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

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 (470–1550\ua0nm) 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 ultra-violet light (365\ua0nm), 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\ua0ng\ua0g and fumonisin >1000\ua0ng\ua0g, 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\ua

Near infrared spectrometry for rapid non-invasive modelling of Aspergillus-contaminated maturing kernels of maize

Aflatoxin-producing Aspergillus spp. produce carcinogenic metabolites that contaminate maize. Maize kernel absorbance patterns of near infrared (NIR) wavelengths (800-2600 nm) were used to non-invasively identify kernels of milk-, dough- and dent-stage maturities with four doses of Aspergillus sp. contamination. Near infrared spectrometry (NIRS) spectral data was pre-processed using first derivative Savitzky-Golay (1d-SG) transformation and multiplicative scatter correction on spectral data. Contaminated kernels had higher absorbance between 800-1134 nm, while uninoculated samples had higher absorbance above 1400 nm. Dose and maturity clusters seen in Principal Component Analysis (PCA) score plots were due to bond stretches of combination bands, CH and C=O functional groups within grain macromolecules. The regression model at 2198 nm separated uninoculated and inoculated kernels (p < 0.0001, R-2 = 0.88, root mean square error = 0.15). Non-invasive identification of Aspergillus-contaminated maize kernels using NIR spectrometry was demonstrated in kernels of different maturities

In vitro experimental environments lacking or containing soil disparately affect competition experiments of Aspergillus flavus and co-occurring fungi in maize grains

ABSTRACT: In vitro experimental environments are used to study interactions between microorganisms, and to predict dynamics in natural ecosystems. This study highlights that experimental in vitro environments should be selected to match closely the natural environment of interest during in vitro studies to strengthen extrapolations about aflatoxin production by Aspergillus and competing organisms. Fungal competition and aflatoxin accumulation were studied in soil, cotton wool or tube (water-only) environments, for Aspergillus flavus competition with Penicillium purpurogenum, Fusarium oxysporum or Sarocladium zeae within maize grains. Inoculated grains were incubated in each environment at two temperature regimes (25 and 30°C). Competition experiments showed interaction between the main effects of aflatoxin accumulation and the environment at 25°C, but not so at 30°C. However, competition experiments showed fungal populations were always interacting with their environments. Fungal survival differed after the 72-h incubation in different experimental environments. Whereas all fungi incubated within the soil environment survived, in the cotton wool environment none of the competitors of A. flavus survived at 30°C. With aflatoxin accumulation, F. oxysporum was the only fungus able to interdict aflatoxin production at both temperatures. This occurred only in the soil environment and fumonisins accumulated instead. Smallholder farmers in developing countries face serious mycotoxin contamination of their grains, and soil is a natural reservoir for the associated fungal propagules, and a drying and storage surface for grains on these farms. Studying fungal dynamics in the soil environment and other environments in vitro can provide insights into aflatoxin accumulation post-harvest

Aflatoxin Contamination of Maize, Groundnut, and Sorghum Grown in Burkina Faso, Mali, and Niger and Aflatoxin Exposure Assessment

Aflatoxin contamination of staple crops by Aspergillus flavus and closely related fungi is common across the Sahel region of Africa. Aflatoxins in maize, groundnut, and sorghum collected at harvest or from farmers&rsquo; stores within two weeks of harvest from Burkina Faso, Mali, and Niger were quantified. Thereafter, aflatoxin exposure values were assessed using per capita consumption rates of those crops. Mean aflatoxin concentrations in maize were high, 128, 517, and 659 &micro;g/kg in Mali, Burkina Faso, and Niger, respectively. The estimated probable daily intake (PDI) of aflatoxins from maize ranged from 6 to 69, 29 to 432, and 310 to 2100 ng/kg bw/day in Mali, Burkina Faso, and Niger, respectively. Similarly, mean aflatoxin concentrations in sorghum were high, 76 and 259 &micro;g/kg in Mali and Niger, respectively, with an estimated PDI of 2&ndash;133 and 706&ndash;2221. For groundnut, mean aflatoxin concentrations were 115, 277, and 628 &micro;g/kg in Mali, Burkina Faso, and Niger, respectively. Aflatoxin exposure values were high with an estimated 9, 28, and 126 liver cancer cases/100,000 persons/year in Mali, Burkina Faso, and Niger, respectively. Several samples were extremely unsafe, exceeding manyfold regulatory levels of diverse countries (up to 2000 times more). Urgent attention is needed across the Sahel for integrated aflatoxin management for public health protection, food and nutrition security, and access to trade opportunities