The antifungal effects of cinnamaldehyde against Aspergillus niger and its application in bread preservation

Cinnamaldehyde (CIN) is a promising replacement for chemical synthetic preservatives, which has exhibited effective antimicrobial activities in food applications. In this study we examined the antifungal efficiency of CIN against Aspergillus niger in vitro. In addition, we explored its mode of action and evaluated its application potential in bread preservation in situ. The results showed that CIN exerted different levels of antifungal activity through different treatments, wherein it showed the highest antifungal activity in the liquid broth test, followed by solid contact and gas diffusion methods. On the other hand, ultrastructure observation, propyl iodide staining and ergosterol detection showed that CIN may damage the cell ultrastructure and membrane integrity in a dose dependent manner. Besides, the content of reactive oxygen species and malondialdehyde were, respectively, 2.74 and 2.07 times higher in fungi treated with 100 μg/mL of CIN, compared with those in untreated fungi. Finally, shelf life experiment showed that, in the vapor phase, CIN can efficiently prolong the shelf life of bread. Altogether, these results indicate that CIN can be used as an alternative food preservative due to its antifungal effects that are exerted, at least in part in A. niger, through the induction of oxidative stress, which caused cell damage and increased membrane permeability.