Piperaceae extracts for controlling Alicyclobacillus acidoterrestris growth in commercial orange juice

The present study aimed evaluate the antibacterial effect of Piper peltatum and Piper marginatum extracts against Alicyclobacillus acidoterrestris using the microdilution method. P. marginatum achieved a minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) of 62.50 mu g/mL while P. peltatum obtained a MIC/MBC of 15.62 mu g/mL, and was therefore selected for fractionation. Six fractions were obtained and tested. The hexane-dichloromethane fraction achieved the lowest MIC/MBC of 31.25 mu g/mL and was fractionated, isolating the 4-Nerolidylcatechol compound (4-NC). The checkerboard method produced a synergistic effect between nisin and the crude extracts and the fraction, and an additive effect in relation to the 4-NC isolate. The application of the extracts, fraction and isolate in reconstituted orange juice previously inoculated with A. acidoterrestris proved effective as an antibacterial agent after 24 h of incubation and reduced the initial microbial population. The dose-response effect and cell viability, measured through the selectivity index, obtained values greater than 1.0, showing that the extracts were more selective for the microorganism and less toxic for the LLCM-K2 cells. Scanning electron microscopy identified changes in the membrane of the vegetative and spore cells of A. acidoterrestris when treated with this compound. The present study demonstrated the antibacterial efficacy of Piperaceae extracts and nisin against A. acidoterrestris in orange (Citrus sinensis) juice, which can therefore be considered to have major potential for application in the food industry.