Emerging risks, modified mycotoxins.

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Modified mycotoxins are toxic secondary metabolites produced by fungi either generated as part of the defense mechanism of the infected plant or formed during food processes. (1)

The possibility of conversion of the modified mycotoxin to its free form may pose a risk to humans and animals. Modified forms are almost never detected during analysis for progenitor mycotoxins, and no maximum limits are in effect.

It is critical for food safety to delve into the analytical, toxicological, and risk exposureassessment aspects of these metabolites.

Modified mycotoxins. What are they?

Modified mycotoxins are toxic secondary metabolites of mycotoxins (2); they can be produced by plants to defend themselves against the parasitic fungus that produces the mycotoxins or the fungus that spreads them in the host but can also be derived from other sources.

The number and type of modified mycotoxins found in food and feed is a function of several environmental, biological, chemical and physicochemical variables.

How they are originated

Some studies, in fact, have shown the possibility that modified mycotoxins are produced during metabolic processes in animals and humans and during food processing. Therefore, it is necessary to make a distinction between the origin and the changes undergone by the modified mycotoxins. (3)

The primary and most widespread source is related to plant and fungal metabolism, while the secondary source is associated with biotransformations contributed by fungi, animals (including humans), mammalian metabolism, and food processing.

In addition to the plant infected with mycotoxin-producing fungi, some strains of yeast (Saccharomyces cerevisiae, Clonostachys rosea, Saccharomyces pastorianus), bacteria (Marmoricola sp., Acinetobacter, Leadbetterella and Gemmata), and filamentous fungi (Fusarium spp., Aspegillus spp., Rhizopus spp., Trichoderma spp., Thamnidium spp.) can modify mycotoxins, through their defense mechanisms and enzymatic activity.

Modified mycotoxins in food

Modified mycotoxins have been found in foods and feeds, especially grain-based ones.

The most frequently identified modified mycotoxin belongs to the fusariotoxin family, these are mainly mycotoxins modified from Zearalenone (ZEA), found in corn, wheat, wheat bran and vegetable oils. Additional studies have found mycotoxins modified by Deoxynivalenol (DON) in wheat, corn, oats, barley, beer, rye, breakfast cereals, and snacks.

Nivalenol-modified mycotoxins (NIVs) have been found in wheat and corn, with modified fumosins also found in the latter. Another family of mycotoxins produced byAspergillus and Penicillium is Ochratoxin A (4), studies have shown its presence in tomato, potato, corn, carrot, wheat, soybean and paprika.

Influence of environmental conditions

Research shows that climate change is a major factor in the spread of mycotoxins worldwide. Environmental conditions influence the development of both mycotoxins and their corresponding modified forms.

Mycotoxicoses, in fact, were considered more common in areas of developing countries. However, climate change is increasingly bringing mycotoxin contamination to industrialized countries, including the EU. Climate change, in fact, influences the ability of fungi to contaminate food and can lead to varying susceptibility of crops to fungal contamination.

Food processes

Some studies have shown the possibility that modified mycotoxins are produced during food processing (5).

The formation of modified mycotoxins may depend on the initial level of contamination, temperature increase, duration of the process, fermentation steps, use of additives and enzymes, physical and chemical processes (from the use of acids or bases), and the composition of the raw material.

A safe raw material can become a final product with high levels of mycotoxins (free and modified) due to the possibility of release of these compounds during processing. Therefore, the control of raw materials alone is not sufficient to ensure the toxicological safety of the final product.

Numerous studies, on the other hand, have shown that mycotoxins can be partially removed or modified through physical processes such as:

  • Heat treatment, peeling and grinding;
  • Chemical processes such as alkaline and acid treatment;
  • Biological processes such as fermentation.

However, removal methods have not yet been confirmed.

Toxicity and risk assessment

The toxicity of modified mycotoxins to humans and animals is still unknown, however, there is a potential risk of release of parent mycotoxins by hydrolysis during food processing and digestion in human and animal organisms (6). Because of this risk, EFSA decided that, during the risk assessment, the modified mycotoxin should be considered with the same toxicity as the parent mycotoxin (7).

Due to the lack of data on the exposure and toxic properties of these compounds, it is impossible to make a proper risk assessment for modified mycotoxins in food. Routine monitoring of food and feed is also impossible; in fact, although there are numerous LC/MS/MS analytical methods for the determination of modified mycotoxins in grains, validated analytical standards for modified mycotoxins are still lacking.

Available data, however, indicate that mycotoxins modified by DON, ZEA, and fumonisin B are obvious priorities because of their toxicity and potential exposure to humans and animals.

Conclusion

Few data are currently available on the stability, properties and conversion from one form to another during processing of modified mycotoxins. In addition to the toxicological harms established for known mycotoxins, modified mycotoxins represent a new level of complexity in toxicity assessment and the development of evidence-based risk analysis.

Recognizing toxicological relevance of modified mycotoxins in food products, and to make up for the lack of studies on the toxicity and processing mechanisms of mycotoxins that hinder the determination of the maximum tolerable level of these metabolites in foods, is a major challenge for the future that should be considered by the respective regulators, food manufacturers, and control authorities to protect the health of consumers.

Notes

(1) Freire L, Sant’Ana AS. Modified mycotoxins: An updated review on their formation, detection, occurrence, and toxic effects. Food Chem Toxicol. 2018 Jan;111:189-205. doi: 10.1016/j.fct.2017.11.021. Epub 2017 Nov 20. PMID: 29158197.

(2) Marta Strinati, Mycotoxins, the invisible evil. THE ABC’S. GIFT (Great Italian Food Trade).
24.5.19

(3) Angioni, A.; Russo, M.; La Rocca, C.; Pinto, O.; Mantovani, A. Modified Mycotoxins, a Still Unresolved Issue. Chemistry 2022, 4, 1498-1514. https://doi.org/10.3390/chemistry4040099

(4) Dario Dongo, Ylenia Patti Giammello. Food contaminants. New limits in EU on ochratoxin A from 1.1.23. GIFT (Great Italian Food Trade). 04.11.2022

(5) Berthiller, F., Crews, C., Dall’Asta, C., De Saeger, S., Haesaert, G., Karlovsky, P., Oswald, I.P., Seefelder, W., Speijers, G., Stroka, J., 2013. Masked mycotoxins: a review. Mol. Nutr. Food Res. 57, 165-186.

(6) Berthiller, F.; Schuhmacher, R.; Adam, G.; Krska, R. Formation, determination and significance of masked and other conjugated mycotoxins. Anal. Bioanal. Chem. 2009, 395, 1243-1252.

(7) European Food Safety Authority (EFSA), 2014. Scientific opinion on the risks for human and animal health related to the presence of modified forms of certain mycotoxins in food and feed. EFSA J. 12, 3916.

Giulia Pietrollini
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Graduated in industrial biotechnology and passionate about sustainable development.