Cold Brew Controversy: Balancing Flavor and Food Safety (pt. 1/3)

Cold brewing methods can be found in various coffee cultures throughout history. One notable predecessor is the Japanese method known as "Kyoto-style" coffee, which emerged in the 17th century. This method involved brewing coffee with cold water over an extended period, often using intricate glass towers that allowed for a slow, drip-style extraction.

In the United States, the concept of cold brew coffee has roots in the 1960s when it was popularized by a chemical engineering graduate named Todd Simpson. His invention marked the beginning of a modern resurgence in cold brew coffee.

Today, cold brew has become more than just a trend, it's a flavorful and versatile coffee preparation method embraced by coffee shops, cafes, and enthusiasts around the world.

Regarding novel technologies, innovations in cold brew typically revolve around brewing equipment, packaging, and distribution. Some companies were exploring more efficient and scalable methods of producing cold brew, while others were focusing on extending the shelf life of cold brew products, particularly RTD options. Additionally, there were advancements in sustainable packaging materials and nitrogen infusion technologies for nitro cold brew.

Microbial risks?

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. Contaminants can come from the coffee beans, equipment, and the production environment. Without proper controls, these microorganisms can proliferate and pose health risks to consumers. The main concern is the growth of following bacteria:?

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

Yeast and molds are also capable of growth in cold brew environments. While not all molds and yeasts are harmful, some can produce mycotoxins, which pose health risks.?

Mycotoxins are toxic compounds produced by certain types of molds (fungi) that can grow on various crops, including grains, nuts, and coffee beans. These toxins pose a significant health risk to humans and animals when ingested, inhaled, or otherwise exposed to them. It's worth noting that mycotoxin contamination in coffee is relatively rare and is typically addressed through quality control measures in coffee production and processing. During a three-year long study on green and roasted coffee we’ve measured both Aflatoxins and Ochratoxin A. Twain were below the permitted level throughout the time.??

Mildly acidic environment?

Cold brew coffee is brewed using cold or room temperature water over an extended period (depending on the brewing method from 1 hour e.g. Hardtank to 24 hours e.g. traditional way). This method also creates an environment with certain characteristics that can potentially encourage microbial growth during extraction and storage.?

One critical aspect is cold brew's mildly acidic environment. While coffee is generally considered acidic, cold brew typically has a pH ranging from 4,85 to 5,10 based on a study published in Scientific Reports by Nature by Niny Z. Rao of Thomas Jefferson University. While this pH range is not highly conducive to the growth of many harmful bacteria, it's important to note that not all microorganisms are equally affected by acidity.

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.

The potential for microbial growth is compounded by the nature of the cold brew extraction process. Because cold brew coffee is made using cold water and steeped for an extended time, there's a possibility that microorganisms present on the coffee grounds or in the water can multiply over this duration. This is particularly true if the equipment used for brewing, such as containers or filters, is not properly sanitized.?

During one of the studies we’ve conducted at Hard Beans with the Institute of Biotechnology of the University of Opole the coffee samples delivered to the laboratory in washed using popular cold brew cleaning agent , but not sterilized KEGs were significantly contaminated. Immediately after maceration, the samples contained a total mesophilic bacterial count of 690 CFU/ml and mold count of 27 CFU/ml. After 24 hours of storage at temperatures ranging from 5°C to 25°C, the bacterial count increased to approximately 1.70 × 10^2 CFU/ml. Regardless of the temperature and storage time, the cold brew samples showed the presence of Enterobacteriaceae and Escherichia coli bacteria. No presence of Salmonella or Staphylococcus aureus bacteria was detected. Therefore, it is recommended to develop procedures for cleaning and disinfection relating to specific production cycles. In coffee samples delivered to the laboratory immediately after maceration in sterile bottles, the bacterial count was 324 CFU/ml, but no presence of fungi. In the samples kept at 5°C, the number of mesophilic bacteria increased to 3.90 × 10^4 CFU/ml, and fungi to 1.00 × 10^2 CFU/ml within 7 days. The microflora of coffee samples kept at 25°C was dominated by yeast. Their number after 5 days was 3.20 × 10^5 CFU/ml. These samples contained yeasts of the genus Rhodotorula and the mold Penicillium crustosum. The presence of Enterobacteriaceae, Salmonella, Escherichia coli and Staphylococcus aureus bacteria was not detected in coffee samples in sterile bottles.

Furthermore, during storage, the cold brew should be kept at refrigerated temperatures (typically below 5°C or 41°F). While refrigeration slows down microbial growth, it doesn't completely halt it, especially if the cold brew wasn't brewed and handled under strict hygiene conditions.

In summary, while the mildly acidic environment of cold brew does inhibit the growth of many microorganisms, it's not foolproof. Some acid-tolerant pathogens and spoilage microorganisms can still survive and multiply. Proper hygiene practices throughout the brewing and storage process are essential to minimize the risk of microbial contamination and ensure the safety of the cold brew.

Update: Part 2