Even fungi have their own “cup of tea”

Abstract

Tea has a long tradition of use in folk medicine and is a widely popularized as a recreational beverage. In that sense, it is of high importance to examine fungal presence in different teas. A total of nine herbal tea samples: Mentha piperita (peppermint), Thymus vulgaris (thyme), Urtica dioica (common nettle), Hypericum perforatumI (St John's wort), Camellia sinensis (green tea), Crataegus monogyna (hawthorn), Arctostaphylos uva ursi (common bearberry), Sambucus nigra (black elder) and Achillea millefolium (yarrow) were tested for the presence of microfungi. Due to the low water activity (aw) of examined substrata two selective media for fungal isolation, which favor growth of xerophilic fungi, were used: MY40 and DG18. The highest fungal contamination of tested tea samples were documented on DG18 for M. piperita and S. nigra samples, 859.26 and 737 CFUg-1, respectively, while moderate fungal contamination (318.51 CFUg-1) was documented for green tea. The majority of documented fungi belong to genus Aspergillus, which were documented in all tested herbal tea samples. Cladosporium spp., Mucor sp., Penicillium spp., and Rhizopus stolonifer were less frequent. The highly xerophylic Aspergillus species, members of section Aspergilli, were documented in all tested samples, exept in common bearberry. During cultivation period an abundance of cleistothecia with ascospores, typical for teleomorphic state of the section Aspergilli, Eurotium spp. was recorded. Aspergillus species are well known mycotoxin producers and causative agents of allergies and mycoses. Hence, their presence in tea must not be neglected.