How would you like a side of perfluorooctanoic acid with your popcorn?
How would you like a side of perfluorooctanoic acid with your popcorn?
Answer: The key to non-stick cookware coatings is a slippery ingredient called polytetrafluorethylene (PTFE). Cookware isn’t the only product that benefits from this plastic polymer’s attributes; the medical profession also uses it. So, how safe is it and the other chemicals involved in its production?
PTFE belongs to a group of perfluorochemicals known for being highly stable and resistant to degradation. It has a high melting point (327°C) and is resistant to many chemicals, hence its use as a cookware coating.
The polymer is also biologically inert and nonbiodegradable in the human body. It is also used to coat pacemakers and line the tubes that replace arteries and in facial plastic surgery.
Other perfluorochemicals are used to make paper products and packaging more resistant to moisture and oil – for example, microwave popcorn bags are typically lined with these types of polymers.
However, large-scale population studies have found measurable levels of certain perfluorochemicals, such as perfluorooctanoic acid (PFOA), in the blood of fluorochemical production
workers and the general population. This acid is a processing aid used in the manufacture of PTFE.
The International Agency for Research on
Cancer classifies PFOA as “possibly carcinogenic to humans”, and as it takes a number of years for our body to excrete this chemical, we don’t want it in our food supply.
In 2005, the US Food and Drug Administration investigated levels of PFOA and other fluorochemicals in a number of food-contact materials and their potential for migration into food. They found PTFE-coated cookware was a negligible source of perfluorochemicals, such as PFOA, even under extreme heat. The highest migration levels were from microwave popcorn bags to their contents. The researchers concluded fluorochemical-coated paper posed a greater potential contamination risk than non-stick cookware.
In the decade since, the US’s Environmental Protection Agency has worked with key manufacturers to phase out the use of PFOA in food and non-food-related products by the end of 2015. Internationally, the Organisation for Economic Co-operation and Development has also been working towards the phasing out of perfluorinated chemicals.
Question: Why is the energy value of food given in kilojoules on packaging and elsewhere? Until relatively recently, calories were used and they’re much easier to work with.
Answer: Even our national game of rugby was altered when the metric system was introduced in 1976, with the 25-yard line from goal becoming a 22m line. The Weights and Measures Amendment Act became law on
December 14, 1976, so it’s been 40 years since metric use became compulsory, and all goods must be sold in metric units. Although calories are a metric unit, they were superseded in the International System of Units by the joule as the recognised unit for energy, work and heat.
Our Food Standards Code requires food manufacturers to print the energy content of their products in kilojoules on the nutrition information panel. However, manufacturers can also add the energy content in kilocalories – 1 kilocalorie (kcal) is equal to 4.186 kilojoules (kj) – because previously kilocalories were used as the energy unit for food.
Just to confuse matters, kilocalories are frequently referred to as calories. So although dieters may be familiar with advice to choose snacks containing 100 calories or fewer, such as a banana, these foods actually have 100 kilocalories or 420 kilojoules.
A significant benefit of thinking in joules is that scientists and engineers are then able to communicate using a common energy unit. Many nutrition scientists no doubt feel your pain, but it seems unlikely we’ll revert to using calories as an energy unit specifically for food.