poisoning can make you plenty sickand even lead to deathbut
help is on the way. Engineers are developing new technologies that can
destroy the deadly microorganisms that cause it.
By Alice Daniel
about the pressure at the deepest point in the Pacific, 36,000 feet
below the water's surface. Now multiply that not once, not twice,
but 10 times. It's mind-boggling to imagine, but if you're
a food-borne pathogen under the watchful eyes of engineers at Washington
State University, that's just the kind of stress you're under.
called ultra high pressure and it's one of many applications engineers
are experimenting with to kill deadly microorganisms and make food safera
task that is likely to be appreciated by anyone who has ever experienced
the sheer misery of food poisoning. According to the Centers for Disease
Control, 76 million Americans get sick, 325,000 are hospitalized, and
5,200 die annually from food-borne illnesses. Salmonella, Listeria,
and Toxoplasma account for the majority of deaths caused by known pathogens,
but it is the lethal strain of the bacteria E. coli (0157:H7) that is
ingrained in the public consciousness. In 1993, one high-profile outbreak
left four children dead and 700 people ill after they ate undercooked
hamburgers at Jack in the Box restaurants in the Northwest.
CDC states that the prevention of food-borne diseases is a major public
health challenge, one that Gustavo V. Barbosa-Cánovas, a professor
of food engineering and director of the Center for Nonthermal Processing
of Food (CNPF) at Washington State, takes seriously. He is one of the
engineers experimenting with such technologies as ultra high pressure,
a process that relies on a pump to generate enough pressure to kill
microorganisms without damaging the food. Food is placed inside a plastic
bag and then immersed in water inside a cylinder. A pump pressurizes
the water, which, in turn, pressurizes the food. There's
an equilibrium inside and outside the tissue of the food, explains
Barbosa-Cánovas. In fact, the difference between ultra high pressure
and conventional thermal processing techniques that use high heat to
destroy microorganisms is that the quality of the food is not adversely
affected by the high pressure technique.
ultra high pressure alone is not capable of destroying spores, which
evolve from bacteria and have a very thick outer layer. Spores might
be found in foods that have a high pH such as canned vegetables and
meats. The bacterium Clostridium botulinum is the number one enemy,
says Barbosa-Cánovas, because in spore form it can cause the
rare but deadly disease botulism. In such cases, heat is added to the
pressure, but not enough to adversely affect food quality.
promising applications to kill microorganisms have evolved out of medical
technologies. Ultrasound, for instance, destroys the basic functions
of the microorganisms when it is applied at very high frequencies. We're
rocking them so fast and so violently, they just collapse, says
Barbosa-Cánovas. He offers an interesting analogy when explaining
another process, pulsed electric-field technology: It is like
subjecting microorganisms to an electric chair with an extremely high
voltage. Ali Demirci, an assistant professor of agricultural and
biological engineering at Penn State, is using pulsed ultraviolet light
to kill microorganisms. By pulsing the light, the energy is intensified
and, therefore, more
effective in disabling deadly pathogens by inhibiting DNA functions.
There is a big future for this technology, says Demirci,
who developed the pulsed UV system thanks to a NASA grant. I have
great confidence that this is a very powerful
system. All we need is to find the right application.
Pass The Salt
of the earth, literally, might prove to be one of the most useful solutions
to treating food-borne pathogens when it is applied to the 17th-century
principle of electrolysis. The technique, electrolyzed oxidizing (EO)
water, generates both alkaline and acidic water by electrolyzing very
dilute salt water into sodium and chloride. The acidic water can be
used as a sanitizing solution to treat the surfaces of meats, fruits,
and vegetables. It kills food-borne pathogens effectively because of
the combination of a low pH, chlorine, and a high oxidation reduction
potential. Microorganisms cannot grow at a low pH, and chlorine may
interfere with metabolic activity, says Demirci. Combining these
produces a synergistic effect that kills microorganisms in a short time,
he says. The alkaline water, meanwhile, injures the microorganisms and
also works well as a cleaning solution for food-processing equipment.
last 20 to 30 years, advancements have been made in the small-scale
production of EO water so that it now can be generated on site. But
the challenge of this technique is in making sure the solution comes
into contact with the entire surface area of the food, especially the
tiny crevices where microorganisms hide. It is a matter of experimenting
with the parameters of the processsuch as contact time, temperature,
and even voltage and amperage applied to the machine to get better quality
EO waterto make sure it is effective, says Demirci.
many dairy farms go through a multi-step cleaning process on their milking
systems that involves the storage and transportation of concentrated
alkaline and acidic chemicals. But with a machine that generates EO
water, farmers would be able to make the two solutions on site when
needed. If we prove that this works, farmers would only need to
buy table salt, water, and electricity, says Demirci. At the research
and development level, EO water is proving to be highly effective, he
says. It removes almost all of the milk solids from the pipes and it
kills all of the microorganisms if given the proper treatment time and
temperature. EO water may eventually save dairy farmers both money and
Hung, a professor of food engineering at the University of Georgia,
is also working on various applications of EO water. We think
this technology has a lot of potential for the food processing industry
and also for the consumer at home to wash fresh fruits and vegetables
and to wash the cutting board, says Hung. He stresses the importance
of developing a smart machineone that attaches to kitchen sinks
and adapts to various needs. For instance, the water for washing a cutting
board might have different properties than the water used for washing
produce. We want to achieve the maximum effectiveness without
damaging the product or surface contact. You don't want residue
on food. But when you're washing a counter top, you might want
that water to have a residual effect, says Hung, who is also working
on enhancing the properties of EO water so that it will be less corrosive
when used on food processing equipment. In Japan, a washing machine
was recently introduced that uses EO water instead of detergent.
is also exploring an emerging technologyozonationthat destroys
microorganisms but leaves no residue behind. Ozonation is a process,
not an additive, says Demirci. After the treatment, the
ozone is converted back into oxygen. The challenge, once again,
has to do with contacting the entire food surface. Demirci is experimenting
with slight hydrostatic pressures and food-grade surfactants that break
the surface tension of the water, allowing the ozone to make contact.
We haven't reached the point where we can kill all of the
pathogens, says Dermirci. We can kill 99.9 percent of E.
coli 0157:H7 on alfalfa seeds, but unless it's at least 99.999
percent, we don't call it a successful process.
engineers are applying technologies to kill food-borne pathogens, they
also are adjusting the parameters of the very equipment needed to study
those pathogens. When scientists at the USDA Eastern Regional Research
Center in Wyndmoor, Penn., wanted to use a pilot plant setting to study
the effectiveness of controlling food-borne pathogens in commercial
fruit-processing equipment, they called on Paul Walker, a professor
of agricultural and biological engineering at Penn State. It's
hard to study pathogens in a commercial setting, says Walker.
The splashes, spills, and mists of the processing equipment would
very quickly spread the contaminants all over the place. The first time
that happens is the last time I want to enter that facility.
is developing a large containment chamber that both holds and decontaminates
commercial-style fruit processing equipment. That way, researchers can
determine the best strategies for controlling pathogens on a pilot plant
scale, including the speed and firmness of the brushes, the length of
the washing cycle, the water temperature, and the types of anti-microbial
agents to be used. During processing, the chamber is held under negative
pressure so no bacteria can escape. Once the processing cycles are complete,
the chamber is filled with steam to decontaminate the entire system.
to the Centers for Disease Control, food-borne illnesses can also be
caused by manmade chemicals. North Carolina-based Triangle Laboratories,
Inc. is marketing a new screen that reduces the cost and turnaround
time for detecting contaminants such as dioxins in food. RapidScreen
can be read by a layperson, guarantees no false positives, and takes
three days, instead of the traditional 25 days, says Chad Roper, director
of Business Development. RapidScreen's design evolved out of standard
EPA methodshigh resolution gas chromatography/mass spectrometry
and isotopic dilutionbut is tailored to the food industry. That's
what engineers do, says Roper. They take the proven technology
and apply it to a very specific circumstance. They take science and
modify the parameters to make it meet a real human need.
Alice Daniel is a freelance writer based in Fresno, Calif.
She can be reached at firstname.lastname@example.org.