Abstract
An attempt was made to compare between easy and inexpensive qualitative method (ammonia vapour test) and analytical methods (thin layer chromatography and enzyme-linked immunosorbent assay) for identification of aflatoxigenic isolates of Aspergillus flavus in maize. In this comparative study the toxicity level of A. flavus isolates exhibited 100% agreement among ammonia vapour test, ELISA and TLC for highly toxigenic (>2000 ppb) and toxigenic (501–2000 ppb) isolates while 88.5% agreement observed for least toxic (<20 ppb) isolates. In ammonia vapour test 51% of A. flavus isolates showed creamish or no colour change corresponding to least toxic/atoxic (<20ppb) category estimated by ELISA. Similarly 22% highly toxic isolates exhibited plum red colour, 12% moderately toxic indicated pink colour and 10% toxic isolates showed red colour. However, 11.5% isolates were found to be false positive in cream colour category (least toxic) and 28.5% false negatives in pink colour (moderately toxic) category. The isolates from different agroclimatic zones of maize in India showed high variability for aflatoxin B1 (AFB1) production potential ranging from 0.214–8116.61 ppb. Toxigenic potential of Aspergillus flavus isolates in culture was further validated by inoculating maize grain sample with four different isolates with varied toxin producing ability. With good agreement percentage between cultural and analytical methods the study concludes the ammonia vapour test to be easy, inexpensive, reliable and time saving method that can be used for segregating or pre-screening of contaminated samples from bulk food/feed stock.
Highlights
Aflatoxins are naturally occurring mycotoxin and outrageous contaminants of the important agricultural commodities such as corn, peanuts, pistachio, Brazil nuts, oilseeds like cottonseed and copra [1, 2, 3].Exposure to aflatoxins causes both acute and chronic risks to lower income populations in tropics mainly consuming large quantity of maize or groundnut as staples
Screening of aflatoxin production potential in cultures of A. flavus isolates showed 52% of isolates with very low concentration of aflatoxin B1 (AFB1) (
The detection of 28.5% of false negative in pink category signifies that the aflatoxin producing ability of isolates estimated by enzyme linked immuno- sorbent assay (ELISA) falls in 21-500ppb category but the corresponding colour of ammonia vapour test didn’t coincides with the respective category i.e., pink colour
Summary
Aflatoxins are naturally occurring mycotoxin and outrageous contaminants of the important agricultural commodities such as corn, peanuts, pistachio, Brazil nuts, oilseeds like cottonseed and copra [1, 2, 3].Exposure to aflatoxins causes both acute and chronic risks to lower income populations in tropics mainly consuming large quantity of maize or groundnut as staples. Aflatoxicosis may lead to cancer and immune suppression and in acute condition may cause death [4]. In India, during 1974 an outbreak of hepatitis caused many deaths attributed to the consumption of heavily aflatoxins contaminated maize [5]. It is well established that chronic exposure to aflatoxins leads to liver cancer (especially where hepatitis is prevalent), and this is estimated to cause as many as 26,000 deaths annually in Africa and south of the Sahara. Aflatoxin contamination is one of the most challenging and serious food safety problem worldwide, to establish control measures extensive research work is being done in this area. Growth of commercial markets for food and feed, including exports is affected by aflatoxin contamination [6]
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