Estimation of fungal contamination of various plant materials with UV-determination of fungal ergosterol

摘要

This study presents an estimation of mould contamination of 31 samples of various herbs and spices, cereals, fruits and vegetables, as well as a comparison of two methods of mould estimation: dilution plate method and UV-determination of ergosterol. The correlation coefficients between ergosterol content and colony forming unit ranged from R=0.663 for cereals to R=0.694 for herbs and spices; there was no significant correlation for fruits and vegetables. Results of ergosterol content in various morphological forms of moulds—spores, and living and non-living mycelium—are also presented. It was found that pasteurisation did not alter ergosterol content in mycelium. Ergosterol synthesis in cultures on wheat, marjoram and tomato paste was investigated. Ergosterol production on tomato paste medium was inhibited due to the low pH of the medium—a medium pH lower than 4.5 inhibits ergosterol synthesis. The novelty of this work is the indication that there is no relationship between fungal biomass and ergosterol content in acidic products (juices, fruits, tomato paste). Thus, the application of ergosterol as an indicator of mould contamination in these products must be verified using the dilution plate method.