GROWTH OF AND AFLATOXIN PRODUCTION BY ASPERGILLUS-FLAVUS IN PEANUTS STORED UNDER MODIFIED ATMOSPHERE PACKAGING (MAP) CONDITIONS

The combined effects of water activity (a(w)), storage temperature, he adspace oxygen and carbon dioxide concentrations on the growth of, and aflatoxin production by Aspergillus flavus on sterile peanuts were ex amined using a process optimization technique termed response surface methodology (RSM). Regression analysis of the data indicated that a(w) , storage temperature and initial headspace oxygen concentration were all significant factors (P < 0.001) affecting the growth of, and aflat oxin production by A. flavus. Extensive growth and aflatoxin productio n occurred during the first week of storage in most treatment combinat ions. Maximum growth occurred in peanuts with an a(w) of 0.97, a stora ge temperature of 25-degrees-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 combina tions, where high levels of aflatoxin (> 20 ng/g) were initially detec ted, aflatoxin concentration decreased during storage to levels less t han the current regulatory limit of 20 ng/g. This study has shown that A. flavus can grow and produce aflatoxin in carbon dioxide enriched a tmospheres in the presence of oxygen. It also emphasizes the combined effect of several 'barriers' to inhibit and reduce aflatoxin in MAP pr oducts containing various levels of residual oxygen.