Hydrogen Peroxide Levels in Freshly Brewed Coffee and the Effects of Storage

Abstract

One of the world's most consumed beverages, coffee has its origins as early as the 15th century Ethiopia. Although there are studies on caffeine and other components of coffee such as cafestol and kahweol, up until recently knowledge of the presence of hydrogen peroxide (H2O2) in coffee was confined to the scientific community and some informed public. It is a general belief that H2O2 is formed only after long periods of storage or with certain roasting practices. The present study is focused on dispelling the myths of H2O2 in coffee. We first measured H2O2 in freshly brewed coffee from different companies using the ferrous oxidation-xylenol orange binding (FOX) assay. Following this, we examined the time-dependent accumulation of H2O2 and its changes with temperature. Further, H2O2 was estimated in coffee obtained from several local vendors. Contrary to the general belief that the accumulation of H2O2 is an aging phenomenon of coffee, we found this toxicant even in freshly brewed coffee. This was true for all brands tested, and the H2O2 content increased upon storage. The highest increase was seen in coffee stored on the hot plate compared to the ones kept at room temperature (22-25 °C) or in the cold (0-4 °C).The H2O2 content of coffee from different vendors ranged between 0.29 and 0.82 mM, which is 5- to 20-fold higher than the typical H2O2 concentrations at which significant cytotoxic effects have been reported for assay systems using the human Fanconi deficient (PD20 FANCD2−/−) fibroblasts and other cell types. Our findings are deemed to shine new light on the probable toxic effects of a commonly consumed beverage like coffee, and the time and temperature dependent variations of keeping. While there are documented benefits of consumption of coffee, the possible H2O2-medicated toxic effects are critical and should be considered. Future studies are warranted to delineate the contribution of H2O2 in the healthy wellbeing of individuals who consume coffee extensively.