A Novel process for pinot noir wine making

摘要

Pinot noir grapes offer a challenge for wine makers due to the variety’s unusual tannin distribution and non-acylated (colourless) anthocyanins. Initially, two scoping studies using replicated ‘French Press’ microvinification of Pinot noir must were undertaken and wines were evaluated for seven phenolic measures quantified by modified Somers analysis using UV-visible spectrophotometry and chemometrics (total phenolics, total pigment, anthocyanin, tannin, non-bleachable pigment, colour density, hue). The scoping studies established that yeast strain choice and maceration approach could significantly influence the concentration of phenolics in Pinot noir wine.udA novel maceration process, microwave maceration, which was included in the scoping study was associated with significantly higher concentration of total phenolics, anthocyanin, tannin and non-bleachable pigment in wines at 18 months bottle age, compared with control wines that had been fermented on skins for a comparable period (usually seven or eight days). Microwave maceration involved heating Pinot noir must to 70ºC using a domestic 1.5 kW microwave oven. Must was held at that temperature for a ‘hold time’ period to allow for time/temperature mediated phenolic extraction, before being cooled to ~27ºC for inoculation and fermentation under controlled conditions.udThe rapid and effective phenolic extraction from microwave maceration of Pinot noir grape must allowed several novel approaches to winemaking. For example, microwave macerated must with one hour of hold time was pressed off skins and fermented as an ‘enriched juice’. Early press-off microwave maceration wines were equivalent to control wine that had been fermented on skins for most phenolic parameters, but were significantly higher in fourteen out of sixteen aroma compounds examined by GCMS. For example, the microwave treatment wines were generally four to six-fold higher for the acetates examined, and two-fold higher for most of the ethyl esters examined. Microwave maceration was effective for sanitation of Pinot noir grape must and reduced background yeast to≤100 cfu/mL by plating to Wallerstein Laboratories Nutrient agar, which was more effective than standard must sanitation by application of 50 mg/L sulphur dioxide in the form of potassium metabisulfite solution (2x104 cfu/mL).udDue to the sanitation effect of microwave maceration, must did not require application of sulphur dioxide at crushing to suppress background yeast and bacteria. Sulfur dioxide and high fermentation temperatures are stressors which have been shown to inhibit malo-lactic fermentation in red wine fermentation. The rapid extraction of phenolics by microwave maceration prior to alcoholic fermentation, offset the need for high fermentation temperature (eg. 30ºC) and this, coupled with the absence of sulphur dioxide, allowed co-inoculation of yeast and malo-lactic bacterial cultures for simultaneous alcoholic and malo-lactic fermentation. Early press-off microwave macerated Pinot noir must inoculated in this way finished alcoholic and malo-lactic fermentation within 17 days demonstrating the possibility of highly efficient red wine making from this novel process.ududChapter 7, Wine phenolic and aroma outcomes from the application of Controlled Phenolic Release to Pinot noir must, was published in the Proceedings of the 16th Australian Wine Industry Technical Conference (July 2013, Sydney, Australia).