Detection and formation of fluorescent carbon nanodots in coffee brews and its relationship with other compositions

Abstract

Coffee, a widely consumed beverage, offers health benefits alongside enjoyment. While coffee chemistry has been studied for years, the existence and formation of nanoparticles in coffee remain incompletely understood. This research explores how carbon nanodots (C-CNDs) form in coffee under various conditions of brewing, including (1) bean types, (2) grind sizes, (3) the coffee-to-water ratios, and (4) brewing time and temperatures. The results show that the C-CNDs formation increased with Arabica beans, coaster grinds, and a 1:15 coffee-to-water ratio (g/g). Higher temperatures (over 90 oC) and longer brewing times also yielded more C-CNDs. Our findings revealed that the isolated C-CNDs have an average size of 3.2 ± 0.9 nm and are characterized using fluorescence spectrophotometer, UV-Vis, and TEM techniques. We also examined fundamental coffee compositions like caffeine content, pH, total dissolved solids (TDS), and browning color, finding the correlation with C-CNDs. While C-CNDs show a strong negative correlation with caffeine content (-0.8), there is a weak negative correlation with pH (-0.33), TDS (-0.48), and browning color (-0.62). This establishes a new link between C-CNDs and caffeine content. These discoveries, backed by robust scientific methods, enhance our understanding of coffee's composition and have potential health implications.