Storage Fungi and Mycotoxins Associated with Rice Samples Commercialized in Thailand

Abstract

The study focused on the examination of the different fungal species isolated from commercial rice samples applying conventional culture techniques as well as different molecular and phylogenic analyses to confirm phenotypic identification. Additionally the mycotoxin production and contamination were analyzed using validated liquid chromatography杢andem mass spectrometry (LC-MS/MS). In total 40 rice samples were obtained covering rice berry red jasmine rice brown rice germinated brown rice and white rice. The blotting paper technique applied on the 5 different types of rice samples detected 4285 seed-borne fungal infections (26.8%) for 16 000 rice grains. Gross morphological data revealed that 19 fungal isolates belonged to the genera Penicillium/Talaromyces (18 of 90 isolates; 20%) and Aspergillus (72 of 90 isolates; 80%). To check their morphologies molecular data (fungal sequence-based BLAST results and a phylogenetic tree of the combined ITS BenA CaM and RPB2 datasets) confirmed the initial classification. The phylogenic analysis revealed that eight isolates belonged to P. citrinum and additionally one isolate each belonged to P. chermesinum A. niger A. fumigatus and A. tubingensis. Furthermore four isolates of T. pinophilus and one isolate of each taxon were identified as Talaromyces (T. radicus T. purpureogenum and T. islandicus). The results showed that A. niger and T. pinophilus were two commonly occurring fungal species in rice samples. After subculturing ochratoxin A (OTA) generated by T. pinophilus code W3-04 was discovered using LC-MS/MS. In addition the Fusarium toxin beauvericin was detected in one of the samples. Aflatoxin B1 or other mycotoxins such as citrinin trichothecenes and fumonisins were detected. These preliminary findings should provide valuable guidance for hazard analysis critical control point concepts used by commercial food suppliers including the analysis of multiple mycotoxins. Based on the current findings mycotoxin analyses should focus on A. niger toxins including OTA and metabolites of T. pinophilus (recently considered a producer of emerging mycotoxins) to exclude health hazards related to the traditionally high consumption of rice by Thai people. ? 2023 by the authors.