Tip of the Week: What We’ve Learned About Antimicrobial Packaging Material

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As 2017 nears its end, food borne illnesses related to commercially manufactured foods continues to be a primary concern for food manufacturers, regulators, and consumers. One innovation, antimicrobial packaging has been gaining interest in the food industry over the previous twelve months, though research on this method of packaging has been occurring for a number of years.

Those advocating the use of packaging films containing antimicrobial agents suggest that this type of packaging material could be more useful than the direct addition of antimicrobial compounds onto food. Antimicrobial packaging technology provides the ‘right’ antimicrobial agents to have a direct effect on targeted pathogens or microbes to prolong the shelf-life of the packed food.

The proposed usages for this type of packaging include preventing the developments of pathogens during food storage and reducing to acceptable levels of pathogens that may have entered the food stream at some point. Much scientific research has already been performed in this field, and current studies appear hopeful in advancing the use of these materials. The following information is a short introduction to antimicrobial packaging as a (potential) alternative to traditional packaging materials in both product safety effectiveness and environmental sustainability.  

Antimicrobial packaging incorporates one of two methods:

  1. Use of natural materials such as proteins to establish films/product coatings. Research performed with materials such as proteins, lipids, and polysaccharides have demonstrated effective reductions in pathogenic microorganisms [i.e. E. coli., Listeria, and Salmonella]. The key to preparation of antimicrobial films is that they must include at least one component capable of forming a suitable continuous, cohesive, and adhesive matrix.
  2. The use of synthetic films, which have ‘antibacterial materials’ embedded between laminated layers to suppress the activities of targeted microorganisms that are contaminating foods. These synthetic films may include quick-disseminating antimicrobial, which provide an immediate post-packaging protective effect, or long-term antimicrobial activation. This long-term antimicrobial activation provides antimicrobial properties for the entire shelf-life of the food product. These functions are sometimes referred to as ‘microbial-cidal’ and ‘microbial-static’ effects.

For microbial static effects, the antimicrobial substance has to possess the active function of maintaining the concentration above the minimal inhibitory concentration during the entire storage period or shelf-life in order to prevent the growth of target microorganisms. Common antibacterial substances include:

  • Antioxidants
  • Antimicrobials
  • Biotechnology products
  • Natural antimicrobials
  • Antimicrobial polymers
  • Essential oils

Currently, conventional methods of microbial control include the use of chemicals, which are increasingly less desired by consumer groups. Antimicrobial materials may be extracted from natural sources. Bacterially synthesized antimicrobial peptides known as bacteriocins, which are derived from grapefruit extracts and mustard oil have known to be the recent inventions in this field.

The most frequent antimicrobials incorporated in food packaging films are organic acid, enzymes, bacteriocins, polysaccharides and essential oils. Many studies show that the most frequently used macromolecule (polymers) for antimicrobial films formulation are proteins (whey protein, wheat gluten protein, soy protein, triticale protein, pea protein, fish protein), polysaccharides (i.e. chitosan and starch) and blends of both.

Peptides are widely recognized as promising alternatives to use as antimicrobials. The three basic methods for developing natural films are:

  1. Melting and solidification. Used on hard fats and waxes; simple coacervation, which consists in the precipitation of a hydrocolloid dispersed in this aqueous solution. This precipitation can be obtained by solvent evaporation (drying), by adding a non-electrolyte solute, and wherein the hydrocolloid is insoluble (e.g. ethanol) by an electrolyte which induces precipitation or intersection components, or modifying the pH of the solution; 
  2. Complex coacervation. Consists in obtaining the precipitation by mixing two hydrocolloid solutions with opposite electric charges that interact to form the complex polymer.
  3. Gelation or thermal coagulation. Consists in heating the macromolecules involving denaturation, gelling, and precipitation.

Essential oils are categorized as GRAS (generally recognized as safe) by the U.S. FDA. Many essential oils that are used as antimicrobial into films have names that are very familiar: bergamot, cinnamon, citronella, coriander, clove, fennel, garlic, ginger, lavender, lemongrass, oregano, pine, rosemary, sage, and thyme.

Antimicrobial agents have different activities on different pathogenic microorganisms due to their various diverse physiologies. Antimicrobial agent is integrated either directly into food particle or the packaging material, where it is released over a period of time to maintain the product's quality or the extended shelf-life. Identification of the specific microorganisms-of-concern is helpful in this regard. 

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Many materials used in antimicrobial packaging systems are safe for use in food products on their own. However, the act of incorporating those same materials into a new packaging system has created the need for continued regulatory review. It is essential to select the right package of the antimicrobial agent and environmental condition for a particular food product.