Comparison of the antifungal effect of undissociated lactic and acetic acid in sourdough bread and in chemically acidified wheat bread

Els Debonne; Fien Van Schoors; Peter Maene; Filip Van Bockstaele; Pieter Vermeir; Jan Verwaeren; Mia Eeckhout; Frank Devlieghere

doi:10.1016/j.ijfoodmicro.2020.108551

Comparison of the antifungal effect of undissociated lactic and acetic acid in sourdough bread and in chemically acidified wheat bread

Int J Food Microbiol. 2020 May 16:321:108551. doi: 10.1016/j.ijfoodmicro.2020.108551. Epub 2020 Feb 8.

Authors

Els Debonne¹, Fien Van Schoors², Peter Maene³, Filip Van Bockstaele⁴, Pieter Vermeir³, Jan Verwaeren⁵, Mia Eeckhout⁶, Frank Devlieghere⁷

Affiliations

¹ Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Laboratory of Applied Mycology (MYCOLAB), Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium. Electronic address: [email protected].
² Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium.
³ Laboratory for Chemical Analysis (LCA), Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium.
⁴ Laboratory of Food Technology and Engineering, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
⁵ Department of Data Analysis and Mathematical Modelling, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
⁶ Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Laboratory of Applied Mycology (MYCOLAB), Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium.
⁷ Laboratory of Applied Mycology (MYCOLAB), Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Research Unit Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.

PMID: 32078867
DOI: 10.1016/j.ijfoodmicro.2020.108551

Abstract

Sourdough is a very interesting natural preservation system to prolong mould free shelf-life of bread. Numerous studies have reported that the antifungal activity of sourdough is mainly correlated with the presence of lactic (LA) and acetic acid (AA), but very few information is available on the effect of undissociated acid concentrations in the aqueous phase of bread (C_HA; mmole/L). This study was conducted to provide additional information about the mode of action of the acids in sourdough bread, enabling a better shelf-life prediction. This study was divided into two parts. In part 1, three industrial biological sourdoughs were characterized (dough yield, pH, a_w, fermentation quotient, microbiota). During 7 weeks, a shelf-life test with natural flora was conducted with daily checks of visible mould growth (21 °C). In part 2, the effect of the acids present in the antifungal active sourdough breads was validated in chemically acidified wheat breads. Complete growth inhibition was observed in full-baked sourdough bread (30 g/100 g dough) containing Lactobacillus sanfranciscensis and Saccharomyces cerevisiae as dominant sourdough micro-organisms, whereas in control bread the shelf-life was limited to 4.4-9.2 days. These full-baked sourdough breads contained 36 mmole undissociated LA/L and 220 mmole undissociated AA/L. The data were used to make General Linear Regression models for shelf-life prediction and resulted in a fit of R² = 0.79 when expressing the shelf-life in function of C_HA,LA and C_HA,AA. In acidified breads, the role of lactic acid was not significant and only impacted shelf-life indirectly through acidification. No difference between antifungal activity of sourdough breads and chemically acidified bread with comparable C_HA,AA concentrations was observed. Shelf-life increased when 150-200 mmole undissociated AA/L aqueous phase in bread was present. To conclude, this study showed the importance of the undissociated acid fraction of acetic acid in relation to bread shelf-life, together with bread pH and moisture content.

Keywords: Acetic acid; Bread; Shelf-life; Sourdough; Undissociated acid.

Publication types

Comparative Study

MeSH terms

Acetic Acid / analysis
Acetic Acid / pharmacology*
Antifungal Agents / analysis
Antifungal Agents / pharmacology*
Bread / analysis*
Bread / microbiology
Fermentation
Food Preservation / methods*
Fungi / drug effects
Fungi / growth & development
Lactic Acid / analysis
Lactic Acid / pharmacology*
Lactobacillus / drug effects
Lactobacillus / growth & development
Triticum / microbiology
Water / analysis

Substances

Antifungal Agents
Water
Lactic Acid
Acetic Acid