Fungi and mycotoxins in capsicum powderoccurrence, ecophisiology and control

Resumen

Mycotoxins are secondary metabolites of fungal origin, which commonly contaminate various foods and agricultural products. The study of mycotoxins in foodstuffs is complex because adequate sampling techniques are not commonly used and not all mycotoxin-producing fungi and their mycotoxins are known. Co-occurrence of mycotoxins is a key factor to understand mycotoxin interactions and synergetic effects. To date, only few studies on the co-occurrence of mycotoxins in food commodities have been carried out. The main objective of this Thesis was to extend the knowledge on mycotoxin contamination of Capsicum powder, focusing in the analysis of the co-occurrence of the main mycotoxin-producing fungi and the most important mycotoxins. For the accomplishment of this objective traditional mycology methods allied with molecular biology techniques for moulds identification were used, along with chromatographic methods for mycotoxin determination and predictive mycology for studying the mycotoxins control strategies. A representative amount of Capsicum powder samples, collected according to the EU legislation in bulk or in detail, were analysed for fungal load and mycotoxin contamination. Yeasts were present in all contaminated Capsicum powder samples, while filamentous fungi were not always found. The most common genera found were Aspergillus and Eurotium. The presence of potentially mycotoxigenic moulds was observed, mainly from Aspergillus sections Flavi, Circumdati and Nigri, and also different isolates from the genus Fusarium. With regard to mycotoxins, aflatoxins (AF), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), T-2 and HT-2 toxins were analyzed. The co-occurrence of more than one mycotoxin in the same sample was observed, OTA being the most frequent. When analysing the mycotoxin control strategies, it was observed that both growth and mycotoxins production can be controlled for Aspergillus flavus, A. ochraceus, A. tubingensis and A. westerdijkiae if low temperatures of storage were fulfilled (T < 15º C). However, the simultaneous use of physical and chemical control can improve the control of mycotoxin production. The use of a natural Capsicum carotenoids mixture (named capsantal) had an inconclusive effect over AF and OTA production, although at 25 ºC capsantal could reduce the growth rates of A. flavus, A. ochraceus, A. tubingensis and A. westerdijkiae. The use of fungicides could be a prime strategy in mycotoxin control. It was observed that some fungicides, like mancozeb, can simultaneously control fungal growth and mycotoxins production in A. flavus, A. ochraceus, A. tubingensis and A. westerdijkiae.