Microbiota and Quality Indexes of Commercial Sauerkraut and Fermented Cucumbers

Sauerkraut and fermented cucumbers are the most commonly consumed fermented vegetables in several regions of Eastern, Central, and Western Europe; thus, their quality is of great importance. In this study, the quality and bacterial microbiota of commercial samples of fermented cucumbers and sauerkraut were assessed. The identification and quantification of the microbial consortia were performed using nanopore sequencing, and ultrahigh-performance liquid chromatography-tandem mass spectrometry was used to analyse the content of biogenic amines. The physicochemical analysis showed great sample differentiation. Microbial analysis revealed a large diversity of types and relative abundances amongst the studied samples. Lactobacillaceae dominated the microbial community of fermented products, with the most common genera being Latilactobacillus, Leuconostoc, Lactiplantibacillus, Levilactobacillus, Lentilactobacillus, Secundilactobacillus, and Pediococcus. As for biogenic amines, putrescine prevailed both in the samples of fermented cucumber and sauerkraut, followed by cadaverine. The calculated biogenic amine index for four samples of sauerkraut and one of pickled cucumbers exceeded the estimated upper toxicity limit, ranging from 392 to 541, respectively. Spearman correlation analysis showed a significant positive correlation between Secundilactobacillus and cadaverine content in sauerkraut samples and between Levilactobacillus and Secundilactobacillus and cadaverine and histamine content in fermented cucumbers.