Smart packaging can help extend food shelf-life, enhance product quality, ensure safety, and monitor product performance through the supply chain. Professor Pierre Pienaar outlines the variations of these products and what they can do.
There are two varieties of smart packaging. The first, active packaging, is designed to extend the shelf life of products. It can do this in a number of ways, such as by releasing or absorbing substances which extend the duration of product quality.
The second type, intelligent packaging, is an extension of active packaging. It can monitor the product’s condition and communicate any changes to the consumer. It should provide more reliable information than just the expiry date printed on the packaging; and should monitor certain aspects of a food product (for example shelf life) and report information to the consumer.
Some of the chief purposes of intelligent packaging systems are improving the quality or value of a product, increasing convenience, and providing tamper or theft resistance.
There are currently three major types of intelligent packaging technologies available, namely sensors (biosensors, gas sensors), indicators (temperature, freshness), and data carriers (barcode, RFID). There is a great variety of indicators in each of these types, as well as much opportunity for further development of this technology.
For example time-temperature indicators (TTI), which are among the most commonly used types, can be classified as biological, physicochemical, chemical, enzymatic, diffusion-based, or polymer-based.
Diffusion-based TTI is a widely used physical TTI. Fick’s law allows the application of diffusion in TTI. The diffusion rate of a liquid material would be higher at higher temperatures, and its distance of diffusion shows the total influence of environmental temperature. This is the working principle of diffusion-based TTI.
The applied principle of chemical TTI is a temperature-dependent chemical reaction. This type of TTI includes polymerisation-based and photochromic-based redox reaction-based TTI, depending on the different reactions it utilises.
This relates to biological reactions referring to enzymes or microorganisms. Enzyme based indicators present colour change caused by the reaction between enzymes and substrate with a pH change. One part includes lipolytic enzyme solution, lipase and a dye with pH indication. The other part is a substrate, predominantly triglyceride. The indicator will be activated when the gap between enzyme and substrate is broken so that two parts are mixed.
This type of intelligent packaging contains thermochromic ink consisting of dye, reagent and solvent. UV light activates the indicator because the ink absorbs photons with certain wavelengths, and activates them to excited states and forms free radicals or ions.
Controlled permeability packaging
Controlled permeability packaging (CPP) is a less expensive alternative to Modified Atmosphere Packaging (Pictured). In this type of packaging, no gas is flushed out or injected, but rather the produce is packaged within a film that controls the quantity of oxygen and carbon dioxide flowing into and out of the package. This type of packaging is suitable for small scale suppliers in developing countries, where pure MAP might result in the product cost being too high for the average consumer. This packaging produces shelf life results close to, but not as high as pure MAP.
CPP could be a good solution to food waste, especially in developing countries where suppliers may not be able to afford MAP machinery and processes, and where consumers may not be able to afford MAP produce.
Nanotechnology is a form of active packaging that utilises bio-nanocomposites consisting of nanoparticles embedded into a biopolymer matrix – with dimensions less than 100 nm.
The antimicrobial action of silver nanoparticles is attributable to their high surface area-to-volume ratios which favour their interactions with microbial cells. These silver nanoparticles cause direct damage to the cell membranes of harmful microorganisms, by interacting with negatively charged bio macromolecular compounds with disulphide or sulfhydryl groups and nucleic acids. This results in cell membrane deformation, inactivation of metabolic processes and cell death.
Nanoclays consist of montmorillonite silicate layers also known as nanoplatelets which are in a stacked arrangement with a nanometric thickness of 1 nm and a structural dimension of 100 nm.
These nanoclays are incorporated into the matrices of a polymer to delay the flow of gases such as oxygen and carbon dioxide from the external environment to the internal environment. Nanoclays exhibit excellent barrier properties due to their high rigidity, aspect ratio and affinity as a result of the interfacial interaction between the matrices of the polymer and the dispersed nanoclay.
Nanosensors are excellent microorganism detectors as they are able to monitor the safety and quality of food products at various stages of the food supply chain. These sensor systems have the ability to accurately detect food spoilage or microbial contamination in food by interacting with the external and/or internal environment of the food, thus producing a response in the form of a visual signal such as colour indicators on nanosensor labels which correlate with the current state of the food product.
Professor Pierre Pienaar (FAIP, CPP) is Education Director at The Australian Institute of packaging (AIP) and President of The World Packaging Organisation (WPO).