Impacts of natural yield variance on wine composition and sensory quality of Riesling and Cabernet franc

Abstract

This study investigated impacts of naturally-varying yields on Riesling and Cabernet Franc wine composition and sensory attributes. Sites were chosen based on location within 5 Vintners Quality Alliance Ontario sub-appellations. A grid-based sampling pattern was developed for each vineyard block with a sentinel vine chosen for data collection at each grid intersection (72-84 sentinel vines per site). Cultural practices, including pruning and canopy management were consistent within each vineyard block. Vine yields were divided into categories of “low”, “medium”, and “high” (LY, MY, HY) at harvest. Wines were analyzed for pH and titratable acidity (TA) and Cabernet franc wines were also analyzed for color hue and intensity, anthocyanins, and total phenols. All replicate wines were initially subjected to a multidimensional sorting (MDS) task to confirm sensory differences between wines produced from different yield categories and between different sites. All wines were then subjected to descriptive analysis (DA). LY Cabernet Franc wines had higher color, anthocyanins and phenols. Natural yield variance had little to no effect on pH and TA for both Cabernet franc and Riesling. MDS effectively determined differences between HY and LY wines. Five aroma and 8 flavor attributes for Riesling and 3 aroma and 6 flavor attributes for Cabernet Franc differed between yield categories in the DA. HY Riesling wines were associated with lower intensity of stone fruit attributes and higher mineral or floral. HY Cabernet Franc vines produced wines with higher bell pepper and less fruit characteristics. Sub-appellations had an effect on the wine sensory profile. Riesling wines from Lincoln Lakeshore (north) and Niagara Lakeshore were associated with mineral attributes, Four Mile Creek with apple/pear, and St. Davids Bench, Beamsville Bench and Lincoln Lakeshore (south) with stone fruit and citrus. Cabernet Franc wines from Beamsville Bench and the Four Mile Creek were associated with bell pepper, Lincoln Lakeshore (north) with earthy, and Lincoln Lakeshore (south) with cooked fruit. Increasing yield in Cabernet Franc reduced concentration of sec-butyl methoxypyrazine (SBMP) and increased isobutylmethoxypyrazine (IBMP). IBMP increased with increased crop level in 3 vineyards (Beamsville Bench, Lincoln Lakeshore north, Lincoln Lakeshore south).