# Flavour Volatiles of Fermented Vegetable and Fruit Substrates: A Review
## 3 Results
### Terpenes and Norisoprenoids
plantarum_, the \(\upalpha\)-terpineol concentration was 84.2, 154.9, and 151.1 ng/mL, respectively, where it was not detected in the unfermented juice, and in addition, the \(\upalpha\)-terpineol was not detected in the unfermented Xuxiang cultivar juices [49]; (3) in goji juice fermented by a bacterial mixture (_L. rhamns_, _L. reuteri_, and _B. velezensis_), the \(\upalpha\)-terpineol concentration was 38.7 ng/g, compared to 33.9 ng/g in the unfermented juice [25]; (4) in non-pH-adjusted (2.65) bog bilberry juice fermented by two strains of _L. plantarum_, the \(\upalpha\)-terpineol concentration was 5.2 and 5.9 ng/mL, compared to 4.3 ng/mL in the unfermented juice, where the pH of the juice was adjusted to pH 3.5, the initial \(\upalpha\)-terpineol concentration was 3 ng/mL, which was reduced after fermentation by two strains of _L. plantarum_ to 2.8 and 2.5 ng/mL [34]; and (5) in mango slurry fermented by different LAB, \(\upalpha\)-terpineol was detected, where it was not detected after yeast fermentation or in the unfermented mango slurry [41]. \(\beta\)-damascenone, another important flavour terpene compound, was detected after fermentation in 4 studies: (1) In Hetai varietal juibe juice fermented by either _L. acidophilus_, _L. casei_, _L. helveticus_, or _L. plantarum_, the \(\beta\)-damascenone concentration was 16.7, 22.4, 19.0, and 21.4 ug/mL, respectively, where it was not detected in the unfermented juice [20]; (2) the \(\beta\)-damascenone concentration in a distillate prepared using simple distillation from a melon by-product fermented by _L. rhamnus_ was 8 ug/mL, compared to 1.2 ug/mL in the unfermented melon by-product distillate, and when using vacuum distillation, the \(\beta\)-damascenone concentration was 0.03 ug/mL in unfermented melon by-product distillate and 0.12 ug/mL in the distillate of _L. rhamnus_ fermented melon by-product [44]; (3) in goji juice fermented by different combinations of mixed bacterial cultures, the \(\beta\)-damascenone concentration ranged from 39.6 to 52 ng/g, where it was not detected in the unfermented juice [25]; and (4) in apple juice fermented by different LAB, the \(\beta\)-damascenone concentration ranged from 2.4 to 3.9 ng/mL, where it was not detected in the unfermented juice [19]. However, [PERSON] et al. [21] reported in apple juice that the initial \(\beta\)-damascenone concentration was 12.8 ng/g and that after fermentation with LAB, it was not detected. Eugenol is a volatile phenol that imparts clove, honey, and spicy notes to fermented fruit and vegetable juices. In the three papers, where it was mentioned, it was classified as a terpene: (1) In horse gram sprouts fermented by two _L. plantarum_ strains, the eugenol concentration was 5.2 and 5.3 ug/g, and it was not detected in raw seeds [37]; (2) in cherry juice fermented by either _L. paracasi_ or _L. rhamnus_, the eugenol concentration was 3.9, and 26.8 ng/mL, respectively, compared to 2.4 ng/mL in the unfermented juice, and cherry juice fermented by four _L. plantarum_ strains, the eugenol concentration was 11.1, 13.0, 14.7, and 22.4 ng/mL, compared to 3.2 ng/mL in the unfermented juice [29]; and (3) in apple juice fermented by either _L. plantarum_, _L. rhamnus_, _L. casei_, or _L. acidophilus_, the eugenol concentration was 9.1, 6.2, 17.1, and 33.3 ng/g, respectively, compared to 5.4 ng/g in the unfermented juice [21]. In addition, geranoid was detected in 3 studies after fermentation: (1) In watermelon juice fermented by either _L. plantarum_, _L. brevis_, _P. pentosacus_, _L. casei_, or _L. rhamnus_, the geranoid concentration was 5.6, 1.7, 1.7, 1.5, and 1.3 ng/mL, respectively, compared to 1.0 ng/mL in the unfermented juice [48]; (2) in goji juice fermented by bacterial mixture, the geranoid concentration ranged from 119.3-246 ng/g, where it was not detected in the unfermented juice [25]; and (3) in apple juice fermented by either _L. plantarum_, _L. rhamnus_, _L. casei_, or _L.