Effect of water activity and temperature on mycelial growth and ochratoxin A production by isolates of Aspergillus ochraceus on irradiated green coffee beans.
Aspergillus ochraceus as a fungal contaminant and ochratoxin A (OTA) producer plays an important role in coffee quality. Temperature and water activity (a(w)) significantly influence mycelial growth and OTA production by isolates of A. ochraceus on green coffee beans. Maximum mycelial growth was found at 30 degrees C and 0.95 to 0.99 a(w). A marked decrease in growth rate was observed when temperature and a(w) were reduced. At 0.80 a(w), mycelial growth occurred only at 30 and 20 degrees C for one isolate. Maximum OTA production was found at 20 degrees C and 0.99 a(w). At 10 degrees C, OTA was not produced, regardless of a(w). Similarly, no OTA was detected at 0.80 a(w). OTA production ranged from the limit of detection (40 ng g(-1) of green coffee) to 17,000 ng g(-1) of green coffee. Significant intraspecific differences in mycelial growth and OTA production were found. Primary data for lag phases prior to mycelial growth under the influence of temperature and a(w) were modelled by multiple linear regression, and the response surface plots were obtained.
Pardo
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Department of Food Technology, Lleida University, CeRTA-UTPV, Rovira Roure 191, 25198 Lleida, Spain.
Marín
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S
Ramos
A J
AJ
Sanchis
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V
D001235:Aspergillus ochraceus / Q000254:growth & development* / Q000378:metabolism; D003069:Coffee / Q000382:microbiology*; D005506:Food Contamination; D005514:Food Irradiation / Q000379:methods*; D005516:Food Microbiology; D005720:Gamma Rays; D016014:Linear Models; D008954:Models, Biological; D009793:Ochratoxins / Q000096:biosynthesis*; D011237:Predictive Value of Tests; D013696:Temperature; D014867:Water / Q000378:metabolism
D003069:Coffee; D009793:Ochratoxins; D014867:Water; C025589:ochratoxin A