By Carol Zweep
Active and intelligent packaging is a sector that continues to grow on a global basis. Active packaging changes the condition of the packaged food to extend the shelf life, or improve food safety or sensory properties of the packaged foods. Active packaging can be divided into absorbers (scavenging systems) and emitters (release systems).
Antimicrobial packaging is a form of active packaging that releases compounds (“active agents”) to reduce, inhibit or slow the growth of microorganisms that may be present in the packaged food or packaging material. The use of these active agents maintains food quality and reduces the need for preservatives and additives. Active agents can be incorporated into packaging material, coated/adsorbed onto packaging surfaces or placed within elements such as sachets, pads or labels. Antimicrobial systems can work by direct contact with the food surface or they can control migration of non-volatile agents or emission of volatile compounds into the headspace atmosphere surrounding the food.
Use of plant extracts and oils with known antimicrobial properties (such as oregano, clove, rosemary, white thyme, tea tree, coriander, sage, and laurel) is generally recognized as safe, but the concentration may need to be higher to be effective for keeping processed foods fresher longer. Future work will focus on antimicrobial compounds that are bound onto the polymer. This would avoid detachment from the packaging material to maintain antimicrobial properties and avoid regulatory hurdles related to migration of chemicals into food.
One type of scavenging system is oxygen scavengers or oxygen absorbers. They are chemical compounds that react and bind with oxygen. They work by preventing oxygen in the atmosphere from getting into the package and reacting with the product. They can also remove headspace oxygen or dissolve oxygen from the product. Elimination of oxygen in the package can reduce aerobic microorganism and mold growth and also prevent oxidation of products that result in off-flavours and odours, discolouration and nutrient degradation. Oxygen scavengers can be placed into sachets and incorporated directly into films, bottles and closure systems.
Future work focuses on the use of natural and biological oxygen scavengers entrapped in the polymer matrix. Possible scavengers include food-grade antioxidants such as vitamin E (-tocopherol) and vitamin C. The use of immobilized aerobic microorganisms as a mechanism for oxygen scavenging has also been suggested. Development of more scavengers that are triggered by activation will prevent loss of the scavenging capacity of the package. An oxygen scavenger that can indicate the level of oxygen present will enable it to act as both an active and intelligent package component.
Active packaging is successfully being used in the U.S., Japan and Australia, but is limited in other countries, including Canada. The food industry is reluctant to embrace active packaging due to legislative restriction, lack of knowledge about consumer acceptance, uncertain efficacy of systems, and unclear economic and environmental impact.
With interest in eliminating packaging waste due to environmental concerns, edible packaging is an attractive alternative. Edible packaging is non-toxic, biodegradable and made from a renewable resource. Much academic research is devoted to developing new edible materials that will replace some of the commercial applications of plastics. The major ingredients that can be used for edible film include lipids (waxes, fatty acids, acylgycerols), polysaccharides (cellulose, alginate, pectin, chitosan, starch, dextrin) and proteins (gluten, collagen, corn zein, soy, casein, whey protein). The edible film or coating should have qualities such as acceptable colour, odour, taste, flavour, and texture. It must also adhere to food, dissolve in the mouth (but not during handling) and be safe to consume.
There are many current applications of edible films and coatings in the food industry. Coatings with a blend of vitamins and minerals prevent browning and softening of cut fruit. Calcium-reactive pectin has been used for fried foods to maintain moisture and limit fat uptake resulting in a lower-fat finished product. Modified starch films can be used to reduce purge, adhere flavour and enhance colour for precooked ready-to-heat meat products. Nuts can be coated to retard oxidation but also to prevent oil migration into surrounding food (such as nuts in chocolate). Fragile foods such as breakfast cereals and freeze-dried products can be coated to improve integrity and reduce damage. For low-fat snack foods, edible coatings can be used as seasoning adhesives without the use of oil. Expensive dry ingredients can be pre-measured into pouches that facilitate the batching process.
Bioplastics are plastics in which all carbon is derived from renewable feedstock.
Compostable material such as polylactic acid is made from renewable resources such as corn, beets, wheat, and sugarcane. Bioplastics can also be made within microbes (i.e. polyhydroxyalkanoate). There are new biopolymers being developed with new functionality (i.e. polyethylene furanote). Bio-based intermediates have been used to make conventional plastics (i.e. production of polyethylene from sugar cane).
The use of food-based feedstock has been a point of criticism for bioplastic packaging. Plant-based raw materials are now being sourced from non-food feedstocks like agricultural, forest and municipal waste. The challenge for non-food feedstock is the economics of the supply chain management (i.e. storage, handling and shipment of low-density biomass) and cost-effective breakdown of the biomass into its constituent sugars.
It is also important to think about recovery in addition to sustainable sourcing since bioplastics are currently ending up in landfill. There is a shift from composting to more energy-favourable recycling as an end-of-life option. The use of polymer markers or new sorting technology will assist with the issues surrounding the recovery of these materials.
The environmental impact of bioplastics is often debated since there are many different metrics for sustainable packaging (i.e. energy consumption, greenhouse gas emissions, etc.). This is also complicated by the fact that many different types of bioplastics exist, each with different environmental strengths and weaknesses. Challenges with development and widespread acceptance of bioplastics include desire for sustainably grown biomass, need to develop recovery infrastructure, concern over contamination of recycling systems, and lack of consumer awareness and education.
Carol Zweep is Senior Manager, Packaging, Product Development, and Compliance for NSF International. She can be reached at firstname.lastname@example.org.