Abstract
Preventing food spoilage without the addition of chemical food additives, while increasing functional properties of wheat-based bakery products, is an increasing demand by the consumers and a challenge for the food industry. Within this study, lactic acid bacteria (LAB) isolated from sourdough were screened in vitro for the ability to utilize the typical wheat carbohydrates, for their antimicrobial and functional properties. The dual culture overlay assay revealed varying levels of inhibition against the examined fungi, with Lactiplantibacillus plantarum S4.2 and Lentilactobacillus parabuchneri S2.9 exhibiting the highest suppression against the indicator strains Fusarium graminearum MUCL43764, Aspergillus fumigatus, A. flavus MUCL11945, A. brasiliensis DSM1988, and Penicillium roqueforti DSM1079. Furthermore, the antifungal activity was shown to be attributed mainly to the activity of acids produced by LAB. The antibacillus activity was evaluated by the spot-on-the-lawn method revealing a high inhibition potential of the majority of LAB isolated from sourdough against Bacillus cereus DSM31, B. licheniformis DSM13, B. subtilis LMG7135, and B. subtilis S15.20. Furthermore, evaluating the presence of the glutamate decarboxylase gen in LAB isolates by means of PCR showed a strain dependency of a potential GABA production. Finally, due to improved functional activities, LAB isolated from sourdoughs exhibit promising characteristics for the application as natural preservatives in wheat-based bakery products.
Highlights
Within the last years, the importance of the new term “clean label” has increased due to a rising awareness of the consumer regarding healthiness and sustainability of food products [1]
The dual culture overlay assay revealed varying levels of inhibition against the examined fungi, with Lactiplantibacillus plantarum S4.2 and Lentilactobacillus parabuchneri S2.9 exhibiting the highest suppression against the indicator strains Fusarium graminearum MUCL43764, Aspergillus fumigatus, A. flavus MUCL11945, A. brasiliensis DSM1988, and Penicillium roqueforti DSM1079
The antibacillus activity was evaluated by the spot-on-the-lawn method revealing a high inhibition potential of the majority of lactic acid bacteria (LAB) isolated from sourdough against Bacillus cereus DSM31, B. licheniformis DSM13, B. subtilis LMG7135, and B. subtilis S15.20
Summary
The importance of the new term “clean label” has increased due to a rising awareness of the consumer regarding healthiness and sustainability of food products [1]. Fermentation processing is one of the oldest technologies applied and is an effective way for bio-preservation, leading to improved sensory and nutritional qualities, and an increased microbiological safety and shelf life [2]. These reasons led to a regained momentum of sourdough products within the last years [3]. The preservative effect obtained by the application of sourdough is mainly due to the production of lactic and acetic acids, which leads to a drop of the pH, with a stable sourdough exhibiting pH values of approximately 3.5 to 4.0 [6]. The contaminants mainly derive from the baking environment, flour, yeast, or further ingredients [9,16] and exhibit suitable growth conditions within the bread regarding the water activity (aw) and pH [17]
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