The impact of spent coffee grounds on carotenoid and chlorophyll content in
lettuce (Lactuca sativa L. var. capitata) was evaluated. A greenhouse pot experiment was
conducted with spent coffee amounts ranging from 0% to 20% (v/v). All evaluated
pigments increased proportionally to spent coffee amounts. Lutein and β-carotene levels
increased up to 90% and 72%, respectively, while chlorophylls increased up to 61%.
Biomass was also improved in the presence of 2.5% to 10% spent coffee, decreasing for
higher amounts. Nevertheless, all plants were characterized by lower organic nitrogen
content than the control ones, inversely to the spent coffee amounts, pointing to possible
induced stress. Collected data suggests that plants nutritional features, with regards to these
bioactive compounds, can be improved by the presence of low amounts of spent coffee
grounds (up to 10%). This observation is particularly important because soil amendment
with spent coffee grounds is becoming increasingly common within domestic agriculture.
Still, further studies on the detailed influence of spent coffee bioactive compounds are
mandatory, particularly regarding caffeine.
