There is no such thing as zero risk when it comes to food safety, according to researchers.

Joe Whitworth of Food Safety News, writes researchers Marcel Zwietering, Alberto Garre, Martin Wiedmann and Robert Buchanan presented the study, published in Current Opinion in Food Science, at IAFP Europe.

They defined residual risk as what remains even after a fully compliant food safety system has been implemented. Every product has a residual risk but severity varies because it depends on a variety of factors such as the perspective or consequences.

Researchers gave the example of the risk of Salmonella in chocolate bars assuming contamination of one Salmonella enterica cell per 10,000 of 25,000 bars of 25-grams, and that the company produces 100,000 bars a day. Testing is limited to five samples per day, each sampling unit is a whole bar, and probability of a false negative or false positive is zero.

“The probability of detecting Salmonella in each sampling unit equals 0.01 percent, and the probability of detecting it in the product in a given day is 0.05 percent. In other words, we expect a single positive every 5.5 years. On the basis of this result, it could seem reasonable to conclude that the risk of salmonellosis is insignificant.

“However, a single cell of Salmonella enterica has a probability of causing illness that has been estimated to be 1 case per 400. Therefore, if we consider that 10 bars of the 100,000 daily production contain a single Salmonella enterica cell, the expected number of yearly cases of salmonellosis is 9.125, a value that is certainly not insignificant. Although sampling will rarely show a positive, there is clearly a residual risk.”

Bill Leiss and I wrote a book on this topic, Mad Cows and Mother’s Milk, published in 1997, explicitly stating there is no such thing as zero risk: it’s about maximizing the benefits and minimizing the risks in food safety stuff.