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Should We Reconsider Espresso Machine Descaling/Cleaning (Part 1)

Measuring the potential lead contamination in the espresso machines

Many are asking me how I came up with ideas for the projects I’m working on or experimenting with. And I have to say that in most cases it is just spontaneous ideas that are emerging during article reading, video watching, or conversation. The next experiment is also influenced by a post from Barista Hustle. In their article “Wheels of Steel” they mentioned possible lead contamination coming from old brass or copper boiler, tubing, and parts, and I started researching more deeply.


In the past, there were little researches on this topic. In the year 2014, the German Federal Institute for Risk Assessment came into the conclusion that there could be a possible risk of lead leaching in the water after espresso machine descaling (1).

High levels of lead were measured right after descaling,

but the whole report is more of a guideline than thorough research. BfR is suggesting that the EU must control the materials in contact with water and must use recommended limits for lead in the water of 10ppb (parts per billion) for coffee beverages. In the mentioned study several different espresso machines were analyzed. All of them were small domestic or capsule espresso machines. No professional espresso machines were analyzed. The research I conducted aims to analyze water from professional equipment for two reasons. First, in cheap domestic espresso machines, most of the parts in contact with water are made from plastic or stainless steel, while the potential lead contamination could come from brass or copper parts used in the professional ones. The second reason is that rarely someone with a very cheap machine will put the effort into cleaning the boiler or flow paths. On the other hand, descaling is performed regularly in most coffee shops, especially those focused on coffee quality. I aim to research only professional espresso machines.


The second research on this topic was made in the year 2015 by the Ministry of Environment and Food of Denmark (2). The goal of this project was to estimate the intake of lead from coffee in the Danish population and to assess the amount contributed from coffee, water, and coffee brewers, respectively. In total 44 coffee bean products and 7 instant coffee products were analyzed. The analysis indicated that the content of lead in the 44 samples of coffee beans was ranging from 4.5 to 65.3 ppb with an average of 15.9 ppb. The main purpose of this research was a little different from what I was planning to do. It wasn’t about to find the source of contamination, but it only suggested that contamination could be a result of descaling.


And before you rush into a panic, I have to say that there is nothing to worry about.

In both types of research, the concentration of lead is reasonably low. Someone could say that there is no safe lead concentration but comparing it with legislation limits for a wine of 200ppb by the Commission Regulation (EC) No 1881/2006 of 19 December 2006, the levels found in coffee are lower. Still, this is a concern that should be regulated and monitored for better safety.


My project aims to compare three different scenarios related to professional espresso machines. It is not about the lead coming from the coffee as this is a topic for another research in the future. In high interest are old espresso machines produced before implementing few manufacturing improvements like lowering lead content in brass below 0.25% or coated brass.


  1. Compare the concentration of lead in water from the heat exchanger/brewing boiler or directly from the steam boiler.

  2. Compare the concentration of lead in water before and after the descaling/cleaning procedure.

  3. Compare the concentration of lead in water after several cycles of purging with water after descaling/cleaning.


Results from this research will give me a possible answer to the questions below:


  1. Where is the contamination coming from?

  2. Is it necessary to change our descaling/cleaning procedures?


For this experiment, I collected water samples for all the mentioned scenarios and kept them in lead-free containers in a refrigerator until analysis.

I used an ICP-OES instrument for quantitation of the lead concentration in all water samples.

Inductively coupled plasma atomic emission spectroscopy (ICP-AES), also referred to as inductively coupled plasma optical emission spectrometry (ICP-OES), is an analytical technique used for the detection of chemical elements (3). Argon gas is used to create the plasma. An intense electromagnetic field is created within the coil by the high-power radiofrequency. The argon is ignited with a Tesla unit that creates a discharge arc trough the argon flow to initiate the ionization process. The argon gas is ionized in the intense electromagnetic field. A stable, high-temperature plasma of about 7000-10000 K is then generated as the result of the inelastic collisions created between the neutral argon atoms and the charged particles.

An aqueous or organic sample is pulverized and introduced inside the plasma flame. The sample immediately collides with the electrons and charged ions in the plasma and is itself broken down into charged ions. The various molecules break up into their respective atoms which then lose electrons and recombine repeatedly in the plasma, giving off radiation at the characteristic wavelengths of the elements involved.


Within the optical unit, after the light is separated into its different wavelengths (colors), the light intensity is measured by an array of semiconductor photodetectors such as charge-coupled devices (CCDs). ICP-OES is widely used for quantitation of trace elements and heavy metals like lead in concentration levels of 1-10ppb or lower.


To create a calibration, I took a lead standard as Certified reference material (CRMs) with a concentration of 1000ppm and diluted it in series creating a calibration curve for the lead with concentrations of 1ppb, 5ppb, 10ppb, 20ppb, 50ppb, and 200ppb. The correlation coefficient of the calibration curve was 1.000, meaning that I got perfect linearity and reproducibility.

Note! I’m not claiming for a comprehensive or representative sample collection for this analysis. This is because of the limited number of analyzed samples and some espresso machine unknown history.

First, I measured water samples collected from the heat exchanger or brew boiler and compared them with the water from a steam boiler.


You can continue reading the entire article on my Patreon page HERE or visit www.patreon.com/npcoffeescience. There you can find results for lead concentration for the measured water samples. Thank you!



(1) Freisetzung von Blei aus Kaffee- und Espressomaschinen, Aktualisierte Stellungnahme Nr. 003/2014 des BfR vom 14. Januar 2014*

(2) Exposure to lead from intake of coffee, The Danish Environmental Protection Agency, Environmental project No. 1785, 2015.

(3)https://en.wikipedia.org/wiki/Inductively_coupled_plasma_atomic_emission_spectroscopy


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