Coffee: caffeine content and antioxidant activity at different stages of extraction

The aim of the study is to investigate the dynamics of caffeine extraction and antioxidant activity during coffee extraction in the food industry. Coffee extraction was performed with water in 4 stages of 100 ml in a capsule coffee machine, and at each stage, soluble dry substances (SDS) were determined in the extracts by refractometry, caffeine content by spectrophotometry, and antioxidant activity (AOA) on an Expert-006-antioxidants coulometer. Two types of coffee were used for extraction: Arabica and Robusta. Extracts obtained from 7 g of coffee of different types and names differed in the content of SDS, caffeine, and AOA, but their dynamics during extraction were similar. The extracts obtained at stage I were characterrized by the maximum amount of RSV (0.84-1.64 %) and AOA (287.76-327.38 mg rutin/100 ml), which constituted 67-70 % of the total values for all stages of extraction and quantitatively predominated in robusta coffee. Further extraction reduced the AOA of the extracts, but the greatest changes occurred at stage III, decreasing the AOA of the coffee extracts by 8-10 times compared to the previous stage. The dynamics of caffeine content in extracts at different stages of extraction differed from AOA. Extracts obtained at stages I and II had comparable amounts of caffeine, statistically significant differences were found only in robusta coffee extracts. At stage III of extraction, the caffeine content decreased more than 2 times. Extracts obtained at stage II from already used coffee (coffee grounds) contain caffeine and antioxidants, which will allow them to be used for the production of food products with specified properties.