Resilience of Aspergillus westerdijkiae Strains to Interacting Climate-Related Abiotic Factors: Effects on Growth and Ochratoxin A Production on Coffee-Based Medium and in Stored Coffee
2020
Akbar, Asya | Medina, Ángel | Magan, N. (Naresh)
We examined the resilience of strains of Aspergillus westerdijkiae in terms of growth and ochratoxin A (OTA) production in relation to: (a) two-way interacting climate-related abiotic factors of water activity (aw, 0.99–0.90) × temperature (25–37 °C) on green coffee and roasted coffee-based media; (b) three-way climate-related abiotic factors (temperature, 30 vs. 35 °C; water stress, 0.98–0.90 aw; CO₂, 400 vs. 1000 ppm) on growth and OTA production on a 6% green coffee extract-based matrix; and (c) the effect of three-way climate-related abiotic factors on OTA production in stored green coffee beans. Four strains of A. westerdijkiae grew equally well on green or roasted coffee-based media with optimum 0.98 aw and 25–30 °C. Growth was significantly slower on roasted than green coffee-based media at 35 °C, regardless of aw level. Interestingly, on green coffee-based media OTA production was optimum at 0.98–0.95 aw and 30 °C. However, on roasted coffee-based media very little OTA was produced. Three-way climate-related abiotic factors were examined on two of these strains. These interacting factors significantly reduced growth of the A. westerdijkiae strains, especially at 35 °C × 1000 ppm CO₂ and all aw levels when compared to 30 °C. At 35 °C × 1000 ppm CO₂ there was some stimulation of OTA production by the two A. westerdijkiae strains, especially under water stress. In stored green coffee beans optimum OTA was produced at 0.95–0.97 aw/30 °C. In elevated CO₂ and 35 °C, OTA production was stimulated at 0.95–0.90 aw.
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