Post-harvest handling practices, moisture content, and aflatoxin levels of cassava from selected hammer milling centers in Uganda

Abstract

Cassava (Manihot esculenta) is a staple crop of significant economic and nutritional importance in Uganda. However, it is highly perishable, and root tubers are prone to rapid post-harvest deterioration due to microbial contamination. Poor handling practices such as drying on bare ground and improper storage, often contribute to aflatoxigenic fungi proliferation. Aflatoxins, secondary metabolites of these fungi are linked to liver cancer, immune suppression, and stunted growth in humans and animals. Thus, regular ingestion of aflatoxin-laden foodstuffs including cassava poses a serious public health risk. Despite awareness, aflatoxin monitoring in food matrices remains limited, especially in developing countries. This study assessed post-harvest handling practices, moisture content, and aflatoxin contamination and concentration levels in 120 randomly collected cassava samples from eight regional districts of Uganda. Post-harvest handling data were obtained through structured interviews with cassava processors at randomly selected milling centers. Moisture content was analyzed using the Hot-Air Oven, while aflatoxin contamination was determined through Thin Layer Chromatography (TLC). The Competitive-ELISA technique quantified aflatoxin concentrations. Handling practices included sun-drying on bare ground (9%), floor storage (44%), and 74 % of the mill caretakers having reported processing of moldy cassava for human consumption. Milling center caretakers relied on ineffective traditional methods [biting, touching, and breaking tests] and none reported the use of a moisture meter to assess moisture content. Moisture content ranged from 7.14% to 27.63%. Aflatoxins were detected in 99.2% of samples with regional variations in contamination levels. However, total aflatoxin concentrations remained within acceptable limits (10 ppb by UNBS; 20 ppb by FDA-USA; 15 ppb by FAO/WHO). A weak positive correlation between moisture content and aflatoxin levels was obtained, suggesting contamination may have occurred during drying. Despite regulatory compliance, widespread contamination highlights the need for improved post-harvest practices and continued aflatoxin surveillance in foods to safeguard public health.