Zurich Laboratory Detects Intestinal Bacteria in Coffee Machines

A recent investigation by the Zurich Cantonal Laboratory has revealed hygiene concerns in milk-based drinks dispensed from fully automatic coffee machines. The laboratory found that one in four samples tested contained excessive levels of intestinal bacteria.

The analysis, conducted last year, involved 15 samples collected from various machines located in restaurants, petrol stations, and public spaces. According to the canton’s press release, four of the samples exceeded the acceptable limits for Enterobacteria—microorganisms commonly found in the environment and in the intestines of humans and animals. Certain strains of these bacteria are known to cause gastrointestinal illnesses.

In one additional case, the machines showed elevated levels of aerobic mesophilic bacteria—a diverse group of microbes that also indicate hygiene deficiencies.

While most of these machines use pasteurized or UHT-treated milk, which is nearly sterile upon entry, the issue arises from internal contamination. Germs can thrive in milk residues that remain in the system if cleaning is neglected.

Machine operators were notified and instructed to investigate the causes and implement corrective measures. Follow-up inspections confirmed that no further hygiene limits were breached after these interventions.

This study underscores the importance of regular and thorough cleaning routines for fully automatic coffee machines, especially those that handle milk. Without proper maintenance, even advanced coffee equipment can become a breeding ground for bacteria.