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Dairy, Food and Environmental Sanitation
Abstracts - September, 2000
- The Effect of Different Thawing Methods on the Growth of Bacteria in Chicken
- Small Round Coliphages as Surrogates for Human Viruses in
Process Assessment
The Effect of Different Thawing Methods on the Growth of
Bacteria in Chicken
S. M. Jiménez,1 M. E. Pirovani,1 M. S. Salsi,1 M. C. Tiburzi,1 and O. P. Snyder2
SUMMARY
Frozen raw chickens were thawed by three different methods to study population changes of spoilage bacteria and
of Salmonella hadar during thawing. It was shown that thawing chicken on the counter at ambient temperature (21°-22°C)
within 14 hours or less, to an internal temperature of 4.4°C (3.5 cm within the breast), is a safe procedure,
as evidenced by a decline in bacterial population; that thawing chicken in flowing water is a safe, rapid method,
and that thawing chicken in a standard refrigeration unit (at a temperature of 3.5° to 7.2°C) is also a
safe method. However, this experiment indicates that the longer time period required to thaw chicken at refrigeration
temperatures to an internal temperature of 4.4°C (3.5 cm within the breast) permits growth of pseudomonas spoilage
bacteria.
The population of Salmonella hadar inoculated onto the surface of chicken carcasses prior to freezing was shown
to have decreased by the end of all thawing methods, when thawing was halted at 4.4°C.
Most regulatory agencies follow FDA recommendations, which do not allow food to be thawed at ambient temperature.
The FDA retail food code recommends that food be thawed under refrigeration, or in flowing water, so that the temperature
of the food does not exceed 5°/7.2°C (41°/45°F). The USDA has no restriction regarding how food
is thawed, even when food is thawed at ambient temperature.
Because of small sample size, it is difficult to draw major conclusions. However, this study tends to confirm that
controlled thawing at ambient temperatures, as permitted by the USDA, does not lead to increased hazards.
Small Round Coliphages as Surrogates for Human Viruses
in Process Assessment
Tadesse W. Mariam2 and Dean O. Cliver1
SUMMARY
Inactivation of hepatitis A virus (HAV) was compared with inactivation of the small round RNA (MS2) and DNA (fX174)
coliphages and, in some instances, poliovirus 1. The processes tested (heating in tap water and milk, air drying
on a surface, and ClO2 disinfection of water and strawberries) are applicable to food and water. The poliovirus,
where tested, was always more labile than HAV. Inactivation of MS2 showed some similarity to that of HAV during
heating in water and milk, especially at 72°C. HAV was considerably more resistant than either coliphage to
drying and to ClO2 disinfection. Even though the coliphages were usually less resistant, they might be useful surrogates
for HAV in pilot-scale studies if reliable conversion factors could be established.
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