The Right Chemistry: Is all this plastic packaging necessary?
I went shopping for supper: a cucumber, cherry tomatoes, lettuce, bread, gnocchi, pasta sauce, chicken breast, blueberries and Honey Crisp apples. The plan was to make chicken schnitzel with a side of gnocchi and a salad. Dessert would be fruit.
As I was unpacking my booty, something struck me. Aside from the pasta sauce, which was in a bottle, everything else was packaged in plastic. The cucumber was wrapped in a polyethylene sleeve, my 7-grain bread probably in biaxially oriented polypropylene, the lettuce was in a re-sealable bag that I’m guessing is polypropylene. The cherry tomatoes and blueberries were in clear polyester containers, the gnocchi was vacuum packed in flexible plastic, probably composed of several layers of different polymers, the chicken was sitting on a polystyrene tray, wrapped either in polyvinyl chloride or low density polyethylene. The reason for some of this guesswork is that while solid plastic containers must be identified using the familiar recycling triangle, plastic wrap requires no such labelling. My apples also made the journey in the common tear-off polyethylene bags provided in the supermarket.
As I surveyed the scene, three questions came to mind. Is all this plastic necessary? What is the environmental impact? Is there any issue with chemicals from the plastic leaching into food?
Packaging safeguards food from outside contaminants, protects products that are sensitive to oxygen exposure, reduces waste and increases the variety of foods available. If not for proper packaging, blueberries or cherry tomatoes, replete with nutritional benefits, would not be available year round. You don’t see bins of blueberries and if you did, it would not be a pretty sight due to damage from handling and spoilage. That brings up the problem of food waste, a huge global issue. About a third of all food produced in the world, roughly enough to feed three billion people, is either lost or wasted. “Loss” occurs during production due to mould, insects, rodents, improper refrigeration and inefficient transportation. “Waste” happens when food in restaurants gets discarded, when purchased food doesn’t get eaten at home, or when produce in stores spoils or isn’t bought because of some minor blemish.
Calculations show that in North America almost a pound of purchased food per person per day ends up being discarded as a result of spoilage and excessive table waste. Appropriate packaging can reduce waste both in the store and at home. For example, that plastic sleeve on the cucumber extends its shelf life from 3 to 14 days by preventing moisture loss and contamination with airborne fungi. The biaxially oriented polypropylene ensures that no oxygen passes through to react with the polyunsaturated fats in my 7-grain bread. The gnocchi in the vacuum pack is virtually as fresh as the day it was packed because the multi-layered plastic packaging, likely polyethylene and ethylene-vinyl alcohol (EVOH), prevents moisture and oxygen from entering. Moisture is conducive to bacterial growth and oxidation of various food components results in off flavours. The tightly wrapped chicken was in no danger of contamination on its way from the store to my cutting board.
Clearly, plastic packaging can benefit retailers and consumers. But what about the environment? In an ideal world, all the plastic would be collected and recycled. But in the real world, 40 per cent ends up in landfills, 32 cent ends up cluttering the landscape and the oceans. Of the 28 cent that gets collected, half is burned for energy and half is recycled. We have to do better than that. Estimates are that without significant action by 2050 there may be more plastic by weight in the ocean than fish.
Unfortunately, not all plastics can be recycled into their original form. Polyester can, which is why discarding polyester containers, including beverage bottles, is criminal since these can be processed into new containers. My cherry tomatoes came in a container made from recycled polyester. Multilayer plastics cannot be readily recycled because their components cannot be separated, but they can still be recycled into lower value items like plastic lumber.
Chemists are hard at work developing single recyclable polymers that have the flexibility, barrier properties and strength of multilayer plastics. There is also extensive research aimed at high performance polymers that can reduce the amount of plastic needed for packaging. For example, polyethylene can be coated with a layer of silicon dioxide, essentially glass, that is only one millionth of a metre thick, giving it barrier properties similar to the multilayer plastics. The reduced weight means a much smaller carbon footprint. While paper, aluminum and glass are more readily recycled than plastics, much less plastic is needed to do the same job, meaning that transportation costs both financially and environmentally are reduced.
Of course the environmental issues have to be weighed against reducing food waste because waste also has an environmental impact. Just think of the cost of seed, the agrochemicals and the energy required to process and transport food that never gets eaten.
Obviously one can debate the environmental pros and cons of plastic packaging ad nauseam. But what about effects on our health? Plastics can harbour unreacted monomers as well as a variety of catalysts, antioxidants and plasticizers used in manufacture. One could paint a dire picture, for example, of estrogenic phthalate plasticizers migrating into food from PVC cling wraps. Without a doubt traces of these chemicals can be detected, but the amounts are trivial. Ditto for other components such as antimony trioxide used as a catalyst in polyester manufacture.
In my view, the benefits of plastics used in food packaging outweigh the detriments, mainly due to enhanced food safety, greater variety and less waste. But we do have to emphasize recycling and reduction where possible. I brought my purchases home in a reusable bag. And I did some good for the environment by reducing the need to manufacture money. I paid with plastic. And if you are interested, the schnitzel and gnocchi were yummy, the salad fresh, the blueberries tasty and the apple crisp. That’s because it had been protected with a wax spray. But that’s another story for another time
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