Rapid elimination of foodborne and environmental fungal contaminants by benzo analogs

Authors: Kim, Jong Heon; Chan, Kathleen - Kathy; Mahoney, Noreen; Cheng, Luisa; TAUTGES, NICOLE - University Of California, Davis; SCOW, KATE - University Of California, Davis

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2020
Publication Date: 2/9/2020
Citation: Kim, J., Chan, K.L., Mahoney, N.E., Cheng, L.W., Tautges, N., Scow, K. 2020. Rapid elimination of foodborne and environmental fungal contaminants by benzo analogs. Journal of the Science of Food and Agriculture. 100(6):2800–2806. https://doi.org/10.1002/jsfa.10288.
DOI: https://doi.org/10.1002/jsfa.10288

Interpretive Summary: Contamination of foods by fungi is a recurring food safety and security issue, with outbreaks of commodity-specific food sources, such as corn or tree nut contamination by aspergilli producing hepato-carcinogenic mycotoxins, directly affecting the health and safety of the public. It has been estimated that fungi cause 60 to 70 % of world food/crop loss. Natural products or their structural derivatives have been investigated as new, safe antifungal agents, which not only inhibit the growth of fungi, but also disrupt their production of mycotoxins. We used commercial organic apple and grape juices as the experimental food matrices, and also used soils of crop fields as the source of environmental fungal contaminants. We found that trans-cinnamaldehyde showed the highest antifungal activity against ten filamentous fungi, including mycotoxin-producing (A. flavus, A. parasiticus, Penicillium expansum), pathogenic (Aspergillus fumigatus) and heat-resistant food-spoilage (Neosartorya fischeri) fungi. In summary, trans-cinnamaldehyde could be developed as a potent antifungal agent against various fungal sources with the potential of cost reductions, viz., lowering food processing time, energy use, etc.

Technical Abstract: Contamination of foods or environments by fungi, especially those resistant to conventional fungicides or drugs, is problematic. The objective of this study is to identify safe, natural antifungal agents that can rapidly (24 h cutoff) remove fungal pathogens or contaminants from food and/or environmental sources. Fifteen antifungal compounds (nine benzo derivatives as candidates; six conventional fungicides as references) were investigated. Three benzo analogs, namely, octyl gallate (OG), trans-cinnamaldehyde (CA) and 2-hydroxy-5-methoxybenzaldehyde (2H5M), at 0.1% (w/v) achieved more than 99.9% fungal death after 0.5, 2.5 or 24 h of treatments, respectively, in in vitro phosphate buffered saline (PBS) bioassay. However, when OG, CA and 2H5M were examined in commercial food matrices, organic apple or grape juices, only CA maintained similar level of antifungal activity, compared to PBS bioassay. CA showed higher antifungal activity at pH 3.5, equivalent to that of commercial fruit juices, than at pH 5.6. In soil sample tests, application of 0.1% (w/v) CA to conventional corn/tomato field samples (pH 6.8) for 2.5 h resulted in more than 99.9% fungal death, indicating CA could also eliminate fungal contaminants in soil. While the conventional fungicide thiabendazole exerted antifungal activity comparable to CA, thiabendazole enhanced the production of carcinogenic aflatoxins by Aspergillus flavus, an undesirable side-effect. In conclusion, CA could be developed as a potent antifungal agent in food processing or soil sanitation by reducing time/costs necessary for fungal removal.