The University of Zimbabwe (2002) studied the presence of aflatoxin in peanut butter. Among four different methods of processing (traditional, hand, motorized, commercial) traditional methods consistently had the lowest concentrations and commercial processors consistently had the highest concentrations of aflatoxin.
Samples were taken in January, April and August. All peanut butter samples processed traditionally had aflatoxin concentrations below 20ppb (the level that formal markets have set for aflatoxin contamination). Commercial peanut butter had the highest number of contaminated samples (93.75%).
Generally, all processing methods showed some percentage of undesirable aflatoxin levels, indicating the need for education on aflatoxin awareness.
Aflatoxin levels were highest in the January samples, with a reduction during April and August (except for commercial processing), indicating a possible seasonal fluctuation of aflatoxin in storage.
The lower levels of aflatoxin in traditional and hand processing could be due to the use of quality nuts, and to more thorough selection (since low volumes of nuts are used).
Two possible reasons for high aflatoxin levels are the use of poor grade nuts and poor storage from the time of purchase to processing.
Aflatoxin occurred across all natural regions, suggesting that weather conditions are not a determining factor.
Reference: Improved Peanut Butter Processing. University of Zimbabwe, 2002. Part 4. Prevalence of Aflatoxins in Rural Small Scale and Commercial Production. pp 82-89
ECHO Staff 2005. Aflatoxin in Peanut Butter. ECHO Development Notes no. 88