Effect of inoculum level on aflatoxin production by Aspergillus flavus under modified atmosphere packaging (MAP) conditions

Abstract

The combined effect of inoculum level and other environmental factors (water activity, storage temperature and level of headspace oxygen) on the growth and aflatoxin production by Aspergillus flavus under MAP conditions on a synthetic medium was studied using a full factorial experimental design. Regression analysis of the data showed that inoculum level, water activity (aw), storage temperature and headspace O2 all had a significant effect on both growth of, and aflatoxin production by, A. flavus. Maximum growth (4·17 mg g-1) occurred at an inoculum level of 104 spores per plate, an aw of 0·95, storage temperature of 20°C and headspace O2 of 15% (balance CO2:N2 (60%:40%)). However, maximum aflatoxin level of 3·45 μg g-1 (3450 ng g-1) occurred at an inoculum level of 103 spores per plate, an aw of 0·96, storage temperature of 25°C and a reduced level of headspace O2 (10%). Packing under almost completely anaerobic conditions using Ageless oxygen absorbents inhibited both growth and aflatoxin production by A. flavus, irrespective of the inoculum levels and storage temperature used.