Mycotoxin Development in Cashew Apple-Wheat Flour Composite During Tropical Storage

Valorisation of cashew apples (Anacardium occidentale L.) offers an opportunity to address food waste in Ghana, where approximately 90% of these edible fruits remain unutilised despite the country's position among global leaders in cashew production. This study examined the development of mycotoxins in cashew apple-wheat composite flour systems during ambient tropical storage (25°C ± 2°C, 65 ± 5% RH) over 14 days. Three composite flour formulations were prepared for subsequent bread production, with cashew apple flour substituting wheat flour at 5%, 10%, and 15% (w/w) levels. The storage stability of these pre-mixed flour blends was evaluated, as they represent the critical phase when processors store prepared formulations prior to baking. Monitoring of moisture content, fungal growth, and aflatoxin B1 levels was conducted using standardised AOAC and ISO methods. An increase in moisture was observed across all formulations, with the 5% substitution reaching a moisture content of 13.21% by day 14. Fungal populations increased exponentially (10²-10⁴ CFU/g) and showed a strong positive correlation with moisture content (r = .87, P < .001). Aflatoxin B1 was detected on day 7, rising to 8.7 μg/kg in the 5% formulation by day 14, exceeding European Union safety limits (2 μg/kg) for cereal-based products. However, higher cashew apple substitution (15%) demonstrated dose-dependent antimicrobial effects, resulting in significantly lower fungal counts (6.8 × 10³ CFU/g) and aflatoxin levels (4.1 μg/kg), likely due to naturally occurring phenolic compounds and other bioactive substances. While incorporating cashew apple flour offers considerable potential to reduce food waste and enhance nutrition, the current formulations pose unacceptable food safety risks under uncontrolled tropical storage conditions. For commercial viability, strict moisture control (⩽13%) and temperature regulation are essential to meet international food safety standards.