Food Safety / Technology / Cleaning, Sanitation, Hygiene

Technology Offers Gentler Processes For Pasteurization And Sterilization

Technology developers provide means to deliver minimally processed products without compromising food safety.

By Kevin T. Higgins, Managing Editor

Once an animal is slaughtered or produce is harvested, microbes go to work and deterioration commences. Louis Pasteur figured out this dynamic 155 years ago, setting in motion development of the pasteurization and sterilization technologies used today.

Pasteurization garners the most interest. The reason, as bank robber Willie Sutton understood, is because that’s where the money is: If two identical products are displayed in a grocery store, the refrigerated one will sell for a premium over the shelf-stable version. Microfiltration and high-pressure processing (HPP) expand the pasteurization tool kit, but there is no shortage of innovation in sterilization technology, too.

The 21st Century seemingly left retort in the rearview mirror, relegating this shelf-stabilization method to the ashbin of history. Overcooked and over-processed are common criticisms of retort. Canners have tried to rehabilitate retorted food’s reputation by lowering levels of salt and other preservatives, but long come-up and cool-down times in conventional retorts inevitably result in destruction of vitamins and other nutrients.

Agitation can shorten process time, and engineers have devised various approaches, such as rotating food containers on their axes. One of the earliest ideas envisioned agitating the entire retort vessels and was patented by Frank Gerber, founder of the baby food company.

A more realistic approach is rapid back-and-forth motion of the basket that holds the food containers. In 1993, process engineer Richard Walden began working on such a system, eventually winning multiple patents and bringing the technology to market through partnerships with retort manufacturers in Europe and North America.

Walden christened his system Shaka and partnered with Allpax Products Inc. to build a U.S. production-scale unit. The machine generates about 2 Gs of force as it completes 150-170 back-and-forth strokes of 6 inches every minute. Only one basket can be processed at a time, though Waldon calculated throughput could match an eight-basket static retort, depending on product viscosity, thanks to shorter processing times.

Shrinking batch time translates to energy savings, though the greater benefit is improved product quality. The concept drew interest from a number of major food companies and copackers, but a licensing fee tied to the number of containers processed prevented all but a handful from ordering a Shaka retort from Covington, La.-based Allpax (www.allpax.com). “It really turned off processors early on,” says Greg Jacob, vice president and general manager.

However, the process patent expired in October 2015, “and there’s new interest from people who want to get involved with the technology,” according to Jacob. A partnership with the Louisiana State University School of Nutrition and Food Sciences, where a Shaka R&D unit has been installed, promises to expand the scope of applications and formulations.

Louisianans are particular about their crawfish and shrimp, but retorting seafood usually results in rubbery food. Not so with Shaka. “The process time is so much shorter that shrimp has a good, fresh taste,” says Jacob. Shelf-stable guacamole doesn’t exist, but he thinks Shaka could produce such a product. And agitation is so vigorous, it might be possible to put packages of chickpeas or sweet potatoes into a machine and have a container of hummus or sweet potato puree emerge.

Beverages and other low-viscosity products are poor candidates, given their already short retort cycles, and pouches and other containers can pose process challenges (rectangular cans, on the other hand, are ideal). But as long as there is some liquid and head space to promote agitation, the system offers distinct advantages. “With the market evolving and the focus on fresh and better nutritional value, we’re in an interesting position with Shaka,” Jacob says.

Nutrient retention

Gentler processing also is the proposition with Spirajoule, a technology that has gained a foothold in food. Three North American companies are applying it to sterilize seeds, grains and other foodstuffs. Engineers at Safe Sterilization USA (www.safesteriliationUSA.com) modified Spirajoule for use with powders, as well.

Spirajoule relies on an electrically heated screw conveyor to thermally treat powders and particles as they move through the processing zone, inactivating yeast and mold cells. Dry steam usually is injected into the zone to further lower total plate counts, unless the product is hydroscopic and prone to lumping from the steam.

“When the steam flashes on the particles, it inactivates all the microbes,” explains Mayur Desai, an engineer and owner of Safe Sterilization as well as Bioactive Resources LLC, a supplier of nutraceutical ingredients. The companies are based in South Plainfield, N.J., with a recently opened tolling operation in Reno, Nev., expanding its ability to serve the organic ingredients market.

Microwave is another new-to-the-market means of sterilization. Like Spirajoule, advocates must first educate processors about the technology. That takes time, as managers at 915 Labs Inc. (www.915labs.com) can attest.

Denver-based 915 (a reference to the MHz frequency at which the single-mode magnetron operates) hopes to commission the first industrial-scale line for sterilizing low-acid products later this year. Known as MATS (microwave assisted thermal sterilization), the technology was developed at Washington State University and patented in 2006. Pilot units were delivered to military ration suppliers Ameriqual and Wornick in 2012, but no contracts with a North American processor have been announced.

MATS is designed for whole foods. Liquid and pumpable products are targeted by Aseptia Inc. (aseptia.com), Raleigh, N.C. An early version of Aseptia’s AseptiWave system has successfully produced aseptic sweet potato puree for Yamco LLC since 2008. More recently, four lines were installed at Wright Foods, a former Aseptia subsidiary that was sold to Ameriqual last year. When orders for additional AseptiWave systems are placed, they will be engineered by SinnovaTek, another Aseptia affiliate.

“We’re in discussions with a number of folks, but as far as having real scalps on the wall, we have work to do,” confides Mac McAulay, senior vice president and CFO. Besides product quality improvement, the firm is quantifying lower operational costs from energy and ingredient inputs. For example, researchers have demonstrated a 20 percent reduction in flavor ingredients in soup broth because cook-off from thermal treatment is avoided.

HPP’s pasteurization pivot

Sterilization with high pressure also is an option, and much of the primary research on HPP focused on shelf-stable foods, particularly those that fit with the Dept. of Defense’s Meals Ready to Eat program.

According to Kevin Myer, senior vice president of research & development at Hormel Foods Corp., the Austin, Minn.-based company continues to evaluate HPP as a sterilization step for shelf-stable products. Sterilization requires process temperatures in the 70°-90° C/158°-194° F range and pressure of about 120,000 psi, though, higher than the presses currently used can deliver.

“We didn’t have much success with sterilization in house,” says Myer, who has conducted research on HPP since 2001. But the company continues to evaluate possible process changes, such as the addition of ingredients that would help denature spore-forming bacteria and achieve sterilization at lower pressures.

In the meantime, Hormel is content to apply HPP pasteurization to high-margin products such as Natural Choice sliced meats. HPP also is gaining traction with start-ups like Zupa Noma, a line of chilled soups with “superfood” ingredients from Sonoma Brands, a California investment and early-stage development firm founded by Jon Sebastiani (drinkzupa.com). Sebastiani’s previous venture was Krave, a jerky brand that was sold to Hershey Co. for $218.7 million in 2015.

Launched in late summer, Zupa Noma has some retail distribution in California and New York metro, but e-commerce is the real focus. Six 12-oz. bottles sell for $84.
Building consumer awareness and the e-commerce channel is management’s primary focus. Contract manufacturers and tollers handle production and HPP pasteurization. “We are able to achieve a five-month shelf life for our superfood soups,” Sebastiani says. “We’ve found HPP to be a good fit for Zupa Noma. Consumers continue to tell us that they value the high quality of our ingredients and production methods.”

Pure Spoon (purespoon.com) has a longer track record with HPP, and processing was moved in house a year ago, four years after the firm’s start-up. The technology plays a big role in Austin, Texas-based Pure Spoon’s unique selling proposition: baby food as good as homemade.

“There is such a gap between the over-processed and gross baby food in stores and what you can make at home,” founder and CEO Alyson Eberle maintains. “We opened the doors for a new category, and we continue to work on explaining what high pressure processing or cold pasteurization is and why it makes a difference in the quality of the food.” Both Eberle and Sebastiani support the effort to brand HPP as cold pressure pasteurization.

Avure Technologies Inc. (www.avure-hpp-foods.com) is playing a lead role in that branding. “Cold pressure verified means that the proper protocols and procedures were used in the process,” explains Jeff Williams, CEO of the Middletown, Ohio, fabricator of HPP presses. “While you would hope no one would operate without a HACCP plan in place and a proper validation study, this is an effort to assure the public that no short cuts were taken.”

The technology is industrially hardened and mainstream, he adds. Continued growth depends on public awareness and confidence in the process.

Microscopic segregation

Strictly speaking, HPP does impart some heat: the temperature of food and beverages increases several degrees under 85,000 psi of pressure. For true nonthermal pasteurization, micro filtration may be the most benign treatment.

“There’s a humungous difference between 5- and 7-log reduction with filtration,” observes Colter Marcks, lead development engineer-process filtration at Donaldson Co. Inc. (www.donaldson.com) in Bloomington, Minn. Removal of 2 million cells per square centimeter of media is the standard for 5 logs; it’s 10 million cells per square centimeter for 7 logs, which is the requirement for pharmaceutical applications.

Unlike HPP, spores and other vegetative cells are removed with membrane filtration, though the technology is inappropriate for turbid fluids like orange juice, which would prematurely clog the media. Coconut water and apple juice, on the other hand, are candidates for micro-filtration.

Theoretically, milk could be pasteurized, though thermal treatment is required by the Pasteurized Milk Ordinance. Extended shelf life and a richer mouthfeel would be the only benefits from using filtration and heat in combination.

But interest in close-to-raw products and higher-quality beverages is creating opportunities for microfiltration. “Beer people are quite the experimenters,” Marcks says by way of example. “For a few thousand dollars, micro breweries can produce a sterile product that doesn’t require post-filling pasteurization.”

Winemakers are another growth category. “A 0.45 micron membrane is a perfect way to remove all the yeast in wine,” he adds.

Maintaining filter integrity over extended periods is the focus of technical improvements. To that end, Donaldson engineers developed a rectangular support structure for the filter media. “Triangles are structurally much stronger than squares,” the conventional configuration, he says. Donaldson’s cage design helps minimize the incidental movement that creates tension and eventual damage to the media.

Food safety is non-negotiable, but product innovation is trending toward minimally processed and retained nutritional properties. Gentler pasteurization and sterilization technologies provide a way for food and beverage companies to deliver innovative products without compromising safety.