Out with the Old ...

March 22, 2003
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... and in with new nonthermal processing technologies for the food and beverage industry.



Preservation, not preparation, is the basic reason food processors precook the products they sell, and nothing preserves and protects food from Clostridium botulinum like a high, hot cooking flame.

Until now. A host of nonthermal processes are coming on stream to delay spoilage or at least reduce the likelihood that people will get sick from fresh foods that were processed hundreds, even thousands of miles away. Some of these technologies -- notably high hydrostatic pressure (HHP) and irradiation -- have emerged as full-blown commercial processes, while others like ultraviolet and carbon-dioxide treatments are at various developmental stages. Still others already are widely used in other fields: more than 3,000 bottled water suppliers use ozone to purify their products, and the city of Boston is building a $600 million ozone system, yet food companies are just beginning to use ozone in direct food contact. These technologies may never replace retort processing, but they extend shelf life and result in more flavorful foods, two objectives high on processors' priority lists.

High pressure is scoring impressive gains. More than 70 units have been installed or are on order, according to Flow International, the major supplier of HHP systems. Those applications include the packaged meats category, where Hormel and Emmpak Foods (see related story, page tk) are applying the technology; fresh juices and oysters. Although a small segment of the industry, oystermen were among the earliest converts to high pressure, and the number of users is increasing.

Warmer water temperatures encourage growth of the microorganism Vibrio, which takes root in oysters and causes cholera in humans who eat them. Gulf Coast oystermen in particular are plagued by Vibrio-tainted oysters, resulting in widespread recalls and scores of gastroenteritis outbreaks. Motivatit Seafoods in Houma, La., added twin 45-litre high-pressure units two years ago. Nisbett Oyster Co. in Willapa Bay, Wash., recently followed suit, and Joey's Oysters Inc. in Amite, La., is awaiting delivery on a 215-litre unit.

Rising water temperature in the Northwest resulted in a Vibrio-related recall a couple of years ago. But product pasteurization wasn't David H. Nisbet's motive for purchasing twin 45-litre pressure vessels; instead, it's the increased yields and partial shucking from HHP that prompted him to purchase the unit.

"You're dependent on a labor pool that's drying up," says Nisbet, who markets his oysters under the Goose Point brand in major supermarkets. "We really don't have Vibrio problem here. This is more of an aid for shucking." Besides reducing labor costs, HHP will allow his company to do some value-added processing of shellfish. He is processing oysters at 35,000 psi for 90 seconds.

Frank Boudreaux of Joey's Oysters seconds Nisbet's point about the labor issue. "We used to have 300 to 400 shuckers in this little town," says Boudreaux, the firm's vice president. "Now we're down to 50, and 80 percent of them are over 40. Nobody wants to grow up to be a shucker anymore.

"Pressure doesn't shuck the oyster, put it releases the abductor muscle and pops the shell open about an eighth of an inch. I've been doing this for 30 years, and this results in the best-cut oyster I've ever seen."

High pressure doesn't come cheap: Joey's will pay seven figures for its unit, and Boudreaux worries that low-priced knockoffs will become available and put his company at a competitive disadvantage. And these are not large companies: Nisbet Oyster has sales of less than $3 million annually. But the technology overcomes a growing concern of public health officials and allows these firms to offer a saltier, more savory product than what currently exists, HHP proponents say.

Virtually all the new processing technologies coming to market are evaluated by scientists at the National Center for Food Safety and Technology in suburban Chicago. "With some exceptions, these technologies have potential for increasing the safety of food," NCFST Director Charles Sizer says, but the technology that most excites him his HHP. "There isn't a question in my mind that we can create shelf-stable products with high pressure. The problem is, we can't validate it."

While scientific measurement struggles to meet HHP's validation needs, Sizer says the rapid cool down that occurs after pressure is released means that better quality results. The same could be said about irradiation, a technology Sizer calls "one of our very important tools." With SureBeam Corp. and IBA adding processing capacity, he predicts irradiation will become common practice in the near future.

Frozen beef from Huisken Meats, Schwan's (which is supplied by Huisken) and Omaha Steaks have been the most visible irradiation stories from SureBeam, and the company is beginning to make inroads into foodservice with Minnesota suppliers Rochester Meat Co. and WW Johnson. In April, FDA approved IBA's petition to irradiate pet foods, a development that irradiation proponents believe could help break down consumer concerns about the process.

Rawhide chew toys are susceptible to salmonella contamination, and cases of the bacteria being transmitted to dog owners have been documented. Radiation sterilization of the treats and possibly dry pet foods will mean those products will carry the green radura symbol, and that should help make consumers more comfortable with the process, suggests Pat Adams, president of IBA's food safety division.

In July, IBA expects to commission a 70,000-sq.-ft. irradiation facility in Bridgeport, N.J., to process both food and medical supplies. The plant will feature the Rhodotron, a high-energy system that uses magnets to accelerate the strength of the beam, which then is split to perform X-ray processing on one side of the plant and electron-beam processing on the other. The rose-shaped system derives its name from rhoda, Greek for rose.

IBA also has received approval to irradiate food at its suburban Chicago facility. A Chicago plant is in SureBeam's future, too.

Green light for ozone

Even old technology can be new when placed in a fresh context, as is the case with ozone treatment in direct contact with food. The first use of ozone to treat drinking water occurred in 1906 in Nice, France. In 1982, FDA declared ozonization to be Generally Regarded as Safe (GRAS) in a Bottled Water Declaration. Buried deep within the 52-page declaration, however, was the stipulation that any application of ozone in contact with food would require a food additive petition (FAP).

Ozone experts now lambaste the stipulation as an oversight or worse, but the ruling was largely overlooked at the time because no food-contact applications existed. That has changed. Ozone's power as a superior oxidizing and disinfecting chemical for food is now clear. But a GRAS declaration by an expert panel in 1997 ran aground on the FAP proviso, setting the stage for regulatory wrangling and legal saber-rattling. Last August, a broadly written FAP from scientists representing the Electric Power Research Institute was filed with FDA. The petition essentially would clear the way for ozone treatment with meat, poultry, fruits, vegetables and most other types of foods. Final approval was anticipated in May.

The impact will be immediate. One ozone consultant reports that a major food company is poised to apply ozone in food contact at 70 plants as soon as FDA acts, while a small juice processor is among firms that quietly have added ozone treatment in advance of formal approval.

Nashville-based Strickland Produce Inc. has eyed ozone treatment for fresh-cut vegetables for five years, with serious study being conducted since 1998, according to Walter Strickland, CEO. An ozone sanitizing system was awaiting startup on one line in April, pending FDA approval, and Strickland says he'll add similar units throughout his plant as soon as practical.

"Chlorine is still a very effective method for sanitizing and the easiest to administer, but ozone in combination with chlorine is the best approach," he says. "You get an improved flavor from fruits and vegetables, and it is very beneficial in extending shelf life, though we don't intend to promote that benefit by extending code dates. There is a real benefit to eating vegetables close to harvest because of the nutritional aspects."

Strickland's ozone system also treats wash water, reducing the amount of waste generated by the plant. Poultry processors and others are applying ozone to waste-water treatment, particularly in areas of the country where water supplies are stressed.

Ozone is created with an electrical arc that splits the oxygen molecule, with the two resulting elements quickly binding with two other oxygen molecules for a short half life. The phenomenon occurs in nature during a lightning storm, and ozonization proponents claim the same fresh, sweet smell in the air after a storm occurs after a properly applied ozone treatment.

Strickland attests to the positive taste from the ozone process. "With some bottled water, there's a flat taste," he says. "I choose ozone-treated water because it almost has a sweet taste, like mountain water."

Whether consumers will notice any taste difference from ozone-treated foods is unclear, but some observers are betting their noses will notice a change. Processors of fresh-cut vegetables often spritz their products with residual chlorine at the time of packaging as a safeguard against post-packaging contamination, points out Chuck Sopher of the Agriculture and Food Technology Alliance. The smell is noticeable when the bags are opened. With ozone treatment, the amount of chlorine used should be well below perceptible levels.

Only a handful of suppliers are currently serving the food industry's ozone-generating needs. That will quickly change, and ozone experts worry about negative fallout from improper handling. Fifty foodservice workers were injured, some seriously, when improper ventilation in a washdown area caused overexposure to ozone vapors, and at least seven cases involving university researchers who breathed too much ozone have been documented. Proponents also worry ozone will get a black eye when processors apply concentrations with too little or too much ozone to food surfaces.

"Neophytes can cause real trouble with ozone," frets Louis D. Caracciolo, a special consultant to BOC Gases who holds numerous patents for ozone generation and food applications. "There's going to be a lot of hocus-pocus after FDA approves direct food contact, and new suppliers will be coming out of the woodwork."

Ozone's effectiveness in treating lettuce has prompted one major quick-serve restaurant to order its suppliers to commence ozone treatment once FDA gives the go-ahead. Unfortunately, the proper dosage and exposure levels for other foods are not well understood, and published research reports often contain contradictory findings.

"Many of the reports written by my fellow PhDs leave out critical details about what exactly was done, so it's impossible to say if ozone treatment is or is not effective for that particular food," points out Rip Rice, an Ashton, Md.-based consultant and cofounder of both the International Ozone Association and the International Ultraviolet Association. "We don't know yet how to use ozone in many applications."

Some scientists have dismissed ozone as ineffectual in killing pathogens on the surfaces of apples, citing research that indicated marginal E. coli log reductions after washing with ozonated water. Likewise, ozone oxidation can react with lipids in fowl carcasses and lead to rancidity.

But those outcomes are a consequence of misapplication, ozone experts say. Elevated ozone concentrations to achieve a 3 to 5 log pathogen reduction on poultry will oxidize the skin, Rice concedes. However, a 1- to 2-log reduction is attainable without the negative side effect.

Ozone in combination with ultrasound is another option. The ultrasound knocks the bugs off the carcass, and the ozone in the water bath ruptures their cell walls. The strategy can reduce microbial loads to acceptable levels, Caracciolo says.

"Researchers' training and orientation is pathogen log reduction, but for chicken processors it's a matter of percentage reduction throughout the plant," he says. "With ultrasound-based ozone technology, I can reduce campylobactor, for example, to 10 percent. I couldn't do that without ozone, but it isn't the ozone itself. And you've now positioned the product for the next antimicrobial treatment."

Unlike chlorine, which is a systemic poison, ozone also destroys cryptospodium and other parasites, and it doesn't leave a residue. It also eliminates the storage problems associated with peroxide, chlorine dioxide and other sanitizers and is two to three times more effective in reducing pathogen loads.

Focus on juice HACCP

With juice manufacturers scrambling to meet required pathogen kill rates of 5 logs without resorting to thermal treatment, benign processes such as ultraviolet and carbon dioxide are gaining a commercial foothold. Validation work is underway at NCFST for a laminar-flow UV unit from Aquionics Inc., which could gain FDA approval, just as a turbulent-flow system from Salcor Inc. did last fall.

Tatiana Koutchma heads NCFST's UV evaluation efforts. The joint FDA-Illinois Institute of Technology project has documented the effectiveness of germicidal UV wavelengths in disrupting pathogens' DNA, much like irradiation disrupts their ability to reproduce. Now the team is focusing on destruction of Vitamin C in the juice of oranges, carrots and apples and at the effects of absorption properties of various juices on UV kill rates.

Pulp and other particulates are the limiting factor with UV. They create a shadowing effect, shielding juice from the pasteurizing capability of the light.

Shadowing is not an issue with carbon dioxide, which is being combined with 5,000 psi of pressure in a carbon dioxide system designed by Praxair. A pilot project just ended with a California juice manufacturer, and Danbury, Conn.-based Praxair is offering the system on a no-money-down lease basis. Clients would pay 15 cents per gallon processed, according to marketing manager David Farmer.

Validation of the system's final design is being handled at NCFST, which is serving as process authority. "We're trying to understand the effect of high pressure and carbon dioxide in combination," explains Sizer. Carbon dioxide forms carbonic acid, which lowers pH and helps extend shelf life, he adds.

"This isn't going to replace extreme thermal processes that can give 60 days to 18 months shelf life," Farmer says, "but it can replace thermal processes such as flash pasteurization." Cloud stability is increased, giving fruit and vegetable juices an appearance somewhere between the separation of fresh juice and the uniform opacity of heat pasteurized juices.

The Praxair process was developed by Murat Balaban, a University of Florida food scientist who began work on the process in 1987. By comparison, HHP had its genesis a century ago, though it remained a novelty until a high-pressure containment vessel was developed.

Five log reductions are easily attainable for common pathogens, Balaban says, and the process is "fairly effective with spoilage organisms. It at least doubles shelf life compared to unpasteurized juices, and in all our taste tests, consumers could not tell the difference between juice treated with this process and fresh-squeezed juices." The process gives meats a cooked appearance and turns shrimp mushy, but for products requiring pasteurization, carbon dioxide and pressure in combination are effective, he says.

While nonthermal processes are coming into their own as a food preservation tool, they will only augment, not replace, the heat treatments used today. "A hundred years from now, we'll still be doing thermal processing, but we'll be doing it better," suggests NCFST's Sizer. "There's a lot of room for improvement."

The same could be said about many of the nonthermal processes. Much remains to be learned about the best applications for specific foods and beverages. As commercial rollouts accelerate, so will the industry's learning curve.

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