Processing steps of peanut butter and increases risk of salmonella contamination

Heat Tolerance of Salmonella enterica Serovars Agona, Enteritidis, and Typhimurium in Peanut ButterAuthors: Shachar, Dina1; Yaron, Sima1
Source: Journal of Food Protection, Volume 69, Number 11, November 2006, pp. 2687-2691(5)

Abstract:
Recent large foodborne outbreaks caused by Salmonella enterica serovars have been associated with consumption of foods with high fat content and reduced water activity, even though their ingredients usually undergo pasteurization. The present study was focused on the heat tolerance of Salmonella enterica serovars Agona, Enteritidis, and Typhimurium in peanut butter. The Salmonella serovars in the peanut butter were resistant to heat, and even at a temperature as high as 90°C only 3.2-log reduction in CFU was observed. The obtained thermal inactivation curves were upwardly concave, indicating rapid death at the beginning (10 min) followed by lower death rates and an asymptotic tail. The curves fitted the nonlinear Weibull model with β parameters <1,>

TAINTED PEANUT BUTTER TRAIL EXPLAINED

June 1/99
UPI
By ED SUSMAN
UPI Science News

Available online:http://www.marlerblog.com/2007/02/articles/legal-cases/officials-check-for-salmonella-tennessee-in-peanut-butter/

CHICAGOQ Peter Wood, senior lecturer in microbiology at Queensland
University of Technology, Brisbane, was cited as telling the annual
meeting of the American Society for Microbiology that they tracked a
continent-wide 1996 outbreak of salmonella poisoning that affected
hundreds of peopleQmainly childrenQto a failure to sanitize a rarely used
piece of machinery at a peanut roasting factory.
The story says that DNA testing made it possible to determine if people in
Perth on the Indian Ocean or in Sydney on the Pacific Ocean had diarrhea
and other gastrointestinal illnesses because of the same strain of S.
Mbandaka bacteria.
Wood was cited as saying that researchers first suspected people were
infected through disease-carrying chicken, but after a while it became
evident peanut butter sandwiches might be a culprit as well. Previously,
Wood said he was unaware of peanut butter being involved in salmonella
outbreaks.
Microbiologists traced the salmonella to a particular brand of peanut
butter from a manufacturer in Queensland.
Wood was quoted as saying, "Fortunately, the company had retained a sample
of that batch of peanut butter so that shelf life tests could be
conducted," and that the sample was contaminated with the same strain of
S. Mbandaka infecting patients.
The batch of peanut butter was traced to one batch of roasted peanuts from
one supplier. Again, the disease detectives were in luck, because the
supplier had kept a sample of the peanuts to study possible aflatoxin
contamination. Again tests matched the strains of salmonella.
It turns out that the roasting company had moved and separated the roasted
peanuts with an auger, a drill-like machine with a spiraling blade that
could lift piles of peanuts.
Wood was quoted as saying, "The auger was only used four times because it
proved not to be as time-saving as first thought."
Wood said the machine was rarely used and had been kept in the company
tool yard. During that time, eastern Australia was in the throes of a
plague of mice. The rodents nested everywhere, including the tool yard,
where their droppings contaminated the auger.
When the auger was brought in to the plant, it was washed down but Wood
said it was not sanitized before it was used on Jan. 10, 1996.
Salmonella from the auger became mixed with the peanuts, and the
contaminated peanuts in turn contaminated the peanut butter production
apparatus. Jar after jar of contaminated peanut butter began wending its
way to supermarket shelves under generic labels.
Wood was quoted as saying, "It took us six months to track down the cause
of the outbreak," and that over that time, peanut butter production had
continued, meaning all six months' worth of peanut butter had to be
removed from store shelves and destroyed.
He said the company fully cooperated in recalling $50 million worth of
product. Wood did not identify the producer.

Source: Brenda Frohloff , Peanut Butter Recall: Mystery Solved, April 10, 2007

Available online: http://www.lawyersandsettlements.com/articles/00738/peanut-butter-mystery.html

Salmonella is routinely found in the soil in which peanuts are grown, but the process of roasting peanuts and further heating them above 165 degrees when they are ground to make peanut butter kills any salmonella bacteria. Following the mixing process, the peanut butter is squirted into containers, cooled and sealed. However, in ConAgra's Georgia plant, enough salmonella bacteria got into open containers of freshly made peanut butter to contaminate them before they were sealed.

Burnett et al. Survival of Salmonella in peanut butter and peanut butter spread. J Appl Microbiol. 2000 Sep; 89(3):472-7.

Available online: http://www.highlighthealth.com/health-news/peanut-butter-recalled-due-to-salmonella-outbreak/

In 1996, the first and only known outbreak of Salmonella associated with peanut butter was reported in Australia and blamed on unsanitary plant conditions. During the process of making peanut butter, the nuts are heated to temperatures above 165 °F (74 °C), sufficient to kill Salmonella. However, after the heating step there are a number of opportunities for contamination. A 2000 study to determine the survival characteristics of Salmonella in peanut butter showed that, depending upon formulation, post-process contamination may result in bacterial survival in the product for the duration of the shelf life at 41 °F (5 °C) and possibly 70 °F (21 °C) .