Can’t I just test my product to prove it is safe?
Hello, this is PMA Public Relations Director Julia Stewart, and welcome back to PMA’s new briefing series, “Ask Dr. Robert Whitaker.” This is our second installment in a series about food safety, science and innovation.
Before we get to today’s topic, we would like to take this opportunity to briefly update our listeners on the latest developments regarding the tomato foodborne illness outbreak that is gripping the nation. The Food and Drug Administration has not yet been able to specifically identify the source of the affected tomatoes – although they have been able to exclude a number of products and producing regions. Meanwhile, retailers and foodservice operators are pulling all tomatoes from their shelves and menus – even tomatoes that have been deemed safe.
Please know that PMA and our tomato industry allies are doing everything we can to speed FDA’s traceback. While we are not apologists for FDA, they believe they are acting in the best interests of public health. We also must, and do, put public health first. But at the same time, PMA and other tomato industry leaders have made it abundantly clear to FDA that we expect a speedy resolution to their traceback process – and that the entire tomato industry’s livelihood is at stake.
Now to today’s briefing. Bob, one PMA member who is following the salmonella saintpaul illness outbreak that has been linked to certain types of tomatoes has asked us …
Can’t I just test the product I have in my warehouse, to prove that it is safe?
Dr. Whitaker:
Sure, Julia, but first I’d like to let our listeners know that I’m already working on our next briefing, which will address the question of why FDA’s traceback process takes so long, so stay tuned for that topic.
Now to testing: Any producer can certainly develop a testing program for either raw or finished products – but it is important to understand what the testing data means, and more importantly to know what it does not mean.
To set up a testing program, first it is important to find a certified laboratory that uses FDA and/or AOAC-approved methodologies for measuring pathogens. It is important to understand their test procedures, the handling practices their laboratory set up, and how the data will be reported and to whom. It is also important to remember that testing takes time. You will need to incorporate this time requirement into your logistical programs – for example, if you are testing raw product prior to harvest, you will need to schedule testing in advance of harvest so that you can get the results back before you start the harvest. If you are testing finished products, you will likely want to “hold” the finished products until you have the results from the testing in hand. This can take 24-48 hours or more depending on methods used and results. You will likely want to “hold” the products because if you ship them and then receive a positive test result, you will have to recover or recall those products – and incur the costs and potential publicity that would entail. Besides the time lost on your product’s “shelf life,” you will also need the storage space to hold finished products prior to receipt of the testing and clearing the products for shipment, and be willing to incur those related storage expenses.
Once you understand the issues related to testing programs, as if that wasn’t complex enough, then you move to the more difficult issue of sampling. This is where perception needs to come to grips with reality, folks.
If a producer had a large, wide-spread contamination – let’s say the water used for rinsing the harvest totes was contaminated – sampling of raw product post-harvest may indeed detect the contamination, and the unsafe product could be destroyed. But absent a large or catastrophic event, the general feeling in the scientific community is that the contaminations that lead to foodborne illness outbreaks are at low levels and not widely spread – for example, all it takes is a single ill worker that did not wash his or her hands properly after using a restroom, and Now lets say that worker handles perhaps a few hundred fruit out of millions processed by a given facility daily. Because it only takes a very low level of contamination to make people sick, we are then challenged to determine how many tomatoes or leafy greens samples or melons, et cetera that we would have to sample and test to be sure that we could find every fruit or leaf that was contaminated by our ill worker to keep them from reaching consumers. We can’t test every tomato, that is too expensive – and you end up with no fruit to sell because you had to destroy it all to test it.
Instead, you need to rely on statistical sampling to have confidence that you can eliminate any tomato that is contaminated. But because we believe that contamination events happen so infrequently and at low levels, there simply is not a satisfactory statistical solution to the problem. You can’t just take 20 or 30 tomatoes from a harvest of a thousand and sample them, get a negative result and expect that the remainder of the product is free of pathogens.
Here’s why: Let’s say there are a thousand tomato plants in a block for harvest. Let’s also say that we are going to harvest 20 fruits from each plant over the next 3 weeks; so 60,000 total tomato fruits will come out of that single block. Now let’s say that somehow during the harvest period, 200 fruits have become contaminated with a very low level of Salmonella. You have all your tomatoes in boxes; how do you sample to be sure you can eliminate those that are contaminated? Try it another way, imagine trying to pick 200 black marbles out of a huge box of 60,000 white marbles – and do it blindfolded to boot, because remember, you can’t see bacteria like salmonella. How many times would you have to “sample” the box to get all 200 black marbles? It is a daunting question and given the time, cost and the fact that the test is destructive, it is not practical.
So while the perception of product testing for pathogens on products sounds great, in reality it is currently too difficult to do with any acceptable sense of credibility. You are better off spending your resources to prevent contamination in the first place by having rigorous and frequently reviewed risk-based food safety programs in place.
Julia:
Please join us again next time, when Bob will talk about why traceback can be such a lengthy process. And if you would like to submit a question, email it to us at foodsafety@pma.com. Goodbye for now!