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Patented anti-microbial: A future silver lining in packaged food safety?

Patented anti-microbial: A future silver lining in packaged food safety?
SDC easily enters the microorganism like a “Trojan Horse” through membrane transport proteins and causes irreversible damage to the DNA and protein structure.

A patented disinfectant formulation that synergistically combines citric acid with the known bacteriostatic properties of ionic silver is potentially applicable for treating packaging.


Silver has been widely recognized and accepted for decades as an antimicrobial agent used for treating surfaces. To keep up with the times, Pure Bioscience, a company dedicated to food safety solutions, has created and patented technology, silver dihydrogen citrate, trademarked “SDC.” The company states that SDC is the first new-generation, patented antimicrobial to be registered with the U.S. Environmental Protection Agency in more than 30 years.

A committee of independent experts critically reviewed efficacy and toxicity data for SDC and the SDC-based Pure Hard Surface disinfectant and food contact surface sanitizer. It found no evidence that SDC demonstrates a hazard to the public when used as a contact biocide on food contact surfaces and food-use utensils and therefore concluded its use as Generally Recognized As Safe (GRAS). This sets the stage for additional GRAS projects to determine SDCs suitability as an indirect and direct food additive in food processing.

In its commercial form, the product Pure Hard Surface kills bacteria and viruses in as few as 30 seconds and provides 24-hour residual protection.

Patent filings for solid formulations of SDC that are in development cover these materials of potential interest to our packaging audience: Solid polymers, laminates and paper/[corrugated].

Hank Lambert, CEO of Pure Bioscience answers Packaging Digest’s questions about the SDC technology. Lambert has more than 35 years of food industry experience, including with Heublein Inc., RJ Reynolds, Nabisco Inc. and Pinnacle Foods. He has also served on boards and as a member of various food industry associations, including the Intl. Foodservice Manufacturers Assn. (IFMA), Institute of Food Technologists (IFT) and Safe Supply of Affordable Food Everywhere (SSAFE).

In short, what makes SDC different and special?

Lambert: Pure has developed a new molecule called silver dihydrogen citrate (SDC). SDC is an antimicrobial silver ion complex with a shelf life of several years. This unique combination of ionic silver (the label declares 0.003 percent silver) and citric acid (4.846 percent)—[the only active ingredients listed on the label]—allows the ion to remain in solution while at the same time making it more bioavailable for antimicrobial action.

As a platform technology, SDC is distinguished from competitors in the marketplace because of its superior efficacy and low toxicity. In addition, there is little clinical evidence it will cause the development of resistant strains of bacteria—unlike many chemicals on the market today.

Ionic silver’s multiple modes of action are believed to be responsible for its quick and broad-spectrum efficacy. SDC attracts bacteria because the citric acid component is recognized as a food source. This allows SDC to easily enter the organism through membrane transport proteins. Inside the microorganism, SDC causes irreversible damage to DNA and proteins, ceasing critical metabolic and reproduction functions and leading to the organism’s death.

Additionally, SDC is attracted to sulfur-containing thiol groups found in proteins in the organism’s outer membrane. SDC destroys protein structure and function, causing lysis of the membrane and death of the organism. This dual action makes SDC highly and quickly effective against a broad spectrum of microbes.

How did the formulation come about?

Lambert: Silver ionization has been used for years to treat swimming pools and circulating water systems; however, the ions are short lived once the power to these systems is turned off. Pure has developed a way to stabilize silver ions, allowing for long shelf life and rapid efficacy.

Why is the timing good for this product, particularly as it relates to food safety?

Lambert: There is a growing market need for more effective food safety solutions driven by: growing consumer awareness and concern as a result of increasing foodborne illness outbreaks and product recalls; increasing regulatory requirements—Food Safety Modernization Act imposing preventive controls on food processors; and an increasing retailer and manufacturer focus on the need for brand protection and risk management.

What patents are associated with SDC, especially related to packaging?

Lambert: Pure holds 12 issued patents in the U.S. surrounding SDC, its method of making and several uses of SDC. There are four pending patents in the U.S. currently and many issued and pending outside the U.S.

What form is it available—or could be delivered in—for use in packaging?

Lambert: SDC is available as a concentrated solution for use as an active ingredient or preservative in other formulations (including packaging). SDC is also formulated into ready-to-use solutions registered as surface disinfectants and food-contact surface sanitizers. Pure also intends to market an anhydrous [waterless] form of SDC for various applications.

What would this replace or supplement and why is this better?

Lambert: For packaging, we are not prepared to comment. For food-contact surfaces, it would replace or supplement ammonium- and chlorine-based sanitizers currently in use. It is better due to broader and faster pathogen kills, is non-toxic, has 24-hour residual kill, does not promote bacterial resistance and it is tasteless, odorless and colorless.

What interest is there for packaging-related use?

Lambert: We have had some interest from packaging companies for these uses, but our focus today is on SDC as a food safety solution. We have not commercialized any packaging applications and are not currently working on any. However, we would be open to discussing licensing the technology for packaging applications.

What’s ahead?

Lambert: We are aggressively marketing Pure as a food-contact surface disinfectant to food processors and restaurant chains. In addition, we are developing a formulation of SDC for direct food-contact applications. This will require FDA and USDA authorization. We estimate that the testing, submission, review and approval process will take up to 12 months.

Pure Bioscience, 619-596-8600

Tech at a glance

SDC antimicrobial from Pure Bioscience

Target markets: Currently food processors and restaurant chains

Status: Pure Hard Surface disinfectant for food-contact surfaces is currently available. A direct food-contact application for SDC is in development and is expected to be available by year-end 2014.

How an antimicrobial Trojan Horse works

SDC’s rapid and broad spectrum efficacy is largely attributed to its dual mechanisms of action and unique characteristics.

These two mechanisms, alone or in combination, make SDC a powerful antimicrobial while mitigating microbial resistance.

Bacteria are attracted to SDC because they recognize citric acid as a food source. SDC easily enters the microorganism like a “Trojan Horse” through membrane transport proteins and causes irreversible damage to the DNA and protein structure. Metabolic and reproductive functions halt and the organism dies.

SDC’s benefits are that it…

• Eliminates more than 30 harmful germs including Pseudomonas aeruginosa, Campylobacter jejuni, Staphylococcus aureus, Salmonella, MRSA, Listeria, Norovirus and E. coli, as well as H1N1 and many othears.

• Kills germs in as few as 30 seconds—conventional brands can take up to 10 minutes.

• Provides ongoing protection for up to 24 hours.

• Is odorless, non-flammable, does not irritate skin and does not cause bacterial resistance.

• Does not require hazard warnings on label; it has been assigned the lowest toxicity level by the U.S. EPA.


TAGS: Compliance
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