“Briefings from Dr. Bob Whitaker”

As passed on by Julia Stewart, the June 10 briefing from Dr. Bob Whitaker is posted on the PMA Web site here. Go to the PMA site for the complete transcript and audio recording, but here is one excerpt where Whitaker talks about how shippers can't "test their way" to food safety:

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.