|
Food Protection Trends
Abstracts - January 2007
Effect of Cooling Rate on Pathogen Survival in Post-Process Contaminated Yogurt
Controlling Listeria monocytogenes in a Retail Setting
Effect of Cooling Rate on
Pathogen Survival in Post-Process Contaminated Yogurt
Kathleen A. Glass, Lindsey M. McDonnell, Rob C. Rassel, and Kristine L. Zierke
Food Research Institute, University of Wisconsin-Madison, 1925 Willow Drive, Madison, WI 53706, USA
SUMMARY
The effect of cooling rate on the survival of pathogens was
compared in full-fat and nonfat yogurt with strawberry fruit
preparation added (final pH 4.4). Products were inoculated with 4.5
log CFU/g of acid-adapted Listeria monocytogenes, Salmonella sp., or Escherichia coli O157:H7 and dispensed into yogurt cups. One set of
packages was immediately chilled to 7.2°C, whereas a parallel set of
packages was cooled from 27°C to 7.2°C within 96 hours, and then
both sets were stored at 7.2°C for the duration of the two-week
study. Triplicate samples of each treatment were enumerated by
standard plating methods at 24, 48, 72, 96, 168, 240, and 336 hours
storage. In yogurt cooled slowly, populations decreased 1.3 to 1.7
logs for Listeria, 2.2 to 3.0 logs for Salmonella, and 0.8-log for E. coli O157:H7 within 96 hours. In contrast, log reductions were 0.5 for
Listeria, 1.7 to 1.9 for Salmonella, and 0.2 to 0.3 log for E. coli O157:H7
in yogurt chilled immediately and held at 7.2°C for 96 hours. The pH
decreased in all yogurt treatments during the 2-week storage, but
the decrease was more rapid in the yogurt cooled slowly (final pH
4.1) than in samples chilled to 7.2°C immediately after inoculation
(final pH 4.2). These data support the safety implications of filling
yogurt with active cultures at 27°C followed by cooling to < 7.2°C
within 96 hours. To ensure a safe product to the consumer,
manufacturers should also comply with good manufacturing practices
and environmental controls.
Full Text Article
Controlling Listeria monocytogenes
in a Retail Setting
Dale A. Grinstead-1* and Catherine N. Cutter-2
1-JohnsonDiversey, 8310 16th St., Sturtevant, WI 53177
2-Dept. of Food Science, 202 Food Science Bldg., Pennsylvania State University, University Park, PA 16802
SUMMARY
Listeria monocytogenes (LM) is a deadly pathogen that sickens
approximately 2,500 people in the United States each year and has a
mortality rate of approximately 20%. The serious nature of the illnesses
caused by this organism makes control of LM in any food handling
environment important. Over the past decade, a vast amount of data
has been published about LM, including the illness it causes, the nature
of the organism, and its ecology. However, very little information has
focused on LM in a retail environment. Recent research has
demonstrated that LM is associated with a variety of ready-to-eat
foods produced in retail settings. It is likely to be found in the retail
environment, and there are many locations that could become
harborage points for the pathogen. The most effective way to control
LM in foods may be to keep the LM population to less than 100 cells
per gram of food. That means that it is important to control the
growth of this pathogen in food and in retail and other food handling
environments. Fortunately, there are some steps that can be taken to
help prevent LM from becoming established in a retail facility. These
steps include proper training of employees and operators, keeping
the retail environment as dry and clean as possible, maintaining
temperature controls, and ensuring that employees follow good
personal hygiene practices. Although L. monocytogenes is a dangerous
organism, it is possible to control the organism and minimize the
risks that it presents in a retail setting.
Full Text Article
|
