Multi-spectral kernel sorting to reduce aflatoxins and fumonisins in Kenyan maize

Abstract

Maize, a staple food in many African countries including Kenya, is often contaminated by toxic and carcinogenic fungal secondary metabolites such as aflatoxins and fumonisins. This study evaluated the potential use of a low-cost, multi-spectral sorter in identification and removal of aflatoxin-and fumonisin-contaminated single kernels from a bulk of mature maize kernels. The machine was calibrated by building a mathematical model relating reflectance at nine distinct wavelengths (470-1,550 nm) to mycotoxin levels of single kernels collected from small-scale maize traders in open-air markets and from inoculated maize field trials in Eastern Kenya. Due to the expected skewed distribution of mycotoxin contamination, visual assessment of putative risk factors such as discoloration, moldiness, breakage, and fluorescence under ultraviolet light (365 nm), was used to enrich for mycotoxin-positive kernels used for calibration. Discriminant analysis calibration using both infrared and visible spectra achieved 77% sensitivity and 83% specificity to identify kernels with aflatoxin > 10 ng g-1 and fumonisin > 1,000 ng g-1 , respectively (measured by ELISA or UHPLC). In subsequent sorting of 46 market maize samples previously tested for mycotoxins, 0-25% of sample mass was rejected from samples that previously tested toxin-positive and 0-1% was rejected for previously toxin-negative samples. In most cases where mycotoxins were detected in sorted maize streams, accepted maize had lower mycotoxin levels than the rejected maize (21/25 accepted maize streams had lower aflatoxin than rejected streams, 25/27 accepted maize streams had lower fumonisin than rejected streams). Reduction was statistically significant (p<0.001), achieving an 83% mean reduction in each toxin. With further development, this technology could be used to sort maize at local hammer mills to reduce human mycotoxin exposure in Kenya, and elsewhere in the world, while at once reducing food loss, and improving food safety and nutritional status.

Enhancing Food Safety through Adoption of Long-Term Technical Advisory, Financial, and Storage Support Services in Maize Growing Areas of East Africa

“…Sorting based on apparent moldiness was also found to reduce the percentage of contaminated samples by more than half [15]. To advance the safety through more efficient sorting, the LGPBS could work with scientists to validate and adopt multi-spectral sorters, as preliminary studies have shown that they can detect and sort both aflatoxin and fumonisin [64].…”

“…For example, although some interventions were found to reduce mycotoxin contamination at the experimental level, they have not been tested in actual field conditions. A promising technology like spectral sorting has been reported to work in the developing countries and was recently tested at laboratory level in Kenya [64]. Additionally, a recent study showed less aflatoxin in maize kernels of high density, but the potential of density-based sorters has not received adequate support to enhance evaluation [8].…”

Enhancing Food Safety through Adoption of Long-Term Technical Advisory, Financial and Storage Support Services in Maize Growing Areas of East Africa

“…To advance the safety through more efficient sorting, the LGPBS could work with scientists to validate and adopt multi-spectral sorters, as preliminary studies have shown that they can detect and sort both aflatoxin and fumonisin [55].…”

“…For example, although some interventions were found to reduce mycotoxin contamination at experimental level, they have not been tested in actual field conditions. A promising technology like spectral sorting has been reported to work in the developing countries, and was recently tested at laboratory level in Kenya [55]. Additionally, a recent study showed a less aflatoxin in maize kernels of low density, but the potential of density-based sorters has not received adequate support to enhance evaluation [9].…”

Thin Films Sensor Devices for Mycotoxins Detection in Foods: Applications and Challenges

“…Considering the agro-economic aspects and the impact on global agriculture, as well as the possible implications on the public health, the most relevant mycotoxins are aflatoxins (AFs), citrinin (CIT), deoxynivalenol (DON), fumonisin B1 (FB1), ochratoxin A (OTA), patulin (PAT), T-2 toxin (T-2), and zearalenone (ZEA) [3][4][5]. These toxins are found worldwide as natural contaminants in many food matrices of plant origin, like aromatic herbs, cereal grains, coffee beans, dried fruits, fruits, oilseeds, [60,61] ELISA-Enzyme-linked immunosorbent assay; GC-Gas chromatography; HPLC-FLD-High-performance liquid chromatography coupled with fluorescence detector; LC-MS-Liquid chromatography-mass spectrometry; TLC-Thin layer chromatography.…”