to reduce the number of pathogens in
meat. High temperature treatments
are not suitable for sterilizing raw or
pre-cooked meats.
Thus techniques known as “cold
pasteurization” are used to enhance
the safety and extend the shelf life
of these products. Non-thermal treatments include chemical preservation
which is becoming less popular and
may not completely eliminate targeted
pathogens. Ionizing radiation (
irradiation) is approved for fresh poultry
in some countries and restricted in
others but is often met with negative
consumer perception in either case.
Microwaves have been shown to kill
many bacteria including E. coli,
salmonella and listeria.
Microwaves are non-ionizing form
of energy and thus they are not subject to
the same negative perception associated
with irradiation. It was initially thought
that the bactericidal effect of microwaves was only due to the heating effect.
However, recent studies have found
bacteria are inhibited using microwave
energy above the frequencies used to
produce heat by molecular friction.
The effect of heat
In the current study, researchers
first determined the effect heat contributed to killing E. coli and Staph.
aureus when the bacteria were exposed
to microwaves. They found that when
the temperature was held at or below
45 C, the heating effect on killing these
bacteria was virtually zero. Subsequent
experiments used a frequency of 18
GHz and power settings of 6 watts or 16
watts. Based on preliminary tests, 16
watts was found to be more effective.
Thus exposure times were set to
maintain the temperature below 45
C using 16 watts of power and one to
three exposures were used to maintain the needed temperature. Over
95 percent decontamination rate was
reported for three exposures of 52
seconds for both bacteria tested. Other
research has shown that higher microwave frequencies affect bacteria and
not muscle cells while lower frequencies have a greater effect on human
muscle and nerve cells. This implies
that higher frequencies might be useful
in inactivating bacteria while having a
minimal effect on meat quality.
Comment: These findings are
encouraging in that another tool to
inactivate pathogenic bacteria might
be available to the meat industry.
However, the decontamination levels of
less than 99 percent are in the 1-2 log
range so while 95 percent decontamination sounds impressive, more studies
are needed to increase this inactivation
rate to the 3-4 log range.
Shamis, Y., Taube, A., Shramkov, Y., Mitik-Dineva,
N., Vu, B., and Ivanova, E.P. 2008. Development
of a microwave treatment technique for bacterial
decontamination of raw meat. International Journal
of Food Engineering Volume 4, Issue 3, Article 8.
http://www.bepress.com/cgi/viewcontent.cgi
Omega- 3 fatty
acids in free-
range chicken
Consumption of foods containing
relatively high levels of omega- 3 fatty
acids has been associated with a reduced risk of cardiovascular disease.
Food companies are expanding into the
“functional” food market. Omega- 3 fatty
acids are a natural component in food
falling in the functional food category.
The omega- 3 fatty acids, specifically,
DHA may help reduce the risk of heart
disease, inhibit the growth of tumors
and deficiencies found to be associated
with ADHD, Alzheimer’s, depression
and other cognitive disorders. The fatty
acids have been incorporated into ani-
