engleski

Occurrence of aflatoxin B1, sterigmatocystin and ochratoxin A in olive oil and their production on black olives

Olives can be contaminated with various moulds particularly Aspergillus species. Several reports showed that olives support growth of mycotoxin-producing aspergilli as well as production of aflatoxin (AFB1) and ochratoxin A (OTA) during storage period. Therefore, these and other lipid soluble mycotoxins could be transferred into olive oil. The aim of this study was to determine the presence of AFB1, OTA and sterigmatocystin (STC) in olive oil samples (N=48) collected in 2009 from several producers in Dalmatia (Croatia). Production ability of Aspergillus mycotoxin-producing strains on pickled black olives as substrate was also checked. Upon methanol (80%) extraction, HPLC (UV Vis or FLD detection) was employed for analysis of oil samples as well as black olives that were used as substrate for mycotoxin biosynthesis. 52% of oil samples were contaminated with STC (0.003-0.028 g/mL) while two samples (4%) contained STC in concentrations below limit of quantification (LOQ). AFB1 recovered from 12.5% of samples (0.772-3.104 g/mL), while OTA was detected only in one oil sample and it was below LOQ. STC and AFB1 co-occurred in 6.25% of samples. Mycotoxin-producing Aspergillus strains were able to produce AFB1 (17.35 g/g) and STC (0.237 g/g) but not OTA on black olives. These results indicate that STC, which is precursor of aflatoxin biosynthesis in A. flavus and A. parasiticus and also the end mycotoxin in secondary metabolism of other aspergilli, could be more frequently expected in olive oil than AFB1 and OTA. To our knowledge this is the first report on mycotoxin contamination of olive oil in Croatia.

Aspergillus; olive; aflatoxin; ochratoxin; sterigmatocystin

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