Abstract
The lactic acid bacteria are key microorganisms for the production and preservation of fermented dairy products, cheeses, sourdough bread, and lacto-fermented vegetables. This study was developed to monitor lactic acid produced by Lactobacillus plantarum ATCC 8014 and Lactobacillus casei ATCC 393, as single strains and combined, in fermenting media by Fourier Transform Infrared Spectroscopy coupled to multivariate statistical analysis. Media containing different mixtures of carbohydrates were chosen as model fermenting media for monitoring lactic acid concentration by infrared spectroscopy, due to the fact that vegetable and animal food matrices could contain different carbohydrates as carbon sources. Three different types of media were obtained by adding different carbohydrates to a basic MRS medium. HPLC was used as reference method for lactic acid quantification. The calibration set (n=36) was used for building model, while a validation set (n=13) for testing the robustness of the developed model. The coefficients of determination between predicted and reference values were 0.986 and 0.965, while root mean square error for calibration and validation sets recorded values of 0.127 and 0.263 g·l−1, respectively. Results confirmed the efficiency of FTIR spectroscopy combined with multivariate statistics, as a rapid, reliable, and cost-effective tool for routine monitoring of lactic acid.
Highlights
The lactic acid bacteria are key microorganisms for the production and preservation of fermented dairy products, cheeses, sourdough bread, and lacto-fermented vegetables
High-performance liquid chromatography (HPLC) has been the commonly accepted technique used in organic acid determination (SIVAKESAVA et al, 2001; MOREIRA & SANTOS, 2005; LIU et al, 2011)
Fourier-transform infrared (FTIR) analysis coupled with data-processing algorithms has become a powerful tool (MOREIRA & SANTOS, 2005)
Summary
The lactic acid bacteria are key microorganisms for the production and preservation of fermented dairy products, cheeses, sourdough bread, and lacto-fermented vegetables. Quantitative infrared spectroscopy has been used for monitoring glucose and gluconic acids (FRANCO et al, 2006) or for lactic acid production from whey (TRIPATHI et al, 2015), for organic acids determination in fruit vinegars (LIU et al, 2011), wine (REGMI et al, 2012; MARTELO-VIDAL & VÁZQUEZ, 2014a), fruit (BUREAU et al, 2009), and tomatoes (BEULLENS et al, 2009), as well as for detection of polyphenolic compounds from red wine (MARTELO-VIDAL & VÁZQUEZ, 2014b) and nutritional compounds determination from yogurt (MOROS et al, 2006) and cheese (SUBRAMANIAN et al, 2011) Most of these quantitative determinations were validated by multivariate statistics or chemometrics. The main objective of our study was to develop a rapid and simple FTIR method and a calibration model to monitor lactic acid concentrations during lactic acid fermentation by Lactobacillus plantarum ATCC 8014 and Lactobacillus casei ATCC 393 in model fermentation media containing different carbohydrates
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