University of Arkansas, Fayetteville Division of Agriculture


Grape pomace, a by-product of juice and wine processing, is a rich source of anthocyanins, antioxidant compounds that may afford protection against cancer and coronary heart disease. Unfortunately, traditional extraction of these antioxidants involves use of organic solvents, which pose serious safety and disposal problems for industry. Clearly a need exists for “green” extraction technologies—such as use of subcritical water—that eliminate or reduce the amount of organic solvents. In this study, we determined the efficacy of subcritical and carbonated water in extraction of anthocyanins from red grape pomace. Extraction variables including particle size, pomace mass, and temperature were optimized, and results were compared with those obtained using a traditional solvent-extraction method. According to the total anthocyanin assay, optimum conditions for extraction consisted of the smaller particle size (400 µm) and temperature of 100°C. Under these conditions, subcritical water and carbonated water extracted about 70% of anthocyanins obtained using the traditional organic solvent method. The highest antioxidant-capacity value measured by the ORAC assay was obtained at 140°C, suggesting that Maillard browning products were produced when grape pomace was exposed to increasing temperatures. Subcritical water appears to be a promising, environmentally benign technology to recover health-promoting compounds from grape-processing waste.