Two methods of port vinification: a comparison of changes during fermentation and of characteristics of the wines

A traditional lagar (stone trough) fermentation, with crushing by treading, was compared with fermentation in a tank with mechanical crushing. For the tank fermentation, pigment extraction was increased by pumping juice drawn from the bottom of the tank through a spray head at the top of the tank. Yeast growth, sugar depletion, ethanol formation, and changes in amino acid composition were monitored during the two kinds of fermentation. No marked differences in these fermentation characteristics were found between the lager and tank systems. The effect on the quality of the end product was assessed by color analysis and sensory assessments of the wine during maturation. The results showed initial differences in pigment extraction and significant differences in sensory attributes; but as the wine matured over three years, this difference in sensory quality became insignificant. Hence, the sensory quality of the finished wines did not depend on the method of production.