Abstract
In this paper, a study of fungal and multi-mycotoxin contamination in 140 Camellia sinensis and 26 herbal teas marketed in Latvia is discussed. The analysis was performed using two-dimensional liquid chromatography with time-of-flight mass spectrometry (2D-LC-TOF-MS) and MALDI-TOF-MS. In total, 87% of the tea samples tested positive for 32 fungal species belonging to 17 genera, with the total enumeration of moulds ranging between 1.00 × 101 and 9.00 × 104 CFU g−1. Moreover, 42% of the teas (n = 70) were contaminated by 1 to 16 mycotoxins, and 37% of these samples were positive for aflatoxins at concentrations ranging between 0.22 and 41.7 µg kg−1. Deoxynivalenol (DON) and its derivatives co-occurred in 63% of the tea samples, with their summary concentrations reaching 81.1 to 17,360 µg kg−1. Ochratoxin A (OTA), enniatins, and two Alternaria toxins were found in 10–37% of the teas at low concentrations. The dietary exposure assessment based on the assumption of a probable full transfer of determined mycotoxins into infusions indicated that the analysed teas are safe for consumers: the probable maximum daily exposure levels to OTA and the combined DON mycotoxins were only 0.88 to 2.05% and 2.50 to 78.9% of the tolerable daily intake levels.
Highlights
Traditional Camellia sinensis (C. sinensis) black and green teas, and teas made from medicinal herbs such as peppermint, chamomile, and dog-rose, are consumed daily as the most favoured beverages in Europe and other countries [1,2]
The authors of this study reported that 10 out of 18 herbal teas had fungal mould contents ranging between 5.00 × 103 and 1.00 × 106 colony-forming unit (CFU) g−1, which notably exceeded the standard limitations for total fungi, whereas the mould levels dropped to the relevant limitations after tea brewing, unlike the bacterial counts, which were not reduced in herbal teas after preparing the tea infusions [47]
This study demonstrated advances in the 2D-LC-TOF-MS method for the simultaneous quantification of regulated and emerging mycotoxins produced by Alternaria, Aspergillus, Penicillium, and Fusarium strains and their secondary derivatives in 166 commercial teas, including traditional and novel Pu-erh and oolong teas, as well as common herbal teas available at retail stores and from tea houses
Summary
Traditional Camellia sinensis (C. sinensis) black and green teas, and teas made from medicinal herbs such as peppermint, chamomile, and dog-rose, are consumed daily as the most favoured beverages in Europe and other countries [1,2]. C. sinensis and C. assamica varieties, such as oolong (semi-fermented) and Pu-erh (post-fermented) teas, have spread around the world and gained popularity among non-Asian tea users due to their multiple health-protective (antioxidant, antiobesity, antibacterial, and antitumor) properties associated with the high contents of catechins, flavanols, and specific fungal microbiota present in these teas [3,4]. The production of the ripened (shu) Pu-erh tea variety from loosened black tea leaves involves wet-piling fermentation, which can enhance the development of moulds and the potential formation of mycotoxins compared to the aging conditions of raw (sheng) Pu-erh tea, which is produced from nonfermented tea leaves [6,7]
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