Methods for sustainable control
The best way to prevent the presence of mycotoxins in food is to avoid the development of producing fungi. So far, the most effective methods to achieve this are chemical fungicides applied both in the field and during food storage. However, residues of these compounds can pose serious risks to human health and the environment, which is why the European Union regulates the maximum limits of these residues in foodstuffs. Therefore, it is essential to search for new, more sustainable and safer control methods to prevent fungal growth and thus ensure that foodstuffs are free of mycotoxins. In this respect, the use of safe microorganisms as biological control agents is one of the most promising strategies.
Our group is focused on the development of biological control methods to prevent the growth of the main toxigenic fungi in the field using two approaches: (1) eliminating the initial inoculum of the fungus in the soil, and (2) preventing the colonisation of the fungi on the fruit. It has long been known that the soil is the reservoir for toxigenic fungi from one season to the next. There they remain dormant until they can re-infect the plant the following harvest season. Therefore, by attacking the fungus in the soil, future colonisation and damage can be prevented. In recently published studies, we have isolated and characterised microorganisms from vineyard soil and found them to be effective in controlling the main toxigenic fungi. The greatest potential in the control of these fungi has been observed in actinobacteria of the genera Arthrobacter and Pseudoarthrobacter, whose presence not only prevents the growth of the fungus but also drastically reduces its capacity to produce mycotoxins (De la Huerta et al., 2022). On the other hand, the second strategy is aimed at preventing colonisation of the plant by toxigenic fungi. In this sense, it is necessary to select indigenous microorganisms that are very well adapted to survive and colonise this product. So far, we have characterised the yeast Hanseniaspora uvarum U1 as a potential biological control agent against toxigenic fungi in grapes (Gómez-Albarrán et al., 2021).
Another alternative control strategy with better results is the application of natural compounds with antifungal properties. In our research group, we have evaluated the potential of essential oils from aromatic plants to control the growth and production of aflatoxins by Aspergillus flavus in maize (GarcÃa-DÃaz et al., 2020). The in vitro effectiveness of these essential oils is very high, but their easy volatilisation and intense odour require the development of advanced technologies for their application in food. Therefore, we have developed a method of encapsulation of oregano essential oil using niosomes that allow a prolonged release of the compounds. In this way, we have been able to delay the growth and aflatoxin production of A. flavus for more than 60 days in stored maize grains (GarcÃa-DÃaz et al., 2019).
