By: Mr. Dattatraya Bharat Latpate*
Antimicrobial food packaging is a form of packaging that can kill or inhibit the growth of microorganisms in the packaged product and, thus, serves to extend the shelf life of perishable food products as well as enhance food safety standards.
These are of three types:
- Chemical Agents
- Natural Agents
These are of two types:
Food Grade, which can be incorporated into products in the following ways –
- Mixed with the food ingredients;
- Incorporated into the packaging material; or
- Inserted into the head space between the packaging material and the surface of the product.
Non Food Grade –
- Used only in packaging material.
Natural Agents: These are:
- Herb extracts
Herb and spice extracts contain multiple natural compounds and are known as wide spectrum antimicrobial agents.
These agents hold an edge over other agents used in antimicrobial packaging as these are edible components.
These are obtained from various microorganisms. They produce bacteriocins and non-peptide growth inhibiting chemicals such as reuterin. Now days, these are used less frequently. However, in the future, probiotics may become more popular due to the safety benefits offered by, and effectiveness of the same.
The antimicrobial packaging system, essentially, consists of the following:
- Food product in the package;
- Packaging material or the package itself; and
- Target microorganism used in the packaging.
Factors which determine system design: Casting process conditions-
- Characteristics of anti-microbial substances
- Storage temperature
- Physical properties of packaging material
An antimicrobial agent performs specific inhibitory activities, and has in place particular mechanisms to target different microorganisms. Thus, antimicrobial agents are chosen and used according to the nature of the target microorganism. Microorganisms are distinguished using the following characteristics:
Whether they are aerobes or anaerobes;
- Cell wall composition;
- Growth stage;
- Optimal growth temperature; and
- Whether they present acid or osmosis resistance.
Action of Microbial Agents
Microbial agents inhibit the activity of microorganisms using one of two methods:
A microbiocidal antimicrobial system may kill the target microorganism when the antimicrobial concentration goes above the minimum inhibitory concentration (m.i.c) for a length of time.
Microbiostatics agents can inhibit the growth of microorganisms above a certain critical concentration (i.e. m.i.e).
Functioning Mode of Antimicrobial Agents
Antimicrobial agents are transferred to the food product using two different means. These are:
- Non-Volatile migration
- Volatile migration
Non- Volatile migration
The mass transfer of non-volatile anti-microbials is based on the process of diffusion migration. Nonvolatile agents are positioned in the packaging material itself, or in the space between the package and the surface of the food. Examples of this system include cured or fermented meats and sausages buttered with antimicrobial agents, natural cheeses sprayed with potassium sorbate before packaging, antimicrobial coatings on fresh produce, etc. Advantage of this system is the simplicity of its design.
Volatile Migration: In this case, the volatile agent is initially placed in the packaging material – whether it is a film, container, sachet or tray. After packaging the food, the volatile agent is vaporized into the headspace such that it reaches the surface of the food and is subsequently absorbed by the product. Used effectively for highly porous foods, as well as powdered, shredded, irregularly shaped or particulate foods such as ground beef, shredded cheese, small fruits, etc. Advantage of this system is that it draws from naturoceutical research because of which it is more easily accepted by consumers and regulatory government agencies.
COMMERCIALIZATION OF ANTIMICROBIAL PACKAGING
Food products have complex compositions which determine the types and forms of antimicrobial packaging that can be used in different cases. There are, thus, many factors to be considered in the commercialization of antimicrobial packaging systems. These include:
- Technical factors;
- Regulatory, marketing and political factors.
- Compatibility of process conditions and material characteristics
- Physical properties of packaging material
- Controlled Release Technology
- Extra dvantages
Regulatory, Marketing and Political Factors
The use of antimicrobials in food product packaging should adhere to the guidelines set by regulatory agencies.Various marketing factors are involved in the commercialization of antimicrobial packaging systems:
- Consumer acceptance
Primary goals of an antimicrobial packaging system are to:
- Ensure food safety;
- Quality maintenance; and
- Extend the shelf life of product.
Today, food security has become a big political and scoio-economic issue across the world; antimicrobials can play an important role in dealing with the growing challenge of food insecurity.
Different types of antimicrobial agents:
- Naturally occurring edible coatings and films
- Antioxidants used as antimicrobials
- Chemicals used as antimicrobials
Naturally Occurring Coatings and Films
Naturally occurring coatings and films are of different types. These include:
- Lacto peroxidase system
- Allyl isothiocyanate
Advantages of using naturally occurring coatings:
They are effective carriers of antimicrobials. Food can be simply treated with these compounds through direct applications such as –
Antioxidants as Antimicrobials
BHT is a small, mobile antioxidant that can be imported into packaging films. It has been shown to be effective in extending shelf life of oat meal based cereals when used in high concentration (around 0.3%) in HDPE films. Vitamin E is regarded as having the most potential when used as an antimicrobial as it can be dissolved into polyolefins and does not breakdown when processed into film form. One Danish company is said to already be using vitamin E in a cheese wrappers to scavenge for oxygen within the pack.
Chemicals as Antioxidants
Different types of chemical agents are used as antioxidants. Some of these are:
- Potassium sorbate is used in low density polyethylene (LDPE), which is used for packaging of dairy products (especially cheese).
- Calcium sorbate is used in paper for the packaging of bread.
- Propionic acid is used with chitosan as an antimicrobial agent in water.
- Acetic acid and chitosan are combined and used in the packaging of water.
- Sorbic acid anhydride in polyethylene is used in the packaging of culture media, a substance used in laboratories.
- Benzoic acid anhydride in polyethylene is used in packaging materials of fish fillet products.
- BHT with high density polyethylene is used for the packaging of breakfast cereals.
- Ethanol in silicon oxide sachets, which are used for packaging of bakery products.
New Developments in Antimicrobial Packaging
- New techniques have been developed for mobilizing antimicrobial agents on plastic substances.
- The Department of Food Science at Cornell University has been undertaking work on attaching bioactive materials and enzymes to polyethylene films with potential applications in food packaging.
- A team at the University of Massachusetts developed an additive made from a mix of organe and cranberry which is able to inhibit the growth of listeria in processed meat.
- The Spanish Institute of Agri-chemistry and Food Technology has developed a new antimicrobial packaging solution that uses strawberry extract to combat the growth of bacteria in berries.
A team at Oregon State University developed an edible antimicrobial film by combining two key ingredients – a fiber from shellfish (chitosan) and a protein from egg white (lysozyme).
* Food Safety and Quality Officer, Mondelez India Foods Pvt. Ltd.