Abstract The aim of this study was to evaluate the capacity of two strains of lactic acid bacteria (LAB), Lactobacillus rhamnosus and Lactococcus lactis, and a yeast strain, Saccharomyces cerevisiae, inactivated by heat (121 °C, 10 min), from binding to aflatoxin M1 (AFM1), as well as the interaction between these microorganisms, aflatoxin M1 and the Minas Frescal cheese matrix after 2 and 30 days of storage. The ability of LABs and S. cerevisiae to bind AFM1 to Minas Frescal cheese was evaluated by high performance liquid chromatography (HPLC) composed of a fluorescence detector. The interaction between these microorganisms and AFM1 was evaluated using a scanning electron microscope composed of a backscattered electron detector with a voltage of 15 kV and magnifications of 1000 ×, 5000 × and 8000 ×. The use of microorganisms as a biological method is efficient in reducing AFM1 in Minas Frescal cheese and does not affect the microbiological parameters. AFM1 reduction varied according to the microorganism used in the treatments. S cerevisiae showed greater capacity to bind AFM1 over time, compared to LABs. Scanning electron microscopy was especially useful, confirming that lactic acid bacteria and S. cerevisae were able to bind AFM1 particles in Minas Frescal cheese.

Abstract Dairy cattle when fed on aflatoxin B1 may excrete aflatoxin M1 in milk as a consequence of dietary exposure. Once AFM1 is excreted in milk, it is present in dairy products such as cheese, yogurt, among others. This mycotoxin is quite resistant to temperature therefore heat treatments like pasteurization and ultra-pasteurization are not enough to inactivate it. In this context, this article provides an overview of the biological decontamination methods on milk and cheese of the last decade, as a contribution to evaluate the evolution of this strategy as well as its efficiency according to their authors. Relevant studies published between January 2009 and May 2019 were selected after a systematic search of the literature in PubMed, Science direct and Google Scholar databases. According with our research in the last decade few studies have been published on these methods and unfortunately none of the published studies tested such methods in cheese. Throughout the research many studies on decontamination methods were found, however, in phosphate buffered saline solution or in culture medium. Further studies on biological decontamination on milk and mainly on cheese are necessary for this technique to be better developed and applied to a large scale in the industries.

ABSTRACT This study aimed to investigate the effect of peracetic acid (PAA, 0.5%) on adherent cells of three strains of Listeria monocytogenes strains belonging to serotypes 4b and 1/2b that had been previously isolated from the environment of a Brazilian cheese plant. The assays were conducted using polystyrene microplates and stainless steel coupons and the adhered cells were treated with PAA for 60, 120 and 180 s. On stainless steel, biofilms were partially inactivated by PAA after 60 s and almost 100% of the cells were damaged within 180 s using epifluorescence microscopy with LIVE/DEAD® staining. On polystyrene microplates, PAA decreased (P<0.05) biofilm biomass produced by the three L. monocytogenes isolates at 60 s, when compared with controls (no PAA treatment). However, PAA did not completely eliminate L. monocytogenes cells on polystyrene microplates (decreasing 1.8-2.5 log cycles after treatment with PAA for 180 s). The correct concentration and contact time of PAA is critical for eliminating biofilms formed by L. monocytogenes on stainless steel surfaces, although further studies are needed for defining efficient PAA treatments to remove adherent cells of this pathogen on plastic polymers.

We evaluated the frequency of enterococci from food and found 95.2% of positivity, being E. faecium and E. faecalis the most frequent species. High-level streptomycin resistance was observed, as well as gelatinase and hemolysis activity, showing the potential role of environmental strains as reservoir of virulence and resistance traits.