The Hidden Enemy. Bacteria on Stainless Steel and the Importance of Surface Finish
Unseen bacterial growth is high on our priorities with a renewed focus on ensuring equipment is designed to enable the highest level of cleanliness down to a microbial level.
With Stainless Steel as the standard base for all processing equipment due to its mechanical and chemical properties, it is important to understand that not all Stainless Steel is equal. The surface finish is critical to creating the most hygienic equipment for our industry. Three main surface treatments seen in our industry are; Sand Blasting, Sanded and Electro Polished.
When bacterial cells attach to a surface, they produce extracellular polymers that anchor the cells and provide a favourable environment for growth and subsequent attachment of more bacteria, other microbes, and debris. The composite is a biofilm that is resistant to cleaners and sanitizers creating issues for manufactures with the potential for microbial growth, especially in hard to reach areas of machines including welded corners.
Current plant sanitation methods rely on physical and chemical treatments for removal or killing of bacteria to control contamination, however, it is important to understand how bacteria attaches to surfaces, forms biofilms and how quickly this can grow and spread.
Studies using poultry protein show how bacteria will attach to different surface treatments and subsequently grow over time, highlighting the best practice of using Electro Polishing within our industry. A recent study took four different surface treatments, (A) untreated as a control, (B) Sand Blasted, (C) Sanded and (D) Electro Polished.
The Stainless steel that had been Electro Polished showed significantly fewer bacterial cells and biofilm formations than all the other treated surfaces. The results of this test show that a Sanded Surface has over 10 times the number of dispersed cells over Electro Polished with Sand Blasted showing 13 times the level of cells.
The use of Electro Polishing within the food industry is not new and is the standard within certain applications and areas including gastro trays and the bowl of bowl cutters. However, some manufactures are taking the use of Electro Polishing further to enhance the level of hygiene quality. SCHIWA are one such company that choose to Electro Polish the whole of their industry leading High Speed Slicing Systems. Their reasons are as follows:
Reduced bacterial attachment on all surfaces
Chemical washes cannot permeate lesser finishes
Swab tests prove lower bacterial growth on SCHIWA systems
Surface finish continuity across whole machine – including welded areas
Machine OEE: Washing & drying time reduced by 40%
Improved aesthetic - Machine looks newer for longer
Retained valu
Example of a retail ham slicing line from Schiwa highlighting the Electro Polished finish.
Jens Schindler – Innovation Director at SCHIWA explains that they considered the need for Electro Polishing in detail and concluded that any other surface finish was not good enough for the technically advanced industry of High Speed Slicing, especially for high risk products such as cooked or cured ready to eat meats, hams and cheeses.
“Particular attention was given to welded seams which cannot have the same surface treatment as the main surface with any other treatment, as a result these areas are often the culprits for bacterial growth. Electro Polishing eliminates this potential for contamination and gives our customers the reassurance that every area of the machine maintains the highest standard of surface finish. In addition, due to a ‘lotus effect’ of Electro Polishing our customers see a huge reduction in their washing and drying time of our systems, enabling them to run for longer in production with less down time due to routine hygiene. We also find that because an Electro Polished machine always looks new, operators and site engineers do look after the machine better which prolongs our market leading OEE Availability significantly.”
Long standing SCHIWA customer Norseland confirms surface finish and build quality were key influences in their decision to purchase SCHIWA. Tony Helyar, Continuous Improvement & Capital Projects Manager from Norseland explains:
“The surface finish and attention to detail on a Schiwa is clearly of a higher quality and is one reason we chose to invest in Schiwa for our High Speed Slicing line. Our hygiene routine is quick and efficient which enables us to produce more and be more profitable and I personally value that even our 14 year old line still looks like new.”
To learn more about SCHIWA and the advantages their increased level of hygienic design and finish can give you, visit schiwa.de, technikfoodsystems.com or contact Jack Ridel at Technik Food Systems in the UK/Ireland on +44 (0)1637 85486 .
Reference: Surface Finishes on Stainless Steel Reduce Bacterial Attachment and Early Biofilm Formation: Scanning Electron and Atomic Force Microscopy Study J. W. Arnold and G. W. Bailey
Additional reading on Electro Polishing and its advantages can be found here:
