Antifungal effects of three natural branched medium-chain fatty acids and their potential as fumigants against Aspergillus flavus in stored peanut seeds

Authors: YANG, YUQI - Henan University Of Technology; MA, WEIBIN - Henan University Of Technology; Johnson, Eric; XIE, YANLI - Henan University Of Technology; ZHAO, RENYONG - Henan University Of Technology

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2024
Publication Date: 10/17/2024
Citation: Yang, Y., Ma, W., Johnson, E.T., Xie, Y., Zhao, R. 2024. Antifungal effects of three natural branched medium-chain fatty acids and their potential as fumigants against Aspergillus flavus in stored peanut seeds. Food Control. https://doi.org/10.1016/j.foodcont.2024.110950.
DOI: https://doi.org/10.1016/j.foodcont.2024.110950

Interpretive Summary: Peanuts can be contaminated at harvest with fungi that produce toxic compounds called mycotoxins. A mycotoxin is a toxic compound synthesized by fungi that can cause disease or death in humans and animals. One type of mycotoxin called aflatoxin has the potential to cause cancer in humans. The cost of aflatoxin mitigation to the peanut industry in the United States averaged $84 million between 2017 and 2019. Three naturally occurring fatty acids, which are the primary components of lipids or fats, derived from plants and animals were utilized to completely inhibit growth of aflatoxin-producing fungi that were applied to peanuts. The three fatty acids are volatiles that are utilized in the food industry as flavoring substances, and generally recognized as safe, but they have not previously been utilized for control of fungal growth in peanuts during post-harvest storage. The fatty acids were most effective at inhibiting fungi when used as fumigants compared to liquid contact. After 24 hours of fumigation exposure to the fatty acids, the peanut seeds infected with an aflatoxin producing fungus was completely killed. This research demonstrates that these safe, volatile chemicals can be used as fungal growth control molecules during peanut storage.

Technical Abstract: The contamination of peanuts with aflatoxins predominantly produced by Aspergillus flavus poses a worldwide threat to both food safety and agricultural economies. Antifungal compounds from natural sources may offer a safe and effective alternative strategy to control A. flavus in peanuts. We evaluated the contact and fumigant antifungal effects of three natural branched medium-chain fatty acids (branched-MCFAs), (E)-2-methyl-2-pentenoic acid, 2-methylhexanoic acid, and 2-methylheptanoic acid against A. flavus relative to their straight-chain isomers and sorbic acid a commonly used preservative. In vitro experiments showed that the inhibitory effects of these three branched-MCFAs on A. flavus were stronger than their straight-chain isomers and sorbic acid. In addition, fumigant effects of the branched-MCFAs were more effective than their direct contact inhibitory effects against the growth of A. flavus. 2-Methylhexanoic acid, 2-methylheptanoic acid, and (E)-2-methyl-2-pentenoic acid showed significant fumigant activity, with the minimum inhibitory concentration (MIC) values of 0.10, 0.10, and 0.12 g/l air, respectively. Fumigation of these branched-MCFAs also significantly slowed the growth of A. flavus in peanut seeds, and completely inhibited A. flavus growth at 2.0 g/l air. After 24 h of fumigation exposure to the branched-MCFAs, the fumigated A. flavus on medium or peanut seeds was re-incubated to observe whether the A. flavus could continue to grow, and the results revealed that the in vitro and in vivo minimum fungicidal concentrations (MFC) were 0.15 and 2.5 g/l air, respectively. This study indicated that these three natural branched-MCFAs have strong antifungal fumigation activity with application potential in protecting peanut seeds from A. flavus contamination during storage.