Utilization of Coffee Silverskin By-Product from Coffee Roasting Industry through Extraction Process for the Development of Antioxidant Skin Gel.

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.

Solubility and Antioxidant Potential of a Pyrogallol Derivative for Biodiesel Additive.

Biodiesel is a renewable plant-based fuel as an alternative for fossil diesel fuel which has many advantages. However, its high content of unsaturated fatty acid causes an oxidation instability during storage. Numerous additives have been used and developed to overcome this problem such as the application of phenolic compound-based antioxidants. Pyrogallol is reported to be one of the best phenolic antioxidants for biodiesel. Unfortunately, pyrogallol has a low solubility in oil solution. In this research, pyrogallol solubility is increased by preparing a pyrogallol derivative through a reaction between pyrogallol and methyl linoleate in the presence of radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The spectrophotometric method was used for solubility test. Antioxidant potential was examined using acid value determination during a four-week storage period as well as the Rancimat test to see its performance under accelerated oxidation conditions. The reaction produced a molecule which has a molecular weight of 418 g/mol, representing pyrogallol derivative which has a new C-O covalent bond with methyl linoleate. The result was confirmed by using nuclear magnetic resonance (1H-NMR, 13C-NMR, and 2D-HMQC) resulting in a molecular structure of methyl (10E,12E)-9-(2,6-dihydroxyphenoxy)octadeca-10,12-dienoate and its isomer methyl (9E,11E)-13-(2,6-dihydroxyphenoxy)octadeca-9,11-dienoate with a yield of 12.86% and selectivity of 21.05% on the basis of pyrogallol. Compared to pyrogallol, tert-butylhydroquinone (TBHQ), and gallic acid, the pyrogallol derivative has the highest solubility and acid value stability in palm oil biodiesel. The Rancimat induction time (IP) result of the pyrogallol derivative is higher than the biodiesel and is above the accelerated oxidation test American Society for Testing and Materials (ASTM) D 6751 standard.