No abstract

An abundant and low-cost agricultural waste such as vine shoots (Vitis vinifera) (VS), which is generated by the annual pruning of vineyards, has been used as raw material in the preparation of powder activated carbon (AC) with a view to develop a new fining agent for white wines. A commercial activated carbon, S5X-Agrovin, was used for comparison purposes. From VS size-reduced pieces, AC was prepared using phosphoric acid as activating agent. The concentration of the H(3)PO(4) solution, the impregnation temperature, and the carbonization conditions were controlled. The carbons were texturally characterized by gas adsorption (N(2), -196 degrees C), mercury porosimetry, and density measurements. FT-IR spectroscopy was used in the analysis of the surface functional groups and structures of the carbons. Three varieties of white wine (i.e., cv. Cayetana, cv. Macabeo, and cv. Sauvignon Blanc) were treated with the activated carbons. Color changes were monitored by UV-vis spectrometry. Significant differences in the degree of uptake of polyphenols were observed depending on the wine variety and on the method of preparation of activated carbon. The carbon prepared by first impregnation of VS with the 60 vol% H(3)PO(4) solution at 50 degrees C and by then carbonization of the resultant product at 400 degrees C for 2 h presents a higher ability to discolor the white wines. The action of this carbon is comparable to that shown by the commercial product. Both carbons possess a well-developed porosity in the macropore range.