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A Ratio Process Makes It Easier To Detect Aflatoxin Levels

By Sarah Tarshis
July 12, 1999

One bad nut can spoil the whole bunch, thanks to aflatoxin, a carcinogen that can contaminate peanuts and other commodities. Federal food safety regulations create a need to find the most efficient aflatoxin detection method possible. Such methods can be time-consuming and expensive.

So Thomas B. Whitaker of the Agricultural Research Service has been researching methods of accurately estimating aflatoxin levels in peanut lots to better ensure appropriate handling. He developed a new method of detection that may reduce economic loss for handlers and farmers while also preserving quality.

Whitaker’s method of detecting aflatoxin in a lot is to measure the aflatoxin levels in the high-risk peanuts. Peanuts that are damaged, loose shelled or small are labeled high-risk. An estimated ratio of aflatoxin in high-risk peanuts to aflatoxin in the lot determines the aflatoxin of the entire lot. Whitaker found that a five-to-one ratio accurately assesses the aflatoxin levels. For example, if a high-risk sample has an aflatoxin contamination level of 100 parts per billion (ppb), the entire truckload will probably average 20 ppb--the Food and Drug Administration’s legal limit for food quality safety. The ratio was derived over a wide range of concentration in many lots, according to Whitaker.

The current method of detecting aflatoxin in peanuts can cause farmers and handlers to lose profits because of inaccuracy. When a truckload of peanuts is brought from a farm to the buyer, it is sampled and visually examined for moldy kernels that indicate the lot may be contaminated by aflatoxin. If even one moldy kernel is found, the entire truckload is classified as a low-grade status that could result in profit loss. The ratio method might be used to replace or complement the current method of visual analysis.

A story on the research is in the July issue of Agricultural Research magazine and on the web at:


Scientific contact: Dr. Thomas B. Whitaker, ARS Market Quality and Handling Research Unit, Raleigh, N.C.; phone (919) 515-6731, fax (919) 515-7760,

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