Aspergillus parasiticus NRRL 2667 Growth and Aflatoxin Synthesis as Affected by Calcium Content and Initial Spore Load in Single Peanuts

Abstract

Mycelial growth of Aspergillus parasiticus NRRL 2667 and aflatoxin production on Florunner peanuts grown under different calcium supplementation levels (CSL) (550, 1,100, 2,200 and 4,400 kg gypsum/ha) with initial spore loads of 102, 104 and 106 spores/g were investigated. Growth at 25°C for 0, 4, 7 and 14 days was determined by viable plate counts on Aspergillus flavus/parasiticus agar (AFPA) medium. Irrespective of the initial spore load, maximum growth of 108 to 109 CFU/g was attained after 14 days except for the 4,400 kg/ha Ca-supplemented nuts on which the maximum populations were one log less. Aflatoxins B1 and G1 concentrations measured by thin layer chromatography (TLC) ranged from 0–3460 (μg/g and 0–3740 (μg/g, respectively. Toxin production was highest in single peanuts with CSL of 2,200 kg/ha. A reduction of 50% or higher was observed as CSL was increased to 4,400 kg/ha.