Researchers from the Laboratory of Food Chemistry and Toxicology at the University of Valencia found that some strains of lactic acid bacteria (LAB) can inhibit fungal growth and reduce the presence of toxins in bread.
They conducted a study to: evaluate the antifungal activity of LAB against Aspergillus parasiticus and Penicillium expansum; estimate the shelf-life of breads fermented with yeast and LAB; and analyze the reduction of aflatoxin content in bread inoculated with A. parasiticus.
In the study, which was published in the journal Food Control, 16 strains of LAB were cultivated and their antifungal activity against A. parasiticus and P. expansum tested.
Researchers then used those LABs that had shown antifungal activity in bread fermentation with yeast to study fungal growth inhibition and aflatoxin reduction in processed bread previously inoculated with A. parasiticus.
The bread recipe included 400g of wheat flour, 3g of sucrose, 6g of salt, 20g of yeast and 500 ml of tap water. The probiotic bacteria were added during the baking process.
Six bacteria strains - Lactobacillus bulgaricus, L. plantarum, L. johnsoni, L. rhamnosus (CECT 288), L. ruminis and Bifidobacterium bifidum were used in the bread study against a control loaf fermented only with yeast.
Fungal growth was seen on the control loaf and loaves containing four of the bacteria strains on the fifth day of incubation.
Improvement in shelf life
Two strains of bacteria - L. bulgaricus and L. plantarum – showed an improvement in shelf life, however. Fungal growth was not seen on loaf breads fermented with L. bulgaricus until the eighth day, and was not seen on those containing L. plantarum until the ninth day.
Across the six strains tested in bread, analysis of samples by liquid chromatography and mass spectrometry showed a reduction in aflatoxin content ranging from 84.1% to 99.9%.
“The present results suggest that metabolism products of LAB, due to their potential to reduce the growth of the mycotoxigenic fungi and the biosynthesis of the mycotoxins, could be promising for the bioconservation of packaged food such as loaf bread,” states the study.
The research was supported by the Ministry of Economy and Competitiveness and by the Santiago Grisolia pre-PhD program of University of Valencia.
Source: Food control
Published online ahead of print: http://dx.doi.org/10.1016/j.foodcont.2016.03.012
“In vitro antifungal activity of lactic acid bacteria against mycotoxigenic fungi and their application in loaf bread shelf life improvement”
Authors: Federica Saladino; Carlos Luz; Lara Manyes; Mónica Fernández-Franzón; Giuseppe Meca