Removal of aflatoxin B1 and inhibition of Aspergillus flavus growth by the use of Lactobacillus plantarum on olives.

Olives can be contaminated with a wide variety of molds (Aspergillus and/or Penicillium) that can be occurring naturally on fresh and processed olives and could support mycotoxin production. The aim of this work was to investigate aflatoxin B1 (AFB1) production by fungi and its bioaccumulation in olives during storage and to study the impact of the application of Lactobacillus plantarum on the inhibition of mold development and production of AFB1. Two different treatments were applied: (i) olives with natural microflora and (ii) olives inoculated with Aspergillus flavus after elimination of natural microflora. AFB1 has been extracted from olives and quantitated by high-performance liquid chromatography using a fluorescence detector. Results showed the absence of this metabolite in the olives for the season 2008 to 2009. In 2009 to 2010, AFB1 was detected at the level of 11 μg/kg. The application of L. plantarum during the storage of olives favors the reduction of the level of AFB1 to 5.9 μg/kg correlated with a decrease in the amount of molds (86.3%). The images obtained by environmental scanning electron microscopy showed that L. plantarum was able to adhere to the olive surface and probably produce a biofilm that inhibits the multiplication of yeast and fungi by oxygen competition. Results showed an increase of antioxidant activity and amount of total phenolic compounds of olives, respectively, by 24 and 8.6%. In many olives contaminated with A. flavus, AFB1 was present at an initial level of 5.15 μg/kg and increased to 6.55 μg/kg after 8 days of storage. The biological detoxification of AFB1 in olives by L. plantarum is confirmed by the reduction of the level of AFB1 to 2.12 μg/kg on day 0 and its absence after 4 days of storage.