REPOSITORY > RESULTS

Abstract

Mycotoxins are very stable toxic secondary metabolites produced by food contaminating
filamentous fungal species. The variability of their chemical structure leads to a diversity of
toxicities, including carcinogenicity, mutagenicity, teratogenicity, neurotoxicity and the immune
and endocrine disruption. Today, 25% of the global cereal stock is contaminated with mycotoxins
and unsuitable for consumption, which results in enormous economic losses. The incidence of
mycotoxin food contamination is growing, and is problematic since it represents one of the main
dietary risks. The increasing trend of mycotoxigenic fungi is mostly attributed to massive‐scale
food production, incorrect practices and handling of the food during harvest time, transport and
storage, and climate change. Although the agriculture and food industry have explored a vast
number of possible preventative and decontamination approaches, the problem of mycotoxin
contamination remains unresolved. Thus, the development of a new and more effective method
is necessary.
In this thesis, non‐equilibrium cold atmospheric pressure plasma (CAP) is explored as a new
promising approach for the decontamination of mycotoxins and inactivation of moulds. To
achieve this, a highly efficient CAP system based on a surface barrier discharge (SBD) using
ambient air as a carrier gas was applied for the decontamination of aflatoxins (AF),
trichothecenes, fumonisins and zearalenone. CAP decontamination efficiency was compared to
commonly used ultraviolet C (UV‐C) irradiation and thermal treatment. Simultaneously, CAP
mould inactivation potential was investigated with a focus on mould species Aspergillus flavus.
Both direct exposure to the gaseous plasma and plasma‐activated liquid broth (PAB) were
compared to the conventional disinfectant Virkon®. The physical‐chemical properties of CAP
were evaluated, the degradation of aflatoxin B1 (AFB1) was studied in detail to determine the
possible degradation products and pathways, and toxicity testing was performed.
It was demonstrated that CAP treatment of mycotoxins led to either their complete removal
or reduction to a concentration below the maximum levels allowed in selected food products. The
decontamination performance was found to be an order of magnitude higher in comparison to
UV‐C irradiation and thermal treatment. Moreover, the direct treatment with CAP successfully
inactivated the spores of A. flavus. Under comparable experimental conditions, no inactivation
was observed after the exposure of A. flavus to a standard 1% solution of Virkon®. However, PAB
did not show the efficacy comparable to the direct treatment as a result of the intense
hydrophobic properties of the surface of fungal spores. Analysis was performed on the CAPgenerated
reactive oxygen and nitrogen species (RONS) and it was determined that they
contributed the most to its decontamination and inactivation effect, excluding thermal effect and
plasma‐induced release of UV photons. A detailed analysis of CAP RONS‐induced degradation of
AFB1 demonstrated that the process was initiated through scission of the vinyl bond between C8
and C9 and continued through multiple pathways, resulting in the loss of the AFB1 toxicity.
Lastly, the presented PhD thesis provides the proof‐of‐concept of CAP removal of mycotoxin
contamination, which has the enormous potential for integration into already existing food
production lines as a new highly‐efficient and safe method for decontamination.