Coating Applications for Food, Flavors, and Fragrances

A collaborative research effort from the Department of Biomedical and Nutritional Sciences at the University of Massachusetts, Lowell and the Agricultural Research Service at the United States Department of Agriculture* showed the benefits of using Dursan on stainless steel as a means of reducing listeria biofilm formation.

The group investigated 304 stainless steel with a variety of surface textures and FDA compliant coatings.  Of all the treatments, the Dursan® process applied to a native 304 surface showed the best results.  Dursan also showed promise on a textured surface, eliminating the need for the change in topography. 

The biofilm formation was quantified in two different ways: CV staining and plate counts.  CV staining shows the total mass of biological substance that was on the sample surface while the plate counts show how much of that substance is viable cells that can make a person sick.

The CV staining results show that only 3 coatings provide statistically lower biomass accumulation: Dursan, Ni-P-PTFE, and CrN. 

CV staining results of all 18 samples. The symbols over the coated samples symbolize statistical difference (P-values) for each result.  **: P<0.001 or significantly different from the uncoated control, *: 0.001<P<0.05 or statistically different from the control, and∇: P>0.05 or not statistically different from the control. 

The results of the viable cell counts from each surface showed that, regardless of the surface topography, Dursan is the only coating that is able to decrease active cells from the surface.  Results showed up to a 4 order of magnitude reduction in viable cell count.  

Measurement of active listeria cells on the surface of various coupons. The indicators over the bars are the same as they were for Figure 2 where ** shows a significant statistical difference from the control, * shows statistical difference, and ∇ shows essentially no statistical difference.

*  "Listeria monocytogenes biofilm formation as affected by stainless steel surface topography and coating composition"; TingtingGua; ApisakMeesrisoma; YaguangLuob; Quynh N.Dinha; SophiaLina; ManyunYang; ArnavSharma; RuoguTang; JindeZhang; ZhenJia; Patricia D.Millner; Arne J.Pearlstein; BoceZhang: Food Control, Volume 130, December 2021, 108275

Adsorption of reactive compounds in sampling and calibration systems can cost labs time and money.  A slow responding analytical system can complicate and delay troubleshooting of flow paths and gas delivery systems, causing major productivity loss and jeopardizing plant regulatory compliance.  Inert coatings, like SilcoNert^®, eliminate adsorption and give the analyst virtually real-time results. 

Comparing deactivation technologies demonstrate the benefit of an inert coating for the prevention of breakdown of reactive organochlorides.  The comparison below shows the Dursan coated flow path causes the least amount of breakdown of reactive analytes compared to common deactivation technologies.  This assures all the sample reaches the detector and achieves the highest quality test results.

Solve Missing Peak and Peak Tailing Problems

A SilcoNert® coated flow path will reduce signal loss, peak tailing and chemical adsorption while improving peak separation, sensitivity and baseline quality.  A reactive sampling flow path and GC column can result in peak distortion, lost peaks and overall poor chromatography (as seen in the example below left).  A truly inert flow path will dramatically improve chromatography quality.  SilcoNert coated GC surfaces prevent lost peaks and improve peak quality (as seen on the right chromatograph).  

An inert, non-stick, nontoxic, high durability coating like Dursan® prevents protein binding, corrosion and biofouling in sampling flow paths.  A study by Abbott Laboratories in Applied Surface Science demonstrate the bio-inertness performance and corrosion resistance of Dursan.  

Comparative QCMD (quartz crystal microbalance  with dissipation monitoring) characterization of the Dursan coating shows, when used with a non ionic surfactant rinse, a significant reduction in protein surface retention can be realized, preventing carryover and cross contamination.  The graph below shows the Dursan surface (top line) returns to baseline weight after contact with the test protein analyte.  The bottom line shows the stainless steel surface retaining the protein sample and not returning to baseline weight; indicating retention of protein.  Read the entire paper here.

Precise detection of trace compounds in fragrances or odorants require surfaces that minimize adsorption and contamination by the analyte flow path.  Olfactory detection and analytical systems must clearly and repeatably detect trace compounds in the part-per-billion range.  In order to achieve reliable ultra low level detection the flow path surface must allow all the sample to reach the LC, GC or GC-MS detector.  

Comparing a prepared, known sample concentration in coated and uncoated HPLC systems.  The first chromatogram shows the result when testing with a stainless steel frit and stainless steel column in the flow path.  There is very little signal response, indicating flow path adsorption and loss of sample.  This makes precise trace detection of target compounds difficult. 

The next chromatogram shows results using a Dursan® coated frit and column.  The peak is much larger and shows minimum tailing or distortion.  This indicates that all the sample is reaching the column and detector without flow path adsorption.  Making consistent detection of trace compounds for fragrance analysis or odor detection possible.   

The other chromatograms at the right show how the same sample peak can be distorted when even part of the flow path is reactive. 

Trace VOC Detection

Odor detection and fragrance analysis often relies on the sample system's ability to detect airborne volatile organic compounds (VOCs). Trace VOC analysis can be improved by using SilcoNert coated stainless steel. 

Testing by Mr. Stefan (S.T.) Persijn of VSL, Dutch Meterlogical Society, (in conjunction with the German Meterological Office, DWD) presented a comparative study of adsorptive properties of various materials commonly used in VOC analysis.*

Read The VOC Presentation

The study exposed various tube surfaces to methanol at 50 and 100°C and measured adsorption rate of the surfaces.  Results show that an inert coating like SilcoNert^® (called by the trade name Sulfinert® in the study) coated stainless steel prevented adsorption and reaction with VOCs in critical flow paths.  The study summary, below, highlights the comparative results:**

The VOC team then compared 10 meter lengths of SilcoNert 2000 coated and uncoated stainless steel tubing (below).  The team passed a 180 umol/mol methanol mixture through a bypass (grey areas), then switched to the test tubing.  They measured the time to achieve baseline concentration for each tube.  The SilcoNert coated tube took less than a minute to stabilize (graph B) compared to over 40 minutes for the stainless steel tube (graph A).  The comparison demonstrates the severe adsorption of trace methanol on stainless steel flow path surfaces and highlights potential delays in response that can lead to significant data reliability issues when conducting trace VOC analysis.** 

Improve Test Quality and Corrosion Resistance

Chemical exposure to solutions, such as, organic solvents, deionized water, acids or bleach, can cause a significant amount of metal ions to dissolve into the liquid, causing product contamination, system corrosion, and test problems in analytical and high purity processes. 

SilcoTek® offers CVD coating solutions to make your process, analytical, and sampling systems perform better.  Our chemically inert coatings improve test accuracy and reliability by preventing metal contamination from metal ion leaching caused by chemical reactions between the product and flow path surface.  The summary below demonstrates how metal ions can be readily leached into flow path solutions and how coated surfaces (right column, green) prevent contamination under all conditions tested.  

SilcoTek's CVD silicon coating process bonds inert, non-reactive coatings like Dursan®, Silcolloy®, and SilcoNert® to the surface.  The chemically inert coatings prevent interaction of the sample with the reactive flow path surface. 

Corrosion Resistance

Aggressive cleaning fluids, like bleach, can corrode stainless steel flow path surfaces.  Non-reactive SilcoTek coatings like Silcolloy and Dursan substantially improve the corrosion resistance of stainless steel and other alloys, prolonging usable device lifetime while maintaining sanitation.  

• Enhancing the Reliability and Accuracy of Analytical Instruments

• Adsorption and Desorption Effects in Sample Mass Transport Systems

• Use of Inert CVD Coating for Protein, Corrosion, and Moisture Resistance in Bioanalysis Applications

• Technical Insight: Protein Resistant Properties of Dursan

• Technical Insight: Dursan Process Achieves USP Class VI Certification

• Presentation: Inert CVD Coatings for Analytical Applications

• Webinar: How to Improve LC and GC With SilcoTek's Inert Coatings

• LC GC Webinar Slides, Metal Free HPLC

• Application Note: Improving Chromatography with a SilcoNert Treated Sample Flow Path

• Application Note: Bio-Inert Coatings and Liquid Chromatography
  

• Dursan^® Data Sheet

• SilcoNert® Data Sheet

 Watch our GC inertness video to see how our coating technology improves performance.

If you have a technical question about how our coating technologies will perform in your application, contact our Technical Service Team and ask the experts.

If you would like to buy a coated product directly from the manufacturer, go to our Buy Coated Products page.

To get the most out of your HPLC and GC and sampling system, coat all reactive sample flow path components and systems.  This includes:

Calibration and spec gas delivery systems

• Gas regulators
• Tubing
• Valves
• Vials

GC components

• Liners, injection ports, and weldments
• Detectors & FID jets
• GC columns
• Ampules and needles
• Transfer tubing
• Valves and fittings
• Separators and filters

HPLC Components

• Columns
• Stainless steel tubing
• Pumps
• Fittings
• Valves

Now labs have the option to improve the analytical performance of virtually the entire sampling and test flow path.   

Want to test our coating before you buy?  Get a free test coupon or arrange for a free test evaluation.