Application of persimmon (Diospyros kaki L.) peel extract in indigo dyeing as an eco-friendly alternative reductant

The aim of this study is to investigate the efficacy of persimmon ( Diospyros kaki L.) peel extract as a reductant for indigo dyeing. Dried persimmon peel was water extracted and its sugar contents and functionalities were determined. Its reducing power was studied in terms of redox potential of the indigo bath and color strength (K/S value) of the ramie fabrics dyed in the indigo reduction bath. Total sugar content of the extract was 74.3%. Antioxidant capacity reached up to 86.0% at 3.5 μg/mL of the extract concentration. The persimmon peel extract had an effect on indigo reduction and the maximum color strength was obtained within one or two day. At 2–3% of the extract concentration, the redox potential of the indigo bath was maintained in the range of − 550 ~ − 600 mV for 10 days. With increase in the extract concentration, reduction state lasted for longer time and higher color strength was obtained. The persimmon peel extract can be used for indigo reduction dyeing as a sustainable, nontoxic, biodegradable alternative to sodium dithionite.