Citric Acid (write-in)

[Alistair Durie]

From: Josh Longsdorf
Ritual Coffee Roasters, Napa, Ca

Recently while back flushing our machine and scrubbing out our portafilters to soak I realized I had earlier seen citric acid at the spice vendor next door to us at the market. Thinking back to high school chemistry I remembered that citric acid is sometimes used as a benign cleaner but also happens to be natural so I decided to clean two portafilters and group heads with our good ol' standard industry cleaner and the other two with citric acid. The results using the same ratios were awesome. Not only were the portafilters shinier from the citric acid but it seemed to have worked on the group heads as well. I know that citric acid can be used in descaling boilers but was wondering if anyone knew of any adverse effects that continued use of the citric acid may cause to the machine or if anyone else out there has experimented with natural cleaners for their machines.

[stormer]

It's my understanding that citric acid is what makes fizzy cleaners fizzy, at least in the case of cleaner tablets.

Josh LongsdorfI decided to clean two portafilters and group heads with our good ol' standard industry cleaner and the other two with citric acid.

Were the latter two cleaned with citric acid or with a cleaner/citric acid mixture?

[Luke Shaffer]

We still cafiza the hell out of our Synessos and then rinse them like crazy, but I know that Cleancaf is supposed to be a citric acid based cleaner that can be used on both coffee brewers and espresso machines. Both espressoparts and sweetmarias indicate that it can be used for use on espresso machines. I don't think it would be an issue... but I hate to be the guinea pig. I'd probably shoot an email to my equipment manufacturer and see what they think first...

[manderson]

From our Chemist here at Cirqua Phil Wagner;

Citric acid is a good cleaner and a slight reducing agent. A reducing agent will turn rust, to some degree, back into soluble iron so any iron deposits will get clearer if not disappear. However, every one here is talking about scale and usually that is associated with calcium carbonate and that is OK until the scale turns out to be calcium sulfate then all bets are off. Calcium sulfate is "gypsum". In steam boilers it will precipitate out and make some serious crystals in the boiler. Calcium sulfate precipitation is based solely on concentration or saturation, whereas, calcium carbonate precipitation is due to a chemical shift in heating and results in a loss of carbon dioxide converting calcium bicarbonate to calcium carbonate (lime). The carbonate anion is sensitive to weak acid compounds like citric acid and acetic acid (vinegar). Acid converts the carbonate back to carbon dioxide and water, while the organic anion attaches to the calcium to form calcium citrate or calcium acetate

When calcium sulfate comes into play due to the water source, it is non-acidifiable because the acid required to convert the sulfate to sulfuric acid has to be a strong acid. There are some rather complicated processes to remove gypsum scale from the metal which involves ammonia, carbon dioxide and ammonium carbonate. This ultimately will create calcium carbonate which can then be acidified with a week acid to dissolve it out.

About the only way to control the scaling process is to feed minerally balanced water into the boiler. This would be subject to a minimum scale potential due to heating and would have no sulfates to precipitate out in the solution. This should provide fairly stable water chemistry even through the heating process so that scaling is minimized.

Michael Anderson – Director of R&D – Cirqua Customized Water

[luca]

If you put citric acid into water in a jar, it will dissolve. If you pour oil onto that water, it will float as a separate layer. Presumably, if you shake the jar, the solution will emulsify and will then split. I haven't done it, but a salad dressing is basically an acid and an oil and it will split. If you add detergent to the jar and shake, it will foam up and form a single stable solution. Something in the detergent allows the oil to 'dissolve' into water. (From memory, surfactant molecules form a micelle around the oil, but I know that there are other things in the detergent as well.)

If you take a pan, put some vegetable oil in it, add ground coffee and apply some heat, it eventually starts to smell like a dirty group head (yes, I have done it). If you do a few clean water backflushes and remove the shower screen from your machine, you will probably still be able to wipe something off it.

I think that it's a fair bet that some of the stuff responsible for dirty group heads is not water soluble (hydrophobic); probably coffee oils. How is backflushing with citric acid going to remove those compounds? Wouldn't you need a detergent to do that?

[phaelon56]

If you take a pan, put some vegetable oil in it, add ground coffee and apply some heat, it eventually starts to smell like a dirty group head (yes, I have done it).

Yes I believe you... but how did it taste?