The risk of espresso coffee machines

by Jennifer Bowden / 08 April, 2016
We love our coffee, but there are ways to ensure we don’t get more from a brew than we bargained for.
The brewing method can significantly influence the quantity of compounds in your coffee. Photo/Getty Images
The brewing method can significantly influence the quantity of compounds in your coffee. Photo/Getty Images

Whether it’s a flat white, latte, long black or cappuccino, we’ve become a nation of coffee drinkers. And nowadays our taste for good coffee isn’t reserved for cafes.

Many homes have an espresso coffee machine or the more recently introduced pod- or capsule-style brew-maker. That’s all well and good, but some scientists are concerned at the potential for these machines to deliver more than coffee.

German researchers recently investigated whether metal contaminants such as lead and nickel were leaching from coffee machines into brews. They tested eight machines: three standard espresso makers, three coffee-pod and two coffee-capsule machines. All were tested for three days before and three days after decalcification.

In general, the release of contaminants decreased from the first to the last drink brewed each day, and contaminants were well below recommended levels. However, after decalcification, a big increase in metal-leaching occurred, with levels again decreasing in subsequent days.

The espresso machines were by far the worst offenders. In some cases the levels of lead, nickel, manganese, chromium and zinc leached after decalcification exceeded limits proposed by the Council of Europe for metals and alloys in contact with food. Two of the three espresso machines leached lead levels capable of prompting health concern, one of them releasing 150 times more than the recommended limit.

Given the variation in degree of contamination, the researchers point out that it should be technically possible to reduce metal leaching.

There is no specified food-safety level for lead in coffee or other beverages in this country. “Limits are only established for foods that have the potential to make a significant contribution to the total dietary exposure of a contaminant,” says a Ministry for Primary Industries (MPI) spokesperson.

MPI says there is no indication that coffee is a food-safety concern. In 2009, coffee (both instant and ground beans) was analysed in the ministry’s roughly five-yearly Total Diet Study and lead was found at “very low levels, as in other parts of the diet”. However, the ministry’s testing didn’t involve in-depth leaching analysis of the type the German researchers did.

Also of interest is the recent discovery by Spanish researchers of higher than expected mycotoxin levels in coffee. Mycotoxins are produced by common fungi found in soil, decaying vegetation, hay and grains. Some can be carcinogenic or hepatotoxic (damaging to the liver) and cause disease or even death. Aflatoxins, produced by aspergillus fungi, are an example of a mycotoxin (see “Nuts to all that”, Listener, December 12, 2015). Consequently, there are strict guidelines intended to minimise mycotoxin levels in animal and human foodstuffs.

The Spanish researchers tested 103 coffee samples, including caffeinated, decaffeinated, beans and pre-portioned capsules with and without milk powder. Mycotoxins, including ochratoxin A (OTA), were found in every coffee type, which is not unexpected. And although low levels of OTA were generally found, five samples contained amounts that exceeded maximum limits in Europe. OTA has been shown to cause kidney disease and produce tumours in the urinary tract of humans.

These results are not alarming, the researchers say, but they suggest that regularly assessing the risk coffee presents in terms of mycotoxin exposure is warranted.

The ministry runs a rolling mycotoxin surveillance programme to determine the occurrence and levels of mycotoxins in the food supply. Testing of coffee was done in 2000 by the Ministry of Health, and again in 2011 as part of MPI work, when brewed coffee made with both instant and ground coffee was analysed.

However, only 16 samples were tested, one of which had trace levels of OTA.

“Using these results and ochratoxin A results for the other foods tested, an exposure assessment was undertaken and no evidence was found to suggest that ochratoxin A in coffee currently presents a health risk to New Zea­landers,” says an MPI spokesperson. Thus, “coffee is not deemed of high regu­latory interest under the Food Act 2014 and therefore not subject to testing on import.”

There are ways to ensure we minimise our exposure to toxins, contaminants and other harmful compounds potentially lurking in our coffee. Espresso machines score a few points in this area. Spanish ­researchers found espresso makers cut OTA levels by nearly half, compared with a third by moka brewing and just 14.5% by the auto-drip method.

Brewing method can also significantly influence the quantity of two other coffee compounds, cafestol and kahweol. Research suggests cafestol, and to a lesser degree kahweol, may adversely affect blood lipid profiles and increase cardiovascular risk.

Heart Foundation national nutrition adviser Angela Berrill says traditional Scandinavian- and Turkish-style coffees, and unfiltered plunger or boiled coarse-ground brews, raise cholesterol more than filtered, percolated or instant coffee. Although espresso coffee contains more cafestol and kahweol than paper-filtered coffee, it is consumed in smaller amounts so may have little affect on lipid profiles.


  • Choose a filtered, percolated, instant or espresso coffee.

  • Regularly rinse your coffee machine, especially after decalcification.

  • Avoid mouldy coffee beans or powder.

  • Limit consumption of high-caffeine beverages to the equivalent of five cups of coffee a day.

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