# Flavour Generation during Lactic Acid Fermentation of Brassica Vegetables--Literature Review
## 7 Brassica Fermented Products
### Sauerkraut
The partial squares-discriminant analysis (PLS-DA) revealed that compounds which contributed to the discrimination between the samples were ethyl hexadecanoate, hexyl acetate, neryl acetate, (_Z_)-3-octen-1-yl acetate, 1-pentanol, and 2-isothiocyanatobutane. The sensory analysis compared white colour, red colour, sulfur odour, fresh cabbage odour, fresh cabbage taste, hardness, crunchiness, juiciness, saltiness, sweetness, and overall quality, which were significantly different between the analyzed sauerkraut products. In general, the sensory properties of traditional cabbage cultivars were slightly better compared to commercially available sauerkraut products [69]. Studies by [PERSON] et al. [54; 103] evaluated the metabolic and microbial profile of northeast sauerkrauts, which are derived not from white cabbage (_Brassica oleracea_ L. var. _capitata_ L.) like European sauerkraut, but from Chinese cabbage (_Brassica rap_ L. _pekinensis_, cv. Wombok). In the first study [54], LAB were isolated from traditional northeast sauerkraut and single starter cultures were compared. In total, 99 volatile compounds, including 10 acids, 9 alcohols, 23 esters, 7 isothi cyanates, 13 aldehydes, 7 ketones, 2 hydrocarbons, 5 nitriles, 7 sulfides, 3 indoles, 9 terpen, and 4 lactones were tentatively identified at the end of fermentation. The greatest abundance of esters (ethyl lactate, ethyl acetate and isoamyl acetate) was detected in sauerkraut obtained after fermentation with _Lactobacillus plantarum_, while the highest level of lactones was observed in sauerkraut inoculated with _Lactobacillus paracasei_. In turn, the fermentation with _Leuconostoc mesenteroides_ and _Weissella cibaria_ resulted in the formation of acids and ketones [54]. The highest increase of free amino acids was observed in sauerkraut inoculated with _Lactobacillus paracasei_. In the second study by [PERSON] et al. [103], the sauerkrauts of different households were compared. In three different houses, the sampling was performed during the whole fermentation process. This time, 130 volatile compounds, including 11 acids, 16 alcohols, 24 esters, 22 aldehydes, 3 ketones, 6 nitriles, 5 isothi cyanates, 7 sulfides, 2 indoles, 5 hydrocarbons, 7 phenols, 6 lactones, and 16 terpen, were detected. The principal component analysis showed that at the beginning of the fermentation, the profile of volatiles was quite similar in all households. However, with the progress of the fermentation, the volatilomes separated, and three clusters for each house could be separated. The correlation analysis showed that the main bacteria detected in sauerkrauts, namely _Pseudomonas_, _Chloroplast_, _Rhizobium_, _Aureimonas_, _Sphingomonas_, _Lactobacillus_, _Leuconostoc_, _Enterobacter_, _Clostridium_ and _Weissella_, were statistically correlated with volatile compounds. At the same time, some negative correlations were observed, such as _Pseudomonas_, with 33 kinds of volatile compounds,including nitriles, _Chloroplast_ with 49 volatile compounds, including aldehydes, esters and nitriles, _Rhizobium_ with 36 volatile compounds, including lactones and aldehydes and others [103]. These observations can help to design the starter cultures for sauerkraut with certain, favourable properties. In the next study [30], the volatilome of northeast sauerkrauts fermented with mixed starter cultures was evaluated using knowledge about the LAB strains obtained before [103]. This time, except for the metabolomic profiling, the in-depth sensory characteristic with sensory panel, e-nose and e-tongue was performed. Chemometric analysis with clustering found 82 volatile compounds which were attributed to 11 classes, including 2 organic acids, 17 alcohols, 19 esters, 9 terpenes, 2 lactones, 9 aldehydes, 6 ketones, 8 sulfides, 4 isothiyanates, 3 polyphenols and 3 nitriles. All samples were clustered into five clusters according to the different stages of fermentation and type of mixed culture.