The effect of organic farming on total phenols, total flavonoids, brown compounds and antioxidant activity of spent coffee grounds from Mexico

ABSTRACT Mexico is one of the world leaders in the production of coffee, but research on bioactive compounds and antioxidant activity in Mexican coffee has been extremely limited and, importantly, the effect of organic farming on these properties has not been widely studied. Spent coffee grounds (SCG), the main by-product of coffee brewing, represent a serious environmental problem, but could become an important source of bioactive compounds for the pharmaceutical and food-processing industry. The aim of this work was, therefore, to study the effect of organic farming on bioactive and antioxidant properties of SCG; comparing samples of organic and conventionally grown coffee from the Mexican states of Veracruz and Chiapas, both of which produce coffee with the ‘Protected Designation of Origin’ distinction. Concentrations of total phenolic compound and total flavonoid compounds, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis-3-ethylbenzthiazoline 6- sulphonic-acid) antioxidant activity, and brown compound concentration were determined in SCG. Repeated measures ANOVAs were carried out on the data. Organic SCG samples showed significantly higher bioactive compound concentration (p < 0.01) and antioxidant activity (p < 0.001) than conventional SCG samples. This difference held across various extractions and the two geographical locations. Thus, this Mexican organic coffee by-product may represent an interesting source of such compounds for diverse industrial applications. Given that Mexico is one of the top producers of organic coffee in the world, there is a need for further research to consider other important variables, such as the type of coffee processing by-product and the type of coffee extraction process.