Recovery of winery by-products in the Douro Demarcated Region: Production of calcium tartrate and grape pigments

Abstract

The Douro Demarcated Region includes 39,000 hectares of vineyards in northern Portugal and is responsible for the annual production of over 50 thousand tons of winery by-products. These by-products are subjected to distillation to recover the ethanol, after which only the wine lees are extracted with an acid solution, intending the production of calcium tartrate. This study characterizes the winery by-products of the region with regard to its potential production (from both grape pomace and wine lees) of calcium tartrate and grape pigments. The quantification of potassium bitartrate (the raw material for calcium tartrate) and total anthocyanins was performed using spectrophotometric methods on winery by-products sampled at 16 of the major wineries of the region. These wineries are responsible for the production of half the winery wastes in the region. Results indicate values ranging from 100 to 150 kg/t (wine lees) and 50 to 75 kg/t (grape pomace) with respect to the potential production of calcium tartrate. The average figures for the grape pigment vary from 12 kg/t (red wine lees) to 9 kg/t (red grape pomace), the final product being in the form of a liquid concentrate with 30 g of pigments per kilogram of solution.