Aluminium with a non-stick coating

Aluminium with a non-stick coating

Non-stick aluminium utensils offer all of the benefits of unfinished aluminium utensils (manoeuvrability, ability to conduct heat) as well as non-stick performance.

The non-stick coating used mainly for coating aluminium cooking utensils is made using PTFE (polytetrafluoroethylene). PTFE, also known by the name Teflon, is an inert polymer with high thermal and chemical resistance.
Recently, the use of Teflon as a material for coating cooking utensils has been questioned, linked to inaccurate information resulting from having confused another compound (PFOA - perfluorooctanoic acid) with PTFE.

In particular, non-stick coatings appear to be free of PFOA. Non-stick coatings have been around for more than 40 years and are safe for their intended use. European regulatory agencies such as the EFSA (European Food Safety Authority), the French agency for food safety AFSSA, U.S. agencies such as the Food and Drug Administration (FDA) have stated that non-stick coatings made with fluoropolymers are safe for their intended use in cooking. The FDA also reiterated that particles of non-stick material, even when accidentally ingested, do not constitute a health risk. Due to their chemical inertness, they are not transformed in any way. These particles simply pass through the organism unaltered, therefore proving to be harmless to our body. For these reasons, the use of scratched cookware poses no risk to the health of consumers, however it is recommended that they be replaced simply because they cease to perform their specific non-stick function.

As evidence of its chemical inertness, and therefore of its safety, it should be noted that the fluoropolymer used in non-stick coatings is also used in surgical procedures to coat pacemakers and in thoracic surgery.

Pans with non-stick coatings can be heated to temperatures of up to 260°C without damaging the coating. This temperature is much greater than that required to boil, fry or cook in the oven.

For example:

  • water boils at 100°C,
  • meats are normally browned at temperatures ranging from 200 to 240°C,
  • in the oven, the highest temperatures used for cooking poultry or vegetables are around 230 °C. Cakes and biscuits are usually baked at temperatures between 160°C and 200°C.

It is important to bear in mind that the maximum cooking temperature recommended for maintaining the nutritional value of food in the absence of liquids, such as grilling, is 250°C.

The use of non-stick utensils offers the following advantages:

  • 1. Safety for human health since the food does not stick to the bottom, preventing the development of harmful or even toxic substances due to the combined effect of overheating and dehydration.
  • 2. A healthy diet, since non-stick pans allow you to cook without oil and fat.

In September 2011, the italian magazine Altroconsumo examined various non-stick pans, which they subjected to rigorous tests. In addition to the various benefits the various models were shown to provide, the study highlighted the lack of health risks. Even when the coatings were scratched, no release of hazardous substances was detected.

Non-stick coatings can be applied to cooking utensils using different techniques.
The technique that results in the best quality, and therefore the longest-lasting wear, is spray application.
Among the coatings applied by spraying, additional distinctions can be made that differentiate the quality levels based on the total thickness and the number of layers applied.
The duration and performance of a non-stick utensil essentially depends on the thickness of the pan and the quality of the coating. Overheating, abrasions and scratches are the factors that influence the duration the most.
A quality coating applied to a thin pan is a contradiction since the utensil will easily overheat and the resulting hot spots will compromise even the best coating. All of the previously mentioned considerations regarding the thicknesses of aluminium utensils also apply to aluminium non-stick utensils, with the addition of the fact that a sufficiently high thickness acts as a safeguard for the thermal coating itself.
A considerably important factor for ensuring the duration and quality of a non-stick utensil is the aluminium body.

In particular, it may be obtained using different technologies, of which two are the most used:

  • 1. Cold plastic deformation (drawing, stamping)
  • 2. Die casting

In the first case, the item is made by the cold deformation of an aluminium sheet that is produced from lamination. In the second case, the item is made by injecting aluminium in its molten state into a metal mould. The alloys used for making utensils through die-casting contain fluidifying substances, such as silicon, zinc, copper and tin. For this reason the aluminium content is usually between 86% and 87%.

In the case of utensils obtained by cold deformation, the content of aluminium is between 98% and 99.5%, an indicator of high purity.

For this reason, the unpainted parts of die-cast items, when placed in the dishwasher, tend to oxidize very quickly, releasing a black patina.

On the other hand, die-cast containers offer the advantage of being made with an extremely high thickness that cannot be obtained using other techniques with the exception of cold forging which, thanks to the use of powerful hydraulic presses (5000 tonnes), distribute the material at cold temperatures in a differentiated manner, concentrating it in the most important points such as the bottom.

Cold forged aluminium has a high purity level of the alloy used because it is produced by laminating a primary casting plate. As a result, the production cycle is beneficial in terms of emissions and energy consumption compared to other production techniques. The production process is also important for obtaining the quality of the non-stick coating.

In the case of items made by die-casting, during the casting process inclusions of air can occur that are released later from the utensil during the cooking process. This results in a phenomenon known as blistering, or the presence of bubbles in the non-stick coating.

To ensure a longer duration of non-stick coatings, it is recommended not to use sharp metal utensils, not to cut the food inside the cookware and to use cooking utensils made of wood, plastic or silicone. It is always recommended to use a heat source that is suitable for the dimensions of the bottom of the utensil and to centre the utensil over the heat source. Furthermore, it is always sufficient to cook over a moderate flame.

In some cases, a layer with a high surface hardness of titanium oxides is deposited between the aluminium substrate and the nonstick coating to give the latter greater resistance to scratching. The latest innovations to join the world of coatings are the white non-stick coatings and the stone-look coatings. The light colour of the white non stick coatings is particularly appreciated in the professional cooking field, allowing chefs to better monitor the degree of transparency of the food being cooked. Both the white and the stone-look coatings combine the features of a traditional non-stick coating with a special appearance.
All non-stick coatings made using PTFE do not contain nickel, heavy metals or PFOA.

Laws and regulations on non-stick aluminium: Italian Ministry Decree of 21 March 1973 and subsequent amendments; Ministerial Decree no. 220 of 26 April 1993 and subsequent amendments; EEC Directive 2002/72/EC and subsequent amendments.

The federal regulation of the American Food & Drug Administration on fluoropolymer-based materials intended for use in contact with food can be accessed from the following link.
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=177.1380

The recommendation of the German Federal Institute for Risk Assessment (BfR) on materials intended to come into contact with food, in this specific case on the polymer coating systems used in the field of cookware, can be downloaded from the following link.
http://bfr.zadi.de/kse/faces/resources/pdf/510-english.pdf

Guide to the choice of materials for the cooking of food

All the materials mentioned in this guide are regulated by the following laws, directives and guidelines that can be downloaded from the following links of the EFSA (European Food Safety Authority) and the COE (Council of Europe): downloadable at the following link:

EFSA COE Download the pdf guide