Carbon dioxide production as an indicator of Aspergillus flavus colonisation and aflatoxins/cyclopiazonic acid contamination in shelled peanuts stored under different interacting abiotic factors

This study evaluated the relationship between storage of shelled peanuts under interacting abiotic conditions on (a) the temporal colonisation kinetics and cumulative respiration rates, (b) quantified the effect on dry matter losses (DMLs) and (c) quantify accumulation of aflatoxin B1 (AFB1) and CPA. Both naturally contaminated and inoculated peanuts with A. flavus conidia were stored for 7-days under different water activity (aw; 0.77-0.95) and temperature levels (20-35°C). Gas Chromatography (GC-TCD) was used to measure the temporal respiration rates (R) and the total accumulated CO2 production. Mycotoxin contamination was quantified at the end of the storage period by LC-MS/MS. There was an increase in the temporal CO2 production rates in wetter and warmer conditions in all treatments, with the highest respiration in the 0.95 aw treatments of stored peanuts + A. flavus inoculum at 30°C (2474 mg CO2 kg-1 h-1). The DMLs were modelled to produce contour maps of the environmental conditions resulting in maximum/minimum losses. Maximum mycotoxin contamination was always at 0.95 aw although optimal temperatures were different for AFB1 and CPA. Thus, 30-35°C was optimum for CPA and 25-30°C for AFs. A significant positive correlation (Spearman p<0.0001) were found between Log10AFB1 and Log10DML in both naturally contaminated stored peanuts (r2=0.7744) and that inoculated with A. flavus (r2=0.8464). Small dry matter losses (0.56%) resulted in AFB1 contamination above the EU...
Source: Fungal Biology - Category: Biology Source Type: research