MYCOBIOTA AND CO-OCCRURENCE OF MYCOTOXINS IN GREEN AND ROASTED COFFEE BEANS

Abstract

A total of 20 samples of green and roasted coffee beans (the same varieties as green coffee beans were used) [Coffea arabica L. (19 samples) and Coffea robusta L. (1 sample)] were collected from the various coffee roasters in Slovakia (2017/2020) and their mycobiota were analyzed. Mycological analysis was carried using standard media with focus on genera Aspergillus and Penicillium. To determine endogenous and exogenous mycobiota the method of direct placing of surface-sterilized coffee beans (green and roasted) on agar plates and the plate dilution method were used. All obtained pure cultures were classified into the genera and identified to the species according to micro- and macromorphological properties. Next the potentially toxigenic isolates were tested on their ability to produce mycotoxins (cyclopiazonic acid, penitrem A, sterigmatocystin, aflatoxins (AFB₁, AFG₁), ochratoxin A, patulin, roquefortine C, citrinin, and griseofulvin). From green coffee samples with higher isolation frequency (FR%) and relative density (RD%) were the genus Aspergillus (FR 100% and RD 67.39%) and the genus Penicillium (FR 90% and RD 24.60%) recorded. Aspergillus section Nigri was the most widespread in green coffee samples (RD 47.7%). The genus Aspergillus was the most occurred genus in roasted coffee bean samples, too (RD 36.58%; FR 90%). In green and roasted coffee samples were detected mainly producers of aflatoxins (AFB₁ and AFG₁), cyclopiazonic acid, OA, sterigmatocystin and patulin. Due to the detected presence of mycotoxins in green as well as in roasted coffee bean samples, it is very important to prevent fungal contamination and control of coffee beans before and after roasting process.