Applicability of Lactobacillus plantarum IMDO 788 as a starter culture to control vegetable fermentations.

BACKGROUND: Fermentation of vegetables and fruits is a traditional preservation technique, e.g. in Eastern Europe. Although usually spontaneous fermentation processes are applied, the addition of lactic acid bacteria (LAB) starter cultures could accelerate processing and improve the consistency and quality of the end-products. RESULTS: The application of Lactobacillus plantarum IMDO 788 as a starter culture strain for cauliflower and mixed vegetable fermentations resulted in accelerated acidification as compared with the spontaneous fermentations. The strain dominated the background microbiota throughout the process, whereas the spontaneous fermentations were characterised by widely variable species diversity. During the spontaneous fermentations, almost all carbohydrates were converted into lactic acid, ethanol, mannitol and acetic acid, indicating the participation of both heterofermentative and homofermentative LAB species. During the starter culture-added fermentations, residual carbohydrates were found and lactic acid and ethanol were the main end-metabolites. Vegetable-associated aromas, ethyl acetate and isoamyl acetate were produced during all fermentations. The high concentration of ethanol and the production of ethyl acetate and isoamyl acetate suggested the involvement of yeasts during all fermentations. CONCLUSION: Lactobacillus plantarum IMDO 788 was an adequate starter culture strain for vegetable fermentations, prevailing over endogenous LAB communities. Further optimisation of the starter culture formulation is necessary to avoid yeast growth.

Antioxidant changes of leek (Allium ampeloprasum var. porrum) during spontaneous fermentation of the white shaft and green leaves.

BACKGROUND: Leek is grown for its thickened cylindrical white shaft made up of long leaf bases. Despite the potentially valuable nutritional profile of the green leaves, a large portion remains unused owing its restricted culinary applications. This large quantity of this plant biomass could be valorized given an adequate stabilization method. In this study, we examined leek fermentation with regard to antioxidant changes. RESULTS: The oxygen radical absorbance capacity (ORAC) increased by 62% when the green leaves were fermented for 21 days, while 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity did not increase significantly. Fermentation resulted in an increase of endogenous polyphenolic compounds such as ferulic acid, astragalin, luteolin and naringenin. Moreover, fermentation stimulated the production of a series of polyphenolic compounds that were not present in the fresh leek. The flavour precursors in leek, i.e. methiin and isoalliin, were reduced by 91-93% and 100%, respectively, when spontaneous fermentation was allowed to occur on the white shaft and green leaves. CONCLUSION: Our results demonstrated that application of fermentation resulted in a higher ORAC value and polyphenol content of the leek plant, especially in the green leaves. These results indicate the nutritional relevance of fermentation, which hold promise as a stabilization technique.

Bacterial community dynamics, lactic acid bacteria species diversity and metabolite kinetics of traditional Romanian vegetable fermentations.

BACKGROUND: Artisanal vegetable fermentations are very popular in Eastern European countries. Fresh vegetables undergo a spontaneous fermentation in the presence of salt, which is mainly carried out by lactic acid bacteria (LAB). RESULTS: Culture-dependent and culture-independent analyses of end-samples of various spontaneous vegetable fermentations carried out in houses of the Chiodju region (central Romania) revealed Lactobacillus plantarum and Lactobacillus brevis as the most frequently isolated LAB species. Leuconostoc mesenteroides and Leuconostoc citreum were also found. Furthermore, the community dynamics of spontaneous cauliflower and mixed-vegetable (green tomatoes, carrots and cauliflower) fermentations revealed three steps: an initial phase characterised by the presence of Enterobacteriaceae and a wide LAB species diversity, encompassing Weissella species; a second phase from day 3 onwards wherein L. citreum and Lb. brevis occurred; and a final phase characterised by the prevalence of Lb. brevis and Lb. plantarum. Metabolite target analysis revealed that glucose and fructose were mostly depleted at the end of fermentation. The main products of carbohydrate metabolism were lactic acid, acetic acid, ethanol and small amounts of mannitol, indicating heterolactate fermentation. CONCLUSION: Given their prevalence at the end of vegetable fermentations, Lb. brevis and Lb. plantarum appear to be good candidate starter cultures for controlled vegetable fermentation processes.