More arrows in the quiver

by Bryan Brown |

September 30, 2004
Kevin T. Higgins, Senior Editor

There is no shortage of antimicrobial technologies for food and beverage processors. With safety concerns spreading, there is a need for even more.

Heavy-duty PVC curtains fabricated with an antimicrobial compound offer some assurance in heavy washdown environments when a work area must be cleaned and sanitized while production continues in an adjoining area. However, some food safety experts are questioning the wisdom of wet cleaning particularly with high-pressure sprays that can atomize and carry bacteria to other parts of the plant. Source: Goff’s Enterprises.

Bad news can be good news for food technology. Multiple recalls of ready-to-eat meats because of possible Listeria monocytogenes contamination illustrates the point: those events led to last year's Food Safety & Inspection Service risk-assessment system for meat plants, and that triggered a mad scramble for antimicrobial interventions that can help achieve a more favorable risk rating.

Fortunately, processors don't have to search very hard. The antimicrobial tool kit is brimming with interventions that go well beyond standard sanitation practices. They include natural solutions that are generally regarded as safe (GRAS) or are considered environmental aids under the purview of the Environmental Protection Agency. A primary example of the latter is silver-ion coatings and additives, such as AlphaSan from Milliken Chemical, HabaGuard from Habasit and Microban.

Pressure from regulators and customers may have piqued interest in antimicrobials and the clinical studies supporting their efficacy, but plant managers expect more than a microbiological solution from vendors. They want engineered delivery systems, as suppliers have come to realize. "Systems like ozonated water require service support and ongoing modifications," points out Jim Marten, vice president of Crown Solutions, Vandalia, OH. "It's not a plug-and-play scenario."

Delivering a turnkey solution can be a challenge. Two years ago, Lodi, WI.-based Alkar-Rapid Pak devised a steam pasteurization component for a hot-dog packaging machine. The unit blasts links with 260

Vacuum chambers with capacities of 2,000 to 9,000 liters handle dry foods in a batch process involving dry-steam sterilization. The technology developer claims up to 7 log reductions in microbes are achieved. Source: SteamLab.Systems GmbH.

Meat processors aren't the only food companies coping with the consequences of bad news. The second Salmonella recall involving almonds in recent years has put the entire tree-nut segment on edge. Traditional interventions such as ethylene oxide fumigation are being phased out and the likelihood of stricter limits on mycotoxins in nuts is adding urgency to processors' search for alternatives.

Aflatoxin in particular is a major concern in the European Union (EU), where tolerances are five times stricter for raw nuts than in the United States. Only 5 percent of US almonds are untreated, but that amounts to 15 million pounds, says Richard Waycott, president of the Almond Board of California (ABC). Those products likely will go the way of unpasteurized milk: the ABC has adopted an action plan that includes "eventual pasteurization of all raw product" with voluntary implementation for now, Waycott says.

In-shell pistachios from Iran have been a target of aflatoxin concerns. The EU rejected 200 containers of Iranian pistachios in 2002. Last year, the number rose to 508, more than a quarter of total shipments. A ban on untreated pistachios is under consideration, according to Gerard Markerink, sales representative for SteamLab.Systems GmbH, Hamburg, Germany.

In June, Spanish authorities issued an alert regarding aflatoxin in shelled almonds from the US. The same day, Swedish authorities flagged two shipments of soybean meal pellets because of Salmonella contamination. The alerts occurred just one month after five Salmonella poisonings linked to raw almonds from Paramount Farms were sold in Costco and Trader Joe's stores. Scores of Salmonella poisonings involving almonds also occurred in 2001 in two Canadian cities.

When the first incident occurred, "they thought it was a fluke," recalls Bob Kline, research director of the California Pistachio Commission in Fresno, CA. "Now they're scrutinizing the situation more closely. Can you have two anomalies back to back?"

Ethylene oxide is a potent antimicrobial agent that can eradicate virtually all bacteria, viruses, spores and fungi, the source of aflatoxin. However, ethylene oxide is banned in Europe and approaching that status in the US. Dry heat and fumigation with methyl bromide are other options, but current treatments are geared more toward insect infestation than antimicrobial action. The ABC wants producers to achieve 5 log reductions in microbial loads and, "as you can imagine, a number of purveyors have come knocking on our door to demonstrate the efficacy of their processes," Waycott says. Among them is SteamLab, which will install its dry-steam technology at an organic foods firm in Iowa next year, Markerink claims. Up to 42 tons of product a day can be processed in SteamLab's systems.

The process combines dry steam with a deep vacuum of 60 millebars to evacuate all air and allow steam as cool as 160

Trays filled with nuts are conveyed to a dry-steam treatment chamber. Both manual and automated filling options are available. Source: SteamLab.Systems GmbH.

Pressure to improve

Meat and poultry processors sit squarely on the antimicrobial hot seat, with both regulators and customers pressuring them to improve their risk ratings. Major customers such as Wal-Mart, Safeway and Sysco are insisting that suppliers attain Alternative Level one or two as a condition of doing business, according to Mark DiMaggio, business manager of food safety markets for BOC Gas. One retailer has set November 30 as a deadline for achieving those ratings, and suppliers who fail will be dropped. DiMaggio declined to identify the customer.

Ozone and ultraviolet light are two pathogen reduction weapons BOC is validating for meat processors. "Ozone is in its infancy," DiMaggio notes. "In protein foods, only about one percent of the industry has incorporated ozone so far, but I see that figure increasing exponentially." Seafood and produce applications also are expected to experience strong growth.

Silver Star Meats Inc. in Kennedy Township, PA, began using ozonated water for both equipment washdown and direct contact with sausages and hot dogs early this year. Backed by research data from the University of Wisconsin, ozone helped Silver Star attain Alternative two status. With Alternative three, weekly testing and inspection must be conducted. One day's production is placed on hold until test results are received, and that meant a lot of product in inventory, points out Dominick Bovalina, chairman and CEO of Silver Star Meats. The lower risk level requires quarterly testing and much less tied-up inventory.

While the generator installation is straightforward, ozone users need to be cognizant of venting and other issues posing a danger to human health. Crown Solutions was retained to integrate a stainless-steel ozone generator from Del Ozone into the Silver Star plant. Air filters were modified at the plant to ensure ozone gas did not exceed acceptable levels, Crown's Marten says, and returning water was routed through the bottom of the storage tank to prevent surface disturbances that might liberate gas.

The generator creates ozone gas that is injected into a 250-gallon polyethylene tank. Ozone at concentrations of 2 ppm is then pumped in pressurized lines to various points in the plant, such as drops for equipment washdowns, surface sanitation of conveyor belts and a spray chamber where product is treated in a post-lethality step. "Even at higher concentrations, we felt it had no residual taste impact," Bovalina says. In the University of Wisconsin study, kill rates averaging 1.5 logs were delivered at concentrations of 0.55 ppm.

Several hundred feet of PVC piping carry water throughout the plant. Because of the rapid dissipation of ozone, "you don't want the retention time in those lines to exceed five minutes," explains Marten. Ozone for surface sanitation is becoming popular in cheese facilities, he adds. The operator of a northeastern Ohio cheese plant eliminated chemical sanitizers in favor of ozonated water for surface sanitation.

CME Corp. fabricated these portable walls made by Arcoplast with a silver-ion antimicrobial coating. The walls are used in a food pilot plant at Ohio State University in Columbus. Source: CME Corp.

Bovalina believes the immediate lethality of ozone is most effective when combined with the slow, sustained microbial destruction from chemicals such as quaternary ammonia. Another way of achieving sustained kill is with antimicrobial coatings on steel and as an additive to polymers such as plastic conveyor belts. Silver ions are slowly released to kill bacteria, mold, mildew and fungi on a surface. But processors report mixed results: Cooper Farms tried a silver-ion coating on some contact surfaces in its Van Wert, OH, turkey processing plant but elected not to standardize it because swab tests were not significantly better. Rudolph Foods, on the other hand, is using panels treated with AlphaSan from Milliken Chemical in clean rooms of its pork-rind snack plant. Besides the antimicrobial property, the panels provide a highly cleanable surface.

Pilgrims Pride conducted its own lab tests on belting treated with Habasit's antimicrobial compound. The poultry processor has begun installing treated belts in its 26 chicken processing plants, according to Shane Calhoun, director of lab operations.

Like other suppliers of antimicrobial tools, Habasit is underwriting research studies on the efficacy of its products. Silver-ion systems are under the jurisdiction of the US EPA, and no positive benefits in combating food contamination can be made. On the other hand, studies by the University of Arkansas and North Carolina State University demonstrate the compound is useful in keeping pathogens in check and preventing the formation of biofilms. "We position the belting as an insurance policy," explains Bill Hornsby, Habasit's marketing director. The antimicrobial agent adds 30 percent to the cost of plastic belts.

The price premium for ceiling and wall panels impregnated with AlphaSan is even steeper. Craig Ralston, project developer at CME Corp. in Fort Wayne, IN, puts the cost at $18 or more per square foot, significantly higher than the fiberglass reinforced plastic it often replaces. But panels can be extruded in 8-ft. widths and up to 50-ft. lengths, minimizing the number of wall joints that can harbor bacteria. CME used the material to fabricate portable walls for product testing at Ohio State University's Food Industry Center.

Ticking off the names of some of the industry's biggest processors, Ghislain Beauregard, president of Arcoplast Inc., St. Peters, MO, says leading food companies are specifying panels in which an antimicrobial compound is part of the gel coating. Most processors are still kicking the tires, though, waiting for solid evidence of the durability and effectiveness of the treatment. A definitive answer should come from a study just underway at the University of California-San Francisco. Unfortunately, results won't be available until 2014.

"Yes, companies are scrambling for every tool they can get to increase plant safety," says Beauregard. "But they make sound judgments based on experience, and antimicrobials still don't have that experience."

Antibacterial agents such as lactates and trisodium phosphate, on the other hand, are established bactericides that can help elevate a plant to Alternative one status. That's the goal at Alkar-Rapid Pak, where a "pathogen lab" was created to validate its flash pasteurization process in tandem with antimicrobial treatment. Field testing of the machines is expected to begin in December.

"We've been getting the 3 to 4 log kills we expected," reports Bob Hansen, Alkar-Rapid Pak's vice president of R&D. The machines' design has been improved and simplified in the last two years. Stainless steel flash-pasteurization heads replaced aluminum heads, which eroded under extreme heat and pressure. Steam is indexed into eight pockets and sprayed onto the product. While the first generation machines required three valves per pocket, redesigned machines have four valves to simplify maintenance. The system is engineered to package up to 8,000 pounds of product an hour, Hansen says.

As with other antimicrobial tools, validation is an issue that adds time and expense to the system's deployment. Given the seriousness of system failure, it's a wait processors are willing to endure as they evaluate new technologies on the microbial front of the food safety war.