Evaluation of the bright greenish yellow fluorescence test as a screening technique for aflatoxin-contaminated maize in Malawi

Abstract

The bright greenish yellow fluorescence (BGYF) test has been used with varying success in screening for aflatoxins in maize. This test was applied to 180 maize samples collected from different markets within 12 districts of Malawi in order to evaluate its performance against high performance liquid chromatographic analysis. The number of BGYF grains in 2.5 kg unground samples ranged from 0 to 35 and about 49% of all tested samples had aflatoxin ranging from 1 to 382μg/kg. A total of 65(36%) of the examined unground samples showed no BGYF. The European Commission (Decision 2002/657/EC) recommends a false negative rate of less than 5%, for a screening technique to be acceptable. In this study, 4 BGYF grains per 2.5 kg unground maize sample successfully indicated aflatoxin contamination of >10 μg/kg (COMESA maximum tolerable limit), with a 4.4% false negative rate. In this case, the amount of confirmatory analyses would be reduced by 63%, if the BGYF test was employed as a screening method. The screening technique therefore offers a practical screening tool for Malawi and possibly for the sub-Saharan region.Keywords: Maize, aflatoxin, BGYF, screening, Malawi IntroductionMaize is the most important food crop in Sub-Saharan Africa. In Malawi, it contributes significantly to the diet of more than 80% of the population (Pingali, 2001). In this context, contamination of maize with mycotoxins, mainly aflatoxins, is a matter of concern for food quality control (Matumba et al., 2009). Aflatoxins are toxic secondary metabolites produced by several species of filamentous Aspergillus, including A. flavus, A. parasiticus and A. nomius on a wide variety of food matrices. They are immunosuppressant, mutagenic, teratogenic, carcinogenic and cause growth retardation in humans and animals (IARC, 1993;Khlangwiset et al., 2011;Preisler et al., 2000;Wangikar et al., 2005) and as such, aflatoxins are regulated world-wide (Van Egmond et al., 2007).The presence of aflatoxins is determined by rapid presumptive and screening tests after which positive results are confirmed using chromatographic techniques such as high-performance liquid chromatography (HPLC) with fluorometric detection, liquid chromatography with mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS) (Anklam et al., 2002; EC, 2002;Shephard, 2009). However, confirmatory tests are expensive and often unavailable in most developing countries, such as Malawi. The use of screening techniques reduces the number of samples that must be tested using confirmatory methods and thus reduces the cost of analyses. Unfortunately for the developing world, available screening techniques (e.g. ELISA) are still expensive, not readily available and often require special storage such as refrigeration for antibodies (Goryacheva and Saeger, 2011).The presence of bright greenish yellow fluorescence (BGYF) is used as a presumptive test (black light test) to identify maize lots that may contain aflatoxins. Basically, the BGYF test involves inspection of samples under a "black" o...

Uncommon occurrence ratios of aflatoxin B1, B2, G1, and G2 in maize and groundnuts from Malawi

“…Although a significant proportion of the aflatoxin positive samples included in the study originated from the mid-elevation agro-ecological zone (22.5 %), it is worth noting that this does not reflect the aflatoxin prevalence in the zone as at all times, the majority of the samples that were tested were collected from the mid-elevation which is the main maize and groundnuts-producing area in Malawi. In fact, the aflatoxin problem is more prominent in the lower Shire and the lake shore, middle, and upper-Shire agro-ecological zone than in the midelevation and highlands (Matumba et al 2013;Matumba et al 2014b).…”

“…In fact, the European Commission (Decision 2002/657/EC) calls for a ≤5 % false-negative rate for a screening technique to be acceptable (European Commission EC 2002). Previously, Matumba et al (2013) reported to have successfully screened shelled maize using the presence ≥four bright greenish-yellow fluorescence (BGYF) grains per 2.5-kg maize sample as an indicator for total aflatoxin >10 μg/kg with a 4.4 % falsenegative rate.…”

Provitamin A Carotenoids in Grain Reduce Aflatoxin Contamination of Maize While Combating Vitamin A Deficiency

“…The extent of A. flavus invasion in maize grain was assessed using the bright greenish yellow fluorescence (BGYF) test (Busboom and White, 2004; Matumba et al, 2013). After shelling and drying (as described above), 100-kernel random samples were taken for each plot.…”

Keeping mycotoxins away from the food: Does the existence of regulations have any impact in Africa?

“…Although there has been a gradual improvement, sub-Saharan Africa has been persistently ranked highest in human undernourishment worldwide with rates estimated between 31% in and 25% in 2011-2013(FAO, IFAD and WFP, 2013. Given the clear evidence of food shortage and high incidence of mycotoxin in food in Africa (Matumba et al, 2014;Adetunji, et al, 2014;Ediage et al, 2014;Mohale et al, 2013;Matumba et al, 2013;Lewis et al, 1995), is there any room for reaching a compromise between achieving food sufficiency and food safety in Africa? …”