Effect of Macerating Enzymes on Red Wine Aroma at Laboratory Scale:  Exogenous Addition or Expression by Transgenic Wine Yeasts

The effects of a Trichoderma longibrachiatum endoglucanase and an Aspergillus nidulans endoxylanase on the concentration of free and bound volatiles, color, and phenolics during maceration in red wine vinification has been studied. Two different approaches have been considered for the utilization of these enzymes: (i) direct addition of the enzymes to must and (ii) inoculation of must with recombinant wine yeasts overexpressing these activities. An experimental design based on a Taguchi orthogonal array was carried out in order to evaluate the effects of the enzymatic treatments. The data show that these fungal activities are able to increase the concentrations of free and glycosidically bound flavor compounds, color, and phenolics to similar or greater extents as compared to a commercial pectolytic enzyme preparation. The effects of the two different ways of addition of the enzymes were not always equivalent. These enzymes could be considered to be of potential application in the red wine maceration process. Keywords: Endoglucanase; endoxylanase; maceration; transgenic yeast; aroma precursors; wine