Sanitizing Solutions: Silver, ultraviolet light among new methods under investigation
Any produce processing plant needs to have a sound sanitization program in place, and this normally involves a mix of chemicals and water to sanitize the produce itself and the equipment it goes through.
Hank Lambert, CEO of Pure Bioscience, a Chicago-based company that develops and markets technology-based bioscience products that provide solutions to numerous global health challenges, said the company is starting to use Silver Dihydrogen Citrate as a sanitizer.
While the use of silver as a sanitizer is a bit unconventional, Lambert asserts that silver’s history makes it a savvy solution.
“Silver has been known for centuries for its antimicrobial properties, and Pure Bioscience originally patented our antimicrobial technology in the core molecules Silver Dihydrogen Citrate, which is silver ion suspended in citric acid, in 2001,” he said. “Since then we have developed 11 additional patents for methods of use and formulation, so we have been able to test and demonstrate the superior antimicrobial efficacy of silver as a disinfectant in multiple applications.”
While Pure Bioscience’s Hard Surface product line’s primary use has been in processing plants, it’s also being used as an antimicrobial cleansing agent for avoiding germs at all levels, including as a food contact service disinfectant.
“Today we are focused on applications in restaurant settings, foodservice settings and also food processors, including produce processors,” Lambert said.
In his opinion, it makes perfect sense for a produce processor to utilize as a sanitizer.
“In terms of breadth and speed of pathogen kill, versus disinfectants and sanitizers currently being used in the market today to disinfect equipment in the processing department, Pure has been able to demonstrate a broader breadth of pathogen kill in addition to faster kill times,” he said. “For example, it kills listeria, frequently present in wet processing facilities like produce processing, in two minutes, whereas competitive cleaners in the market today that are chlorine-based or ammonia-based take up to 10 minutes.”
Similar superior kill-times are in effect for other pathogens frequently found on produce items, like salmonella, E. coli and others, he said.
“Equally important is we are non-toxic,” Lambert said. “The EPA has four categories for toxicity and Pure Hard Surface is an EPA type 4, and most competitive sanitizers are either category 1 or 2, so it doesn’t need to carry warning labels or skull and crossbones; we’re non-irritant, tasteless, odorless, colorless and non-corrosive.”
Although the technology has been around for a while, it wasn’t until the summer of 2013 that Pure Bioscience made the strategic decision to bring products to the commercial market to address the growing concern of foodborne illness.
“We focus the company strictly on the food industry, and focused the product as a food safety solution beginning in September of 2013,” Lambert said. “When we started, there was almost no awareness in the food industry of either our brand or our technology, so we’ve had to build that up over time.”
Currently, the Hard Surface product is being used in 15-plus food processors to varying degrees and is testing in five national restaurant chains (including Subway). Produce processors are testing it as well, but to date there is no official data on the results.
Let There Be Light
The Center for Produce Safety recently funded a research report about the possibility of using UV light as a sanitizing agent, something that would be a great asset to produce processors.
Bob Whitaker, chief scientific officer for the Produce Marketing Association, said UV is a strong agent that can be used to sanitize the surfaces of things, and it’s currently used in labs with hard surfaces.
“At the end of the night, you can flip on a UV light and pull a screen down and it can be used to kill any bacteria on a surface,” he said. “The proposal put forward is an extension of that same concept.”
Any time produce gets wet, moisture attracts pathogens, so lots of work is done in processing plants to dry produce after sanitization. According to Whitaker, there are some fruits that are so sensitive that putting water on them would cause them to rot, because the moisture couldn’t be dried, so the need for another solution exists.
“Something like a peach would fit into that category, where water would not be a good thing to use,” he said. “What else could you use to eliminate any potential pathogens that might find themselves on that peach when it’s being grown or harvested? It’s been proposed that something like UV, which doesn’t require water, could accomplish sanitization without causing any physical harm.”
In the study being funded by the Center for Produce Safety, researcher Xuetong Fan of USDA and his research team are hoping to find the appropriate dose levels and exposure times of UV to become a viable solution.
Fan writes in the research report that the proposed project is designed to study the feasibility of applying ultraviolet light to tree-ripe fruits (apricots and/or peaches).
“Specifically, we plan to assess the efficacy of UV-C (germicidal UV light) in inactivating common enteric human foodborne bacterial pathogens and maintaining fruit quality during post-UV storage,” he said. “Furthermore, to ensure and validate uniform UV-C exposure of all fruit surfaces, a rotating conveyer and the use of UV film dosimetry will be evaluated. In addition, the technology will be tested in commercial trials with our industry cooperator. Successful demonstration and implementation of UV-C technology will enable the fruit industry to meet the requirements of the Food Safety (Modernization) Act, while improving microbial safety and increasing the consumption of healthful fresh fruits.”
Whitaker said researchers need to come up with ways for UV light to be used correctly so that the produce is not just being sanitized in certain areas.
“UV like all light comes in a straight line, so if you are trying to hit a circular target like a peach, it’s a challenge to do that,” Whitaker said. “You can have different light sources coming in at different angles, or you can rotate the peach so it gets the right dose and exposure time uniformly across the surface.”
The produce industry has utilized UV light before, both on equipment and on return water, and its history for eliminating bacteria has shown positive signs.
Ideas Are Flowing
The prospect of both silver and UV eventually helping produce processors is valid. According to Whitaker, there are lots of other innovative ideas floating around concerning sanitization.
“Some people are using gases. The one frequently tried has been ozone, the strongest of the oxidizing agents that is known, and it has a kind of green element to it, but it’s hard to use because it’s hard to get that in water or concentrations that are effective,” he said. “You can use it as a gas, but that’s a little harder to use because you don’t want it to off-gas or it can be detrimental to workers around it. Chlorine dioxide is another gas that is used, but not as strong.”
Other researchers have considered essential oils as sanitizers. Herbs and spices for the most part are used for elements of these essential oils, with product such as rosemary or sage being used.
“The problem with that is it can be quite expensive and there have been issues with trying to separate them out from things that might impart flavor or odor,” Whitaker said. “While they are great smells on their own, it’s not so good if you want to treat lettuce or something with it.”
And aside from UV light, other energy sanitizer considerations have included X-radiation in a dose vs. time issue.
“There’s a lot of fine tuning that needs to be done on a lot of these, but the ones that we seem to understand the best are the ones that are aqueous driven and lend themselves more to the high-volume, high bulk type of cleaning processes that you see with fruits and vegetables most often,” Whitaker said.
— By Keith Loria, contributing writer
