Fresh Today, Safe Next Week

April 4, 2003
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The same technologies that deliver pathogen-free foods are the ones that extend shelf life.



Public scrutiny has compelled the food industry to focus singular attention on food safety. The practical need for extended shelf life (ESL) is never far in the background, though, and the reality is that ESL technology invariably makes food safer.

The juice business is a case in point. Projects designed to deliver fresh-tasting products with longer code dates were abruptly shoved into the background when four juice recalls occurred in rapid succession in October 1996. Cryptosporidium in apple cider was an eye-opener; more shocking was E. coli 0157 in apple juice manufactured by Odwalla and blamed for a young girl's death. That led to the draconian warning label mandated two years later by FDA for unpasteurized fresh juice.

The labeling requirement gave rise to commercial development of ultraviolet (UV) light as an alternative to flash pasteurization for fresh juices. Not coincidentally, UV treatment also can significantly extend the shelf life of juice products. The same pattern is repeated in other food and beverage segments as the industry applies high pressure, carbon dioxide and other technologies to deliver safe, long-lasting food.

New technologies aren't always called for; better understanding of existing ESL technology can also be a priority. For example, ultrapasteurized dairy products are projected to dominate the fluid milk category as major grocers press demands for product with 35- and 40-day code dates delivered to warehouses instead of directly to stores. Yet dairies are operating without a clear blueprint of good manufacturing practices (GMPs) for these products, a shortcoming that is now being addressed by dairy producers, equipment manufacturers and regulators.

GMPs for dairy

When ESL dairy ermerged as a commercial product in the mid '90s, processors and their suppliers were confident of the integrity of ultrapasteurized ESL milk. That made February 1999's Listeria monocytogenes-linked recall of Land O'Lakes 2% ultrapasteurized milk so stunning. It's also why the National Center for Food Safety and Technology (NCFST) launched an ESL task force for fluid dairy products last summer. GMP recommendations will be available, and regulatory changes will be recommended, according to Charles Sizer, NCFST director.

The 1999 recall involved product produced by Kohler Mix Specialties, a subsidiary of Michael Foods Inc., and it underscored the heightened risk of ESL dairy compared to standard pasteurized milk. Because the process destroys spoilage organisms along with pathogens, any surviving spores or bacteria can grow without obvious signs of spoilage. Shelf lives of 30 to 45 days give those cultures added time to multiply, creating a scenario in which people unwittingly consume a lethal product.

"One of the prerequisites for HACCP is to have GMPs, and there basically isn't one for putting out ESL dairy at this point," observes Sizer. "It's mind-boggling that there hasn't been any documentation."

USDA regulations merely require a temperature of 280 degrees F for 2 seconds, defaulting to standard pasteurization procedures for everything else, and that can cause problems.

For example, diversion valves required in standard processing systems can lead to product contamination in ESL, and the task force will recommend a change in that requiremen. Likewise, daily cleaning of CIP aseptic tanks has the potential to do more harm than good. "Anytime you go through a cleaning cycle, you compromise sterility," points out Sizer. "In Europe, they're running these tanks for weeks without losing sterility." The task force is expected to recommend a few day's gap in ESL tank cleanings, a change that also would save processors about four hours of downtime for each day they can skip.

NCFST is cosponsoring a symposium on ESL foods May 17-18 in cooperation with the Institute of Food Technologists, and the task force's work will be discussed. Also on the program will be high hydrostatic pressure processing (HPP), a technology which Sizer believes has great potential for delivering safe, high-quality ESL foods, even without refrigeration (see related story).

Flow International Corp. is the only supplier of HPP units, and oysters and guacamole dip are the only U.S. retail products currently produced through HPP -- in guacamole's case, at 87,000 psi. But processors are taking a hard look at high pressure, and more products are likely to appear in supermarkets this year.

One candidate is Milwaukee's Emmpak Foods. The presses are pricey -- more than $1 million per unit -- and the equipment's large footprint poses a challenge, but HPP's performance in microbial challenge tests has been superlative, Emmpak officials report.

"The technology is great," says Tom Rourke, vice president of R&D. "It would double the shelf life and in some cases triple it for pre-sliced, packaged meats."

Citing a study by Business Communications Corp., Flow managers say HPP will command the lion's share of the booming nonthermal processing market projected to reach $426 million in two years.

Meat processors are the strongest potential market for high pressure, Flow's Rick Marshall says, and juice companies are another promising segment. But HPP's cost puts it out of reach for small and mid-sized firms. Thermal pasteurization costs significantly less, but heat pasteurization isn't an option for juice makers serving health-conscious consumers. Those processors need a more benign procedure at an economical cost. The emergence of ultraviolet (UV) pasteurization just may fill the bill.

Low-cost UV pasteurization

Health-conscious consumers don't want nutritionally compromised products, and thermal treatment destroys the enzymes that are digestive aids and have been linked to cancer remissions and other positive health-care outcomes. But the absence of any pasteurization precludes achieving a 5-log reduction in E. coli, Listeria and Salmonella pathogens, and that means placing a warning label on those products.

Fortunately, UV light can achieve the required pathogen reduction, and in November the FDA amended the food additive regulations to acknowledge the effectiveness of one UV treatment. Salcor Inc. developed the technology in cooperation with California Day-Fresh Foods Inc., a Glendora, Calif., processor that began marketing four UV-treated vegetable juices in January. The process also will double and possibly triple the shelf life of California Day-Fresh's juices.

Otherwise, the company's juices have to carry a label reading, "Warning: This product has not been pasteurized and, therefore, may contain harmful bacteria that can cause serious illness in children, the elderly, and persons with weakened immune systems."

"The warning label on fresh vegetable juice has made a bigger impression on consumers than the warning label on cigarette packages," says Dominic Marlia, California Day-Fresh's quality assurance manager. "Our volume has dropped drastically because of that label."

ESL was the goal when California Day-Fresh began investigating UV treatment four years ago. That was before food safety became the only imperative. By applying a minimally intrusive process like UV, the company is able to deliver a product that satisfies both objectives.

The process will preclude marketing these juices as fresh, but that's a tradeoff the company is happy to make in return for dropping the warning label. Marlia anticipates a significant sales rebound, in part because of greater consumer acceptance but also because of the wider distribution possible thanks to longer shelf life. "This process has enabled us to extend our vegetable products' shelf life to 10 days, which will allow us to ship these items to the Pacific Northwest and states as far east as Colorado," he says.

FDA's endorsement of the Salcor process prompted a formal protest from engineer Phil Hartman, codeveloper of the CiderSure UV machine for roadside apple cider producers. Unlike Salcor's system, which relies on a turbulent flow to denature pathogens, CiderSure employs film that is 0.0003 inch thick. The machine is ill suited for juices with particles thicker than 150 microns, so juice can't contain any fiber. Hartman's objection is based on FDA's specification of a turbulence-based process, instead of pathogen-reduction performance.

About 65 CiderSure units have been validated for use by small cider producers, a segment of the juice business devastated by the warning-label requirement. In Massachusetts, only four roadside cider makers remain, compared to 40 before 1998. The story is the same in other apple-producing states, and the CiderSure unit, priced around $15,000, has been a lifeline for the survivors.

The Salcor unit costs twice that, but it is considerably more versatile and is suitable for higher viscosity juices, including the carrot blends California Day-Fresh will market under the Naked Juice brand. And the processing cost is modest compared to other options, notes James Cruver, president and CEO of the Fallbrook, Calif., firm. He pegs UV's cost at 0.2 cents per gallon compared to a nickel for heat pasteurization and three times that for nonthermal processes such as carbon dioxide and high pressure.

California Day-Fresh's Marlia estimates liquids of up to 50 centipoise could be processed with the system. The unit contains 300 feet of Teflon-like fluropolymer tubing that is impervious to acids and provides a nonstick surface. The tubing is rated at 140 psi, and using three units in succession would boost pressure to 100 psi, but engineers preferred to err on the side of caution and used two machines, which produce 85 psi. A Waukesha Cherry-Burrell positive displacement pump links the units.

ESL through controlled ripening

Boatloads instead of plane-loads of South American fruit are now bound for American grocery stores, thanks to a water-soluble polymer coating that emulates controlled atmosphere packaging. The coating controls the penetration of oxygen into harvested produce and the transmission of ethylene gas and carbon dioxide out. On Christmas Eve, the FDA gave its food-contact approval to the coating. Two days later, the inventors' were granted a copyright.

Marketed as FreshSeal, the film has gone from "an R&D curiosity" to a mainstream product in less than a year, notes Howard Kravitz, vice president of business development for CPG Technologies, the Syracuse, N.Y., licensee of the process. The first commercial application involved 500,000 cartons of mangoes. A quarter-million cartons of cantaloupes were the subject of a summer field trial, and Kravitz says an October test with Chilean avocados quickly ramped up to include two boatloads of the fruit.

The coating compound is made from material generally regarded as safe, but getting the FDA's imprimatur "sets people's minds at peace" and should greatly expand market acceptance, Kravitz predicts. CPG will feature the ESL breakthrough at March's United Fresh Fruit & Vegetable Show in Tampa, Fla.

Scientists at Planet Polymer Technologies Inc., San Diego, developed the coating. Planet Polymer has developed biodegradable films for 3M and Kimberly Clark. FreshSeal represents its first foray into foods. The film is designed for produce with skins not typically consumed by humans, and Planet Polymer is pursuing FDA approval for an edible version for tomatoes and other produce consumed whole.

A typical solution is 5 percent polyvinyl alcohol and 0.5 percent starch, with trace amounts of surfactant for uniform coating and glycerin to aid the movement of gas molecules. By varying concentrations, users can accelerate or delay the ripening process. An antimicrobial agent can be added, though that affects gas-barrier properties. The solution typically is sprayed onto produce and dries to a clear, colorless film.

Field tests involving various fruits showed FreshSeal added one to four weeks shelf life at ambient temperatures. In a test involving mangoes shipped from Mexico to the U.S., uncoated fruit arrived in a deteriorated state and had to be sold as seconds. A second group had a two-week shelf life and, more importantly, fetched a premium double the normal price. "The third group lasted five weeks, and the shipper sold them at a three-times premium," says Robert Petcavich, Planet Polymer's chief technical officer.

Reduced spoilage is one benefit, but Kravitz believes the greater value is in lower shipping costs. The freight costs for produce sent by sea are a tenth of air shipments, he says, and FreshSeal is being priced to reflect that value. CPG plans to manage the spraying operations at packing houses in cooperation with clients, he adds.

Cold chain management

High tech grabs headlines, but better control of old technology can be more important in extending life. Temperature abuses can occur in distribution or at the store level, and pinpointing problem spots can be difficult, if not impossible.

Packaging technology helped usher in the age of fresh-cut vegetables, marked by success stories like ready-to-eat salads. Breathable films allow those vegetables to respire and delay spoilage. But as sophisticated as that ESL technology is, manufacturers say that maintaining proper refrigeration is even more important.

As a rule of thumb, one day's shelf life is lost for every two degrees above the optimal handling temperature for a food, according to consultant Nick Pacitti of Nvision Logistics, Hudson, Ohio. Abused products may not pose a health risk, but severely compromised quality can torpedo repeat sales.

"Companies are engineering products that can tolerate temperature abuse, but consumers will eat them and say, 'This is disgusting,'" warns Pacitti. Time/temperature tags in transit cars and grocers' coolers generate reams of data, but turning data into an actionable plan is almost impossible, he maintains.

Pacitti works with Sensitech Inc., a maker of temperature and humidity monitoring equipment that recently acquired Ryan Instruments. As a former Nestle employee involved in the now-defunct FreshNes line, Pacitti used Ryan monitoring equipment. "It would take two hours to manually calculate a couple of days worth of temperature readings," he laments.

Equipment now can be married to database software that automates the task. "Today's databases are light years ahead of where they were just five or six years ago," Pacitti says. "Now the tools exist to address out-of-spec products."

Whether it's technology as fundamental as refrigeration or avante garde as controlled atmosphere coatings, manufac- turers are taking advantage of tools that not only render food safe but also extend shelf life.

Sidebar:
DUST takes aim at shelf-stable ESL technology

When the U.S. Army talks about extending food's shelf life, it's understood it's to be done without benefit of refrigeration. That means processing must achieve sterility, not simply pasteurization. If two food research projects bringing the military and food companies together bear fruit, commercial ESL will one day mean stable without refrigeration.

The projects involve the study of pulsed electric field technology at Ohio State University and high pressure processing at the National Center for Food Safety and Technology (NCFST) in suburban Chicago. Both are under the auspices of Dual Use Science and Technology (DUST), a series of programs aimed at commercializing technology that's been developed for the Department of Defense, NASA and other federal agencies.

The army is providing $2.3 million for the NCFST project, with Kraft Foods, ConAgra, Procter & Gamble and Flow International chipping in additional support. Preliminary work began last year, but the three-year program shifts into high gear this summer when NCFST takes delivery of a 35-liter high-pressure unit capable of processing a wide variety of foods in a commercially-scalable machine.

"It's a very versatile unit that will support the DUST program's goal of commercializing shelf-stable low-acid foods," according to NCFST's Charles Sizer, who views the technology as a "pressure-accelerated thermal process" capable of much more consistent, higher quality results than thermal processes "with a minimum of chemistry going on." High pressure raises food's temperature 5 degrees F for each 15,000 pounds of pressure; experiments will apply 90,000 psi.

"We will process foods at 80 to 90 degrees C, which gives synergistic ability to kill spores and create sterility," adds Flow researcher Edmund Ting, who is serving as project director. Products to be tested include mashed potatoes, vegetables, beef stew and cheese products.

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