The combined effects of water activity (aw), storage temperature, headspace oxygen and
carbon dioxide concentrations on the growth of, and aflatoxin production by Aspergillus
flazus on sterile peanuts were examined using a process optimization technique termed
response surface methodology (RSM). Regression analysis of the data indicated that aw,
storage temperature and initial headspace oxygen concentration were all significant factors
(P < 0.001) affecting the growth of, and aflatoxin production by A. flaL, us. Extensive growth
and aflatoxin production occurred during the first week of storage in most treatment
combinations. Maximum growth occurred in peanuts with an a w of 0.97, a storage temperature
of 25°C and headspace oxygen of 10% (balance 60 : 40 carbon dioxide : nitrogen), after
21 days of storage while maximum aflatoxin production occurred at a lower a w of 0.94, after
21 days under similar storage/gaseous conditions. In several treatment combinations, where
high levels of aflatoxin (> 20 ng/g) were initially detected, aflatoxin concentration decreased
during storage to levels less than the current regulatory limit of 20 ng/g. This study
has shown that A. flaeus can grow and produce aflatoxin in carbon dioxide enriched
atmospheres in the presence of oxygen. It also emphasizes the combined effect of several
'barriers' to inhibit and reduce aflatoxin in MAP products containing various levels of
residual oxygen.
Key words: Aspergillus flavus; Response
The combined effects of water activity (aw), storage temperature, headspace oxygen and
carbon dioxide concentrations on the growth of, and aflatoxin production by Aspergillus
flazus on sterile peanuts were examined using a process optimization technique termed
response surface methodology (RSM). Regression analysis of the data indicated that aw,
storage temperature and initial headspace oxygen concentration were all significant factors
(P < 0.001) affecting the growth of, and aflatoxin production by A. flaL, us. Extensive growth
and aflatoxin production occurred during the first week of storage in most treatment
combinations. Maximum growth occurred in peanuts with an a w of 0.97, a storage temperature
of 25°C and headspace oxygen of 10% (balance 60 : 40 carbon dioxide : nitrogen), after
21 days of storage while maximum aflatoxin production occurred at a lower a w of 0.94, after
21 days under similar storage/gaseous conditions. In several treatment combinations, where
high levels of aflatoxin (> 20 ng/g) were initially detected, aflatoxin concentration decreased
during storage to levels less than the current regulatory limit of 20 ng/g. This study
has shown that A. flaeus can grow and produce aflatoxin in carbon dioxide enriched
atmospheres in the presence of oxygen. It also emphasizes the combined effect of several
'barriers' to inhibit and reduce aflatoxin in MAP products containing various levels of
residual oxygen.
Key words: Aspergillus flavus; Response
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