The elephant in the room.

Cold brew production involves the use of water and coffee grounds over an extended period without heat treatment. This environment is conducive to the growth of various microorganisms, including bacteria, yeast, and molds.

The main concern is the growth of following bacteria:?

• Escherichia coli,?
• Enterobacteriaceae (including Salmonella),
• coagulase-positive Staphylococcus aureus,
• Listeria monocytogenes (Listeria)

Some bacteria, particularly acid-tolerant strains, can still survive and even proliferate in mildly acidic conditions. This includes certain pathogens that might cause foodborne illnesses. Moreover, the acidity might not be sufficient to inhibit the growth of all spoilage microorganisms, such as molds and yeasts.

Hard Beans Study at the University of Opole

The aim of the study back in 2018 was to determine, based on microbiological criteria, the suitability for consumption of cold brew coffee using the traditional 24-hour method.

The scope of the research was to assess the microbiological condition of cold macerated coffee and to define guidelines for microbiological safety.

The research was lead by Professor Agnieszka Dolhańczuk-?ródka Director of the Institute of Biotechnology at the University of Opole.

During one of the studies, we’ve conducted the coffee samples delivered to the laboratory in washed, but not sterilized KEGs were significantly contaminated.

Immediately after extraction, the samples contained:

• 690 CFU/ml - total mesophilic bacterial count.
• 27 CFU/ml - mold count.

Samples were kept in temp. range of 5 - 25C.

After 2 days of storage at 15°C, the bacterial count increased to:

• 150 000 CFU/ml.

The European Union standards allow cold brew CFU/ml values to be no higher than 100 000/ml*.

Results show that the only proper condition for unpasteurized cold brew brewing and storage is below 5C. Regardless of the temperature and storage time, the cold brew samples showed the presence of: Enterobacteriaceae and Escherichia coli bacteria which most probably came from the washed (using common coffee cleaning agents) but not sterilized KEGs.

*EU microbiological criteria for cold beverages:

• Total Viable Count (TVC): < 100,000 CFU/ml
• Yeasts and Molds: < 100 CFU/ml
• Coliforms: < 1 CFU/ml or non-detectable
• E. coli: Non-detectable in 25 ml
• Salmonella: Non-detectable in 25 ml
• Listeria monocytogenes: Non-detectable in 25 ml

Regulation (EC) No 1441/2007, in conjunction with Regulation (EC) No 2073/2005

New technologies, such as the Hardtank system, provide a solution to these microbial challenges by producing cold brew coffee in less than one hour. This rapid brewing method significantly reduces the time coffee grounds are exposed to water and oxygen, minimizing the opportunity for microbial growth and ensuring a safer product. The Hardtank system also includes built-in cleaning and sanitation programs that improve safety by making sure all equipment is thoroughly cleaned and sanitized between production days.

However, the main challenge remains in staff training and education, implementing safety protocols, and standardizing procedures to maintain these high safety standards. Properly trained staff and adherence to strict safety protocols are crucial for using these technologies effectively and consistently producing safe, high-quality cold brew coffee.