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Antifungal activity of phenyllactic acid against molds isolated from bakery products
Paola Lavermicocca1, Francesca Valerio, Angelo Visconti
1Institute of Sciences of Food Production, National Research Council (CNR), 70125 Bari, Italy. p.lavermicocca@area.ba.cnr.it
Abstract:
Phenyllactic acid (PLA) has recently been found in cultures of Lactobacillus plantarum that show antifungal activity in sourdough breads. The fungicidal activity of PLA and growth inhibition by PLA were evaluated by using a microdilution test and 23 fungal strains belonging to 14 species of Aspergillus, Penicillium, and Fusarium that were isolated from bakery products, flours, or cereals. Less than 7.5 mg of PLA ml(-1) was required to obtain 90% growth inhibition for all strains, while fungicidal activity against 19 strains was shown by PLA at levels of < or = 10 mg ml(-1). Levels of growth inhibition of 50 to 92.4% were observed for all fungal strains after incubation for 3 days in the presence of 7.5 mg of PLA ml(-1) in buffered medium at pH 4, which is a condition more similar to those in real food systems. Under these experimental conditions PLA caused an unpredictable delaying effect that was more than 2 days long for 12 strains, including some mycotoxigenic strains of Penicillium verrucosum and Penicillium citrinum and a strain of Penicillium roqueforti (the most widespread contaminant of bakery products); a growth delay of about 2 days was observed for seven other strains. The effect of pH on the inhibitory activity of PLA and the combined effects of the major organic acids produced by lactic acid bacteria isolated from sourdough bread (PLA, lactic acid, and acetic acid) were also investigated. The ability of PLA to act as a fungicide and delay the growth of a variety of fungal contaminants provides new perspectives for possibly using this natural antimicrobial compound to control fungal contaminants and extend the shelf lives of foods and/or feedstuffs.
Insights
Phenyllactic acid (PLA), found in sourdough, effectively inhibits and kills common food spoilage fungi. This natural antimicrobial shows promise for extending food shelf life by controlling fungal contamination.
Area of Science:
- Food Microbiology
- Natural Antimicrobials
- Food Preservation
Background:
- Lactobacillus plantarum in sourdough exhibits antifungal properties.
- Phenyllactic acid (PLA) is identified as a key antifungal compound.
- Food spoilage fungi pose significant challenges in bakery products, flours, and cereals.
Purpose of the Study:
- To evaluate the fungicidal and growth inhibitory activity of phenyllactic acid (PLA).
- To assess PLA's efficacy against a broad spectrum of fungal contaminants.
- To investigate the influence of pH and combined organic acids on PLA's activity.
Main Methods:
- Microdilution tests were performed using 23 fungal strains (Aspergillus, Penicillium, Fusarium).
- Antifungal activity was assessed at various PLA concentrations and pH 4.
- Combined effects of PLA, lactic acid, and acetic acid were investigated.
Main Results:
- PLA achieved 90% growth inhibition for all tested fungi at <7.5 mg/ml.
- Fungicidal activity was observed against 19 strains at <=10 mg/ml.
- PLA demonstrated significant growth delay (>2 days) for 12 strains, including mycotoxigenic species, at pH 4.
Conclusions:
- Phenyllactic acid exhibits potent fungicidal and growth-inhibiting properties against food spoilage fungi.
- PLA shows potential as a natural antimicrobial agent for food preservation.
- Controlling fungal contaminants and extending food shelf life are key applications for PLA.