Coffee is a popular and well-known beverage that is made from the seeds inside the fruit grown on coffee trees. To produce a cup of coffee, the seeds undergo a lengthy and complex processing procedure. Different processing styles have evolved as a response to environmental, resource-dependent or market needs, and they involve the use of fermentation.

Fermentation is a metabolic process performed by organisms seeking fuel, and it is the most important factor affecting a food product’s flavour. During the coffee production process, the mucilage that surrounds the seeds is removed, and this inevitably exposes the seeds to oxygen. The presence of oxygen favours the growth of microorganisms, and the microorganisms consume the sugars in the mucilage, producing volatile organic compounds.

These volatile organic compounds are the main source of flavourings used in tea and coffee. However, they also react with water to form chlorinated chemicals known as disinfection byproducts (DBPs). The levels of DBPs in tea and coffee mainly depend on the amount of water used for preparation. In this study, we compared the levels of DBPs in instant coffee and in tea made with the same volume of water. The results showed that instant coffee contains significantly lower amounts of DBPs than tea, and that the differences are primarily due to the type of water used for brewing.

The level of free bioactive amines in coffee is affected by various factors, such as the beans’ characteristics and the processing steps. The levels of amines in the coffee we tested varied, with tryptamine and putrescine being more prevalent in green coffee beans, and phenylethylamine being more prominent in ground and roasted beans. The levels of ochratoxin A were lower in roasted and ground beans, but higher in instant coffee samples.

In this study, we investigated the contents of cadmium (Cd) and lead (Pb) in 49 samples of instant coffee, coffee drinks and coffee substitutes purchased in stores in Chelm, Zamosc and Lublin (eastern Poland). The levels of these heavy metals were determined by ICP analysis. The safety of consuming these beverages by adult Poles was estimated using the tolerable weekly intake (TWI), benchmark dose lower confidence limit, chronic daily intake (CDI) and target hazard quotient (THQ). It was found that drinking up to three servings of roasted and instant coffee per day does not result in excessive dietary exposure to Cd and Pb.