Stainless steel appliances–more than just looks

Source for featured photo: Kitchen Unit Doors

Stainless steel appliances have traditionally been used in professional kitchens, but they have been gaining popularity in the average homes due to their modern look and resistance to bacteria. However, the price for stainless steel appliances can be 10-30% higher than average appliances [1, 2]. What gives stainless steel appliances their antibacterial properties? Are they worth the extra cost?

The facts

Stainless steel appliances have been favoured in professional kitchens and food processing facilities primarily because of their corrosion resistance, durability, and cleanliness factor (i.e. easily show fingerprints). However, stainless steel on its own doesn’t actually possess antibacterial properties [3]. In fact, it is the coatings or additions (i.e. alloyed elements) that are added to the stainless steel that makes it antibacterial.

For example, stainless steel containing silver (as little as 0.04 mass %) has been shown to exhibit antibacterial properties [3]. Silver ions can penetrate the bacterium’s cell wall and interact with its DNA and proteins, causing damage or even death of the cell [4]. Specifically silver ions can i) absorb onto the bacteria cell’s surface and damage the cell membrane and proteins; ii) absorb into the bacteria and inhibit cell enzymes by interfering with cell DNA; iii) cause oxygen to be generated on the stainless steel surface and interact with cell enzymes, destroying bacteria cells in the process [3].

Notably, silver-alloyed stainless steel has been reported to exhibit antibacterial properties against common sources of foodborne illness such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) [3]. E.coli originates from the gut of humans and animals and can be found in raw and undercooked meat and poultry [5, 6]. S. aureus on the other hand, originates from the skin and noses of animals and humans and can be found in raw foods as well as unpasteurized milk and dairy products [5, 6].

How does stainless steel compare to other materials?

An antibacterial surface is one that shows less than 1% of the bacteria compared to a comparison product after 24 hours [3]. Thus, bacteria can still exist on antibacterial stainless steel appliances, just at a much lower quantity compared to the average appliances.

Just because regular appliances may be more proned to bacteria, it doesn’t mean you should replace them all with antibacterial stainless steel ones. It just means they should be cleaned/sanitized more frequently.

There are different methods to effectively remove kitchen germs. On typical metal surfaces, rubbing the surfaces with detergents dissolve food and microbial material [7]. Subsequently sanitizing the surface with dilute bleach will even further eliminate any further bacteria [7].

For wooden or plastic surfaces, microbes can be scrubbed off with soap and water [7]. It is important to realize that bacteria is known to accumulate below wooden surfaces [7]. Although, the dangers of such bacteria are much lower as they are below the surface and generally will not have a chance to come into contact with food to contaminate it. On the other hand, plastic surfaces containing knife scars (e.g. cutting boards) are resistant to decontamination by hand washing [7].

Bottom line

To prevent bacteria formation, surfaces must stay dry and abrasion free (i.e. smooth, crack free). The combination of stainless steel’s corrosion and wear resistance with silver’s antibacterial properties is what makes antibacterial stainless steel (e.g. silver-alloyed stainless steel) particularly desirable for the kitchen appliances.

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References
[1] General Electric Company. (2011). GE Profile™ ENERGY STAR® 25.6 Cu. Ft. Side-by-Side Refrigerator [Online]. Available: http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=PSHF6YGZWW

[2] General Electric Company. (2011). GE Profile™ 30″ High Performance Range Hood
[Online]. Available: http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=JV636HSS#FEATURES

[3] T. Yokota et al., “Silver Dispersed Stainless Steel with Antibacterial Property,”  Kawasaki Steel Technical Report, vol. 46, pp. 37-41, June 2002.

[4] Q.L. Feng et al., “ mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus,” Journal of Biomedical Materials Research, vol. 15, pp. 662-668, December 2000.

[5] The Association for Science Education. Microbes and Food [Online]. Available; http://resources.schoolscience.co.uk/sgm/sgmbugs2.html

[6] National Digestive Diseases Information Clearinghouse. (2007). Bacteria and Foodborne Illnesses [Online]. Available:
http://digestive.niddk.nih.gov/ddiseases/pubs/bacteria/#1

[7] J. Raloff, “Sponges and Sinks and Rags, Oh My!” Science News, vol. 150, pp. 172-175, September 1996.

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One response to “Stainless steel appliances–more than just looks

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