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J. Cosmet. Sci., 70, 313–325 (November/December 2019) 313 Utilization of Coffee Silverskin By-Product from Coffee Roasting Industry through Extraction Process for the Development of Antioxidant Skin Gel SAMUEL P. KUSUMOCAHYO, PATRICK TANGGUH, CHRISTINA D. ANNELIES, and HERY SUTANTO , Department of Chemical Engineering, Faculty of Life Sciences & Technology, Swiss German University, Tangerang 15143, Indonesia (S.P.K., P.T., C.D.A., H.S.) Accepted for publication October 4, 2019. Synopsis Coffee roasting industries generate a by-product called coffee silverskin that is usually disposed of as waste. The valorization of this abundant waste is necessary because of the antioxidant compounds in coffee silverskin. In this study, coffee silverskin was extracted in different extraction conditions to obtain an extract with high antioxidant activity and to use it as an additive for antioxidant skin gel. The extracts were characterized for the total phenolic content by using the Folin–Ciocalteu method. The antioxidant activity was determined by using the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay. It was found that the extraction time and temperature strongly affected the total phenolic content and the antioxidant activity of the extracts. The extraction at 40°C and 60 min resulted in an extract with a high total phenolic content of 31.15 ± 2.77 mg Gallic Acid Equivalent/g coffee silverskin and a high antioxidant activity of 68.44 ± 0.76%. The extract solution was spray-dried to produce extract powder, which was then added to a basic skin gel with different extract concentrations. It was observed that the antioxidant activity of the gel increased with increasing extract concentration in the gel. This result showed that coffee silverskin has great potential as a source of antioxidants for various skin care products. IN TRODUCTION Anti oxidants are very important for the human body because they protect the human body against reactive oxygen species, known as free radicals, which can cause oxidative reac- tions in human cells. Although the human body has an internal defense system toward free radicals (1), it still requires the intake of antioxidants from outside that usually can be obtained from synthetic or natural products, such as fruits and vegetables, containing antioxidants (2). Recently, the interest in natural products for healthy foods, beverages, supplements, and health care products has been rising along with the increasing aware- ness of a healthy life style (3–5). Address all correspondence to Samuel P. Kusumocahyo at samuel.kusumocahyo@sgu.ac.id.