Microwave maceration of Pinot noir: phenolically equivalent, aromatically distinct
Carew, ALJ and Lloyd, N and Close, DC and Dambergs, RG, Microwave maceration of Pinot noir: phenolically equivalent, aromatically distinct, 15th Australian Wine Industry Technical Conference 2013, 13-18 July 2013, Sydney, Australia (2013) [Conference Extract]
Approximately 40% of Pinot noir grape must is grape solids which are pressed off as marc, post-fermentation. Rapid phenolic extraction by microwave maceration offers an alternative to alcoholic fermentation of Pinot noir on pomace. In this independently replicated trial, 1kg lots of Pinot noir grape must were microwave macerated and pressed off after approximately three hours total contact time. Juice from microwave maceration was inoculated for AF and later comparison with control wine that was fermented on pomace for 7 days. Analysis of wines by UV-visible spectrophotometry at 210 days post-harvest (6 months bottle age) showed that microwave macerated wines were equivalent to control wines for mean concentration of: total phenolics, total pigment, anthocyanin, total tannin, colour density and hue, and microwave wines were higher in mean pigmented tannin than control wines (0.46AU and 0.31AU, respectively). Non-targeted profiling analysis of volatile aroma compounds was carried out by GCMS at 320 days post-harvest (10 months bottle age). Principal component analysis (PCA) showed that control and microwave wines were distinct from each other on the basis of 16 aroma compounds, with 80% of the separation between the two maceration treatment wines explained by PC1. Loadings analysis indicated that separation on PC1 was driven by concentration of: 2&3-methylbutanol (nail polish aroma), 2-methylpropanol (fusel, spiritous aroma) and ethyl octanoate (red cherry, raspberry aroma). We showed that microwave maceration may reduce constraints on winery capacity by eliminating pomace during fermentation, provide greater control over red wine phenolics and generate wines with distinct aroma qualities.