Influence of water activity on physical properties, fungal growth, and Ochratoxin A production in dry cherries and 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 (aw) significantly influence mycelial growth and OTA production by isolates of A. ochraceus on green coffee beans. Maximum mycelial growth was found at 30°C and 0.95 to 0.99 aw. A marked decrease in growth rate was observed when temperature and aw were reduced. At 0.80 aw, mycelial growth occurred only at 30 and 20°C for one isolate. Maximum OTA production was found at 20°C and 0.99 aw. At 10°C, OTA was not produced, regardless of aw. Similarly, no OTA was detected at 0.80 aw. 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 aw were modelled by multiple linear regression, and the response surface plots were obtained.

Download Full-text

Collaborative Study of a Method for the Determination of Ochratoxin A in Green Coffee

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/58.2.258 ◽

1975 ◽

Vol 58 (2) ◽

pp. 258-262 ◽

Cited By ~ 2

Author(s):

Colette P Levi

Keyword(s):

Thin Layer ◽

Ochratoxin A ◽

Collaborative Study ◽

Green Coffee ◽

Average Recovery ◽

Semiquantitative Determination ◽

Chromatographic Methods ◽

Green Coffee Beans ◽

Coffee Beans

Abstract A method for the semiquantitative determination of ochratoxin A in green coffee has been studied collaboratively by 11 laboratories. The average recovery for the 7 samples spiked at 3 levels of ochratoxin A was 69.1%, ranging from 60.5 to 85.6%. This is comparable to other visual thin layer chromatographic methods of mycotoxin detection. The method has been adopted as official first action for the determination of ochratoxin A in green coffee beans.

Download Full-text

Ochratoxins A and B, Xanthomegnin, Viomellein and Vioxanthin Production by Isolates of Aspergillus ochraceus from Green Coffee Beans

Journal of Food Protection ◽

10.4315/0362-028x-46.11.965 ◽

1983 ◽

Vol 46 (11) ◽

pp. 965-968 ◽

Cited By ~ 13

Author(s):

MICHAEL E. STACK ◽

PHILIP B. MISLIVEC ◽

TURGUT DENIZEL ◽

REGINA GIBSON ◽

ALBERT E. POHLAND

Keyword(s):

High Performance Liquid Chromatography ◽

Liquid Chromatography ◽

Ochratoxin A ◽

High Performance ◽

Toxin Production ◽

Aspergillus Ochraceus ◽

Average Level ◽

Green Coffee ◽

Green Coffee Beans ◽

Coffee Beans

Isolates from Aspergillus ochraceus obtained from green coffee beans were cultured on rice and water. After 20 d of growth the cultures were extracted with chloroform and the extracts were analyzed by high performance liquid chromatography for ochratoxin A (OA), ochratoxin B (OB), xanthomegnin (X), viomellein (V) and vioxanthin (VX). Forty-three percent of the isolates produced OA at an average level of 397 μg of toxin/g rice, 17% produced OB at an average level of 312 μg/g, and 84% produced X, V, and VX at an average level of 281, 417 and 386 μg/g, respectively. The highest levels of toxin production were OA, 2088 μg/g; OB, 3375 μg/g; X, 1562 μg/g; V, 2514 μg/g; and VX, 2054 μg/g. VX has not previously been reported as an A. ochraceus metabolite.

Download Full-text