Monitoring Lactic Acid Fermentation in Media Containing Dandelion (Taraxacum officinale) by FTIR Spectroscopy
Fourier-transform infrared (FTIR) spectroscopy is considered to be a comprehensive and sensitive method for detection of molecular changes in cells and media. In the present study, FTIR spectroscopy was employed as an easy, rapid and reliable technique to evaluate the lactic fermentation of Lactobacillus casei on a model de Man, Rogosa and Sharpe (MRS) medium with or without the addition of dandelion extract (DE). Dandelion, due to its high content in fructans, can be used as an additional carbon source in lactic fermentation. Lactic fermentation in a dandelion extract, using the FTIR fingerprint as a qualitative and semi-quantitative assay for lactic acid production was monitored. Specific bands of carbohydrates in the fingerprint region (1200-900 cm-1) and their shifts indicated the hydrolysis and metabolism during fermentation. The band at 1336 cm-1 may be considered a sensitive marker for the identification of L. casei during fermentation, while the dandelion extract showed a unique characteristic peak at 1436 cm-1. The results proved that the species were detectable and that significant spectral differences existed between fermented samples in media with or without dandelion addition. Representative peaks of bacteria and dandelion appeared in the spectra of a mixture of bacteria and dandelion. The peaks were evident in the samples taken using the model MRS media from the beginning of fermentation as opposed to at the end of fermentation.