Evaluation of Growth of Toxigenic Strain of Aspergillus flavus on Turmeric-Based Media at Different Water Activities

Abstract

Climatic conditions of the rain forest ecological zone of Nigeria favour the growth of Aspergillus flavus and subsequent aflatoxin production. This study was carried out to investigate the effect of water activity (0.85, 0.9, 0.95, 0.98 and 0.995 a ) on the lag phase prior to growth and mycelial growth of a toxigenic strain of A. flavus on turmeric-based media at 28±2oC after 12 days incubation period. Four different varieties; UT14, UT25, UT35 and UT46 obtained from National Root Crop Research Institute (NRCRI), Abia State and used in the preparation of the different media. A toxigenic strain of A. flavus isolated from turmeric in Port Harcourt was used in the experiment. The experiment was a 5 x 4 factorial laid out in completely randomized design (CRD), replicated three times. Results showed that regardless of the variety, no growth was observed at 0.85 a at 12 days of incubation. The shortest lag phase prior to growth was obtained at 0.995 a and the longest obtained at 0.90 a Optimal growth was observed at 0.98 a in three varieties (UT14, UT25and UT46), UT35 had marginal optimal growth at 0.995 a . Minimal growth of the A. flavus strain was obtained at 0.90 a at 28±2oC in all varieties. This result could be useful in the storage of turmeric, as this food product could be stored at moisture content of < 85%.