The US Food & Drug Administration announced their assessment of Salmonella risks associated with tree nuts in July 2013, and three years on, the work continues!
The purpose of the assessment is to “quantify the public health risk associated with the consumption of potentially Salmonella contaminated tree nuts”. FDA states that “the need for a risk assessment is underscored by outbreaks of human salmonellosis linked to tree nuts over the past decade, by product recalls, and by Salmonella isolation from tree nuts during surveys” (source).
…risk assessment [is] a methodical, quantitative approach to estimating the annual number of cases of illness arising from the consumption of a contaminated food by a population.
What is a risk assessment? It is a methodical, quantitative approach to estimating the annual number of cases of illness arising from the consumption of a contaminated food by a population. This requires a substantial amount of data on the prevalence (contamination rate) of the food in question, the size and number of servings consumed and the dose required to cause illness. Additional information is required on the fate and survival of the disease-causing organism (pathogen), including the concentration of organisms in the food, the effects of harvesting, storage and any lethality treatments (ex; roasting, steam pasteurizing, etc). This information is fed into a computer model to estimate the number of potential illnesses expected in the population.
An additional objective of the FDA study is to evaluate the impact of “risk-based” preventive controls on the incidence of illnesses traced to tree nut consumption. The FDA Tree Nut Risk Assessment was triggered in part by a request from the almond industry to have their mandatory 4-log Salmonella-inactivation treatment for domestically-shipped nuts be recognized by FDA as a pasteurization step. Despite the absence of mandatory requirements like the almond industry, other tree nuts are using lethality treatments on a voluntary basis. It is anticipated that the final FDA Tree Nut Risk Assessment will give them guidance on the log kill necessary to prevent cases of salmonellosis.
Over the past three years, a wealth of data has been submitted to FDA by the tree nut industry, and FDA themselves have collected over 4,000 retail samples for Salmonella testing. Some of these FDA tests triggered product recalls and substantial controversy within the tree nut industry. As of today the data sets for almonds, walnuts, pecans, pistachios and hazelnuts are largely complete, but major data gaps exist for Brazil nuts, cashews, chestnuts, macadamias and pine nuts. As the data collection continues to fill in this missing information, the work on the modelling the data and generating the risk assessment is nearing completion for some commodities. The almond risk assessment is nearly done, having completed an external peer review; it is currently scheduled to be released by the end of 2016. An external peer review of the pecan risk assessment is under way, and a computer model of Salmonella survival in almonds, walnuts, pistachios and pecans was recently published by FDA and is available online.
The tree nut industry eagerly awaits the final assessment reports, as they will be critical pieces of technical information to guide their food safety plans under FSMA. Will raw nuts still be an acceptable part of our daily diet, or will treatments to insure a 4 to 4 log kill of Salmonella be the new normal for the tree nut industry? Only time will tell!
