs) through aroma extract dilution analysis, indicating that these two VOCs were probably the most important characteristic aromas. The VOC compositions of 18 Chinese varieties were determined with GC-MS. According to the results from 15 references, the number of VOCs varied greatly, ranging from 22 (\"Gualv\" (GL)) to 173 (\"Huaizhi\" (HZ)). Generally, the more studies carried out, the more VOCs that were detected in a specific cultivar. Five studies analyzed the VOCs in HZ and \"Heye\" (HY). Rose oxide, 1-octen-3-ol, linalool, geraniol, and geraniol were considered the main aroma compositions of HZ fruit by [PERSON] et al. [24]. However, this conclusion was different from those of [PERSON] et al. [25] and [PERSON] et al. [26], who found that anisyl alcohol, benzyl alcohol, germacrene D, \(\beta\)-myrcene, and methyl benzoate contributed to a large proportion of the aroma of HZ fruit. There were 161 VOCs identified in HY fruit. [PERSON] [27] showed that rose oxide had the highest odorant activity value (OAV) at 1223.3, implying that it might play a dominant role in determining the aroma of HY fruit. Six studies analyzed the VOCs in \"Nuomici\" (NMC), and a total of 143 VOCs were detected in NMC fruit, among which geraniol, guaiaiocl, vanillin, 2-acetyl-2-thiazoline, 2-phenylethanol, (Z)-2-nonenal, \(\alpha\)-damascenone, 1-octen-3-ol, furaneol, and linalool were found to be the most odor-active [32]. Interestingly, three studies [29; 30; 31] found that the contents of \(\alpha\)-selineine and limonene were relatively higher than other VOCs, suggesting that these two compounds also contribute more to the aroma in NMC fruit. \"Guiwei\" (GW) had 114 VOCs in total, and rose oxide, geraniol, and linalool had high OVA values, which had decisive effects on the aroma [27]. In addition, [PERSON] et al. [28] found that the content of \(\alpha\)-pinene was also higher in GW fruit. A total of 111 VOCs were detected in \"Baila\" (BL), and the relative content of hexanal, (E)-2-hexanal, farnesol, terpinolene, geraniol, and \(\beta\)-citronello! were high in the volatile profiles [24; 32; 33]. A total of 104 VOCs were detected in \"Feizixiao\" (FZX), and _cis_-rose oxide and 1-octen-3-ol were the most potent odorants for OAVs [24], and nerol and _cis_-pinene had a higher share in terms of relative content [28; 30]. \"Yuhebao\" (YHB) had 48 VOCs in total; 1-methoxy-2-propanol, acetoin, \(\beta\)-pinene, terpinolene, limonene, and nerol were thought to have an important effect on the aroma due to their relatively higher content [28; 30]. \"Guanyinlv\" (GYL) fruit had 62 VOCs, among which limonene, terpinolene, myrcene, ethyl acetate, prenylacetate, nerol, isoprenol, and 1-octen-3-ol were the primary components in the aroma compositions [35]. \"Bingli\" (BL2) produced 63 VOCs, among which hexanal, 6-methyl-5-hepten-2-one, limonene, and \(\alpha\)-muurolene were the major constituents for the characteristic aroma [36]. \"Lingfengnuo\" (LFN) had 41 VOCs, and myrcene, 2-carene, and limonene exhibited high relative content [26].