An Interesting Article in Science News Online

[Joel Baumbaugh <baumbaug@nosc.mil>]

	I thought that this article was interesting because it combined
irradiation with sorbic acid to obtain basically the same result as and
"excess" of one or the other - well, just read the article (grin)...jb

	Joel Baumbaugh (baumbaug@nosc.mil)
	SSC-SD 

June 12, 1999 

                              
    Irradiated Ice Cream and Cake

The home baker usually doesn't have to
worry much about spoilage in
pies and cakes. They don't last long
enough to go bad.

For commercial bakeries that ship their
pastries and other confections,
fungi can put a serious dent in the
bottom line. It can take nearly a week
to move breads, fresh cakes and other
baked goods across country. By
the time the goodies hit grocery shelves,
unappetizing colonies of mold
may already be evident.

In Bombay, India, where microbiologist
Rahul Warke works, the tropical
climate and frequent lack of
refrigeration conspires with molds and bacteria to blight foods even
faster. When a commercial U.S. bakery
approached Warke's team at the University of Bombay
asking for help in extending the shelf
life of its products, one suggestion immediately jumped to
mind: irradiation.

Manufacturers often use sorbic acid (also
noted as sorbate on the package) as a mold-retarding
agent. To pack a truly powerful punch,
however, bakeries need to add quite a bit—enough that
discerning consumers may complain about
an objectionable aftertaste.

The same thing is true of irradiation.
Pump gamma rays through a fat-filled confection to kill all the
microbes present and those fatty lipids
will oxidize, creating a rancid taste.

What Warke's team did was marry the
two—sorbic acid and food irradiation—so that low doses of
each would be sufficient. Applying low
doses of the chemical preservative (0.2 percent by weight)
and of irradiation (1 kilogray or less)
protected cakes "amazingly," Warke reported at the American
Society for Microbiology meeting last
week in Chicago. "With this combination treatment," he told
Science News Online, "we could increase
the shelf life of a cake from just 7 days to almost 4
months."

His group, which is patenting the combo,
says bakeries have shown significant interest in
commercializing the technology.

                  The cold truth—a cone of germs

At the meeting, Warke also reported data
from a survey that his team conducted of ice cream
purchased in and around Bombay. Many
samples of the frozen treats contained common, potentially
life-threatening foodborne pathogens,
such as Listeria and Yersinia.

Nor are germ-ridden ice creams a problem
only in developing countries. Federal epidemiologists
traced the largest salmonella outbreak
ever recorded in the United States to contamination of a
nationally distributed ice cream (see
related story).

Standard means of sterilization—chemical
treatments or heating—aren't an option for foods that
should remain ­70°C to ­90°C. So, how's a
manufacturer to kill any freeloading microbes that may
have stowed away in a gallon of creamy
dessert? Again, Warke recommends irradiation.
Previously, researchers had zapped frozen
snacks with 40 kilograys of X rays. However, as with
cakes, that heavy dose of radiation
oxidized the fats that give rich ice creams their velvety taste.
"So, we've turned to really low doses,"
Warke says, "in the range of between 1 kilogray and 2
kilograys."

In tests with strawberry and chocolate
ice creams, the researchers found that the irradiation killed
germs but left no aftertaste. Indeed,
they could up the dose to 5 kilogray with no flavor deterioration.
Not so with vanilla. Except at the lowest
of the tested doses, taste panels could pick up flavor minor
changes.

Tobacco is another solid candidate for
low-dose irradiation, Warke believes. "People have no idea
how much bacteria and fungi they can
ingest from chewing tobacco," he says. He has sometimes
measured heavy microbial contamination in
this product. "I have studied the process under which it
is manufactured, and it doesn't really
have any checks for bacterial or fungal counts," he says.

Because some fungi have been linked to
the development of oral and gastric cancers, he notes,
tainted tobacco could prove a risk factor
for more than just gut-wrenching food poisoning. "But when
we used irradiation, it worked," killing
off the potentially pathogenic microbes, he says.

Currently, Warke observes, irradiation is
not approved for any of these proposed applications-in the
United States or India. However, with the
safety and efficacy studies that are now underway, he
says, that may change.

                                  Further Readings:

Warke, R.G., A. Kamat, P. Thomas,
and M.Y. Kamat, 1999. Enhancement in shelf life
and improvement of microbiological
quality of cakes and ice creams using low dose
irradiation (Abstract P69), American
Society for Microbiology annual meeting abstract
book, p. 524.

                                  Sources:

                                       Rahul Warke
                                       University of Bombay
                                 A-15 Megh Malhar
                                       Gavand Tath
                                       Naupada, Thane
                                       India

This Food for Thought was prepared by
Janet Raloff, senior editor of Science News.

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