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Explore this issueJune/July 2012
When a crisis emerges in our food supply—whether it is a foodborne illness outbreak, a recall due to the presence of an allergen, or identification of unwanted contaminants in imports/exports—consumers become concerned, and food producers and regulators are forced to respond quickly.
A typical response to a food safety crisis entails an uptick in product safety testing. Regulators, food producers, and technology companies all bear the responsibility of ensuring that the food safety test methods developed to identify potential contaminants are reliable, accurate, and robust.
The recent discovery of the fungicide carbendazim in orange juice samples imported to the United States from Brazil is one example of how a food safety concern made the development of new food testing methods necessary.
Carbendazim is a fungicide used to treat citrus trees in Brazil against diseases such as black spot. While this compound is approved for use in some countries, it is not approved by the U.S. Environmental Protection Agency for use on oranges. Given that the United States reportedly imports 15% of its orange juice supply, the majority of which comes from Brazil, the detection of this substance brought about an investigation in early 2012, culminating in a notice of action by the FDA for increased testing of orange juice shipments to the U.S. and throughout the world.
With the call to action for increased orange juice testing, food testing labs were tasked with quickly developing a method of analysis. Although this task seems straightforward, the method requirements are quite stringent.
The method must be accurate: How true is the value of contaminant identified in the sample? The method must be precise: Will you get the same results for multiple analyses of the same sample? The method must be selective and specific: Is what you are identifying as carbendazim actually carbendazim? The method must be robust: Will you get the same results hour after hour, day after day, regardless of small changes in external conditions? The method must be adequately sensitive: Are you able to detect the compound at concentrations relevant to the demands of global importing and exporting? All of these components funnel into one main characteristic—reliability: Are you sure your positive samples are actually positive and your negative samples are actually negative?
All of these requirements must be achieved within a very short turnaround time, an additional element of strain. For these reasons, scientists often employ advanced food testing technologies to get the job done. In the case of the analysis of carbendazim in orange juice, LC-MS/MS was the “go-to” method.
The Science of Crisis Response
When a food testing lab responds to a call to action, the method development process begins. Food safety labs place intense focus on the key method elements of accuracy, precision, specificity and selectivity, robustness, sensitivity, and, of course, reliability.
Method accuracy. Accuracy, measured against the result determined for an accepted reference material or standard, is sometimes difficult to address in food safety testing method development. Frequently, control or reference samples of the same type of interest—orange juice with a known amount of carbendazim, for example—are difficult or impossible to obtain. As a result, labs often use the standard additions approach (fortification of a negative control sample with the compounds of interest) to determine method accuracy.
In method development, accuracy measurements are typically the fundamental elements used to address method performance: Is the method efficiently extracting the compound of interest from the sample? Are additional sample cleanup steps required? Are the sample cleanup steps efficient? Are there interferences present from the matrix? It is not uncommon for a lab to go through multiple iterative changes in the sample preparation procedure before settling on a method with acceptable performance.