Sunday, July 24, 2011


From time immemorial, chemicals have been in use for preserving foods for long time. Sugar and salt are the most ancient chemical substances used in food preparations for preventing bacterial spoilage while vinegar became an accepted preservative later. Emergence of synthetic chemicals like sulphites, chlorine, sorbic acid, propionic acid, paraben, medium chain fatty acids etc provided the industry with more options for deploying in different food products without imparting any odor of their own. Based on the antimicrobial properties of some of these chemicals, active packaging systems are gaining popularity with the industry. At present most applications of active antimicrobial packing are more visible for culture media preservation. But for packing bread or cheese active antimicrobial packaging materials are available based on LDPE and sorbates. Here is a take on this emerging area of food packaging.

"When antimicrobial agents are incorporated into a polymer, the material limits or prevents microbial growth. This application could be used for foods effectively, not only in the form of films but also as containers and utensils. Food packaging materials may obtain antimicrobial activity by common antimicrobial substances, radiation, or gas emission/flushing. Radiation methods may include using radioactive materials, laser-excited materials, UV-exposed films, or far-infrared-emitting ceramic powders. However, irradiation sterilization of food packaging materials is not yet permitted by the Food and Drug Administration. Gas emission/flushing controls mold growth. For examples, berries and grapes are stored in produce boxes, palletized and stretch wrapped, then flushed with sulfite to prevent fungal
It is easy to use these types of bulk gas flushing and controlled/modified-atmosphere technologies. However, there is no commercial material which contains or releases sterilizing gases such as sulfite. Sachet systems have been used to control the gas One of the earliest attempts in using packaging material as a protective medium to prevent microbiological spoilage is sorbate or propionate coated wrapping materials for fresh bread which is susceptible to fungal attack within 2-3 days of storage".

"Active antimicrobial packaging could have potential for extending the shelf life of packaged foods. There is therefore significant interest in finding organic or inorganic antimicrobial compounds for use in active polymeric packaging suitable for foodstuffs. Silver nanoparticles (AgNPs) have antibacterial properties and are widely used in biomedical, food packaging and water treatment applications. The antibacterial activity is mainly related to the strong inhibitory and bactericidal effects of silver ions and to its interaction with sulfur-containing proteins found in respiratory enzymes of bacterial cells. AgNPs bind to the bacterial cell wall and membrane, inhibiting the respiratory process and cell division, causing cell death. They have shown growth inhibition of various pathogens including Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. The antibacterial effectiveness of polymeric nano composites strongly depends on the hydrophilic nature of the polymeric matrix and on boundary conditions, such as pH and ionic strength of the release solution. The use of silver in highly filled systems is a viable approach for avoiding direct contact with food and thus meeting EU safety regulations for the presence of silver ions in food matrices. Inorganic phyllosilicate clays have been used as a support for AgNPs to produce a new class of antimicrobial systems with improved stability and release kinetics".

Silver nano particle embedded plastics will be a hit with the industry, if it works as claimed. There are 3 active packaging construction models based on different mechanisms like release ( for gases), absorption the ones based on release mechanism can be effective only for liquid medium and immobilization incorporating chemical preservatives. obviously Silver nano particle based anti microbial plastics will have to constructed on the immobilization technique. How far these packing materials can be depended upon for 100 % reliability is not known. Probably the current level of development may not result in ready availability of commercial products to the user industries in the immediate future. Besides the controversy regarding the safety of nano technology needs to be resolved satisfactorily for the consumer to willingly accept such packaged foods


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