The effect of early leaf pulling on thiol production in an Oregon Sauvignon Blanc (2018)

Chemeketa Community College, Scott Dwyer

Thiols have become a defining characteristic of aromatic Sauvignon Blanc wines. Early defoliation in the fruit zone has been shown to increase thiol production in South African Sauvignon Blanc (Šuklje et al 2104). In this study, leaves were removed from the east side of the fruit zone immediately after fruit set. Control rows had no leaf pulling. Resulting wines showed no differences in major chemistry, however wines with leaves pulled had lower concentration of thiols. Sensory analysis of resulting wines showed higher thiol intensity in control wines, with these wines also scoring significantly higher for aromatic intensity and acidity.

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The Impact of Increased Sulfur Dioxide at Crush on Color and Tannin Extraction (2017)

High concentrations of sulfur dioxide at crush can enhance color extraction during maceration. This study examines the impact of high levels of sulfur dioxide at crush on color and phenolic extraction. Pinot noir from a single vineyard block was sorted, destemmed, and divided into 4 T bins. The T bins received either 50ppm, 100ppm, 150ppm, or 200ppm sulfur dioxide at crush. All other treatments between wines were identical. 150ppm and 200ppm sulfur dioxide seemed to induce a slightly longer lag phase relative to lower levels of sulfur dioxide, but otherwise fermentation kinetics were similar. Wine chemistry was similar between treatments, except that TA and lactic acid decreased slightly with increasing levels of sulfur dioxide. Total, free, and molecular sulfur dioxide increased with increasing concentrations added at crush. Color intensity, anthocyanins, catechin, epicatechin, and tannin all seemed to increase as well from increasing sulfur dioxide usage. Overall, lower rates of sulfur dioxide tended to have higher Fruit Intensity. 100ppm of sulfur dioxide had a strong tendency for the highest Fruit Intensity and lowest Herbaceous/Green character. Body tended to be higher at 100ppm as well. Higher rates of sulfur dioxide addition (above 100ppm) tended to increase Astringency. The perception of Acidity may have been increased by higher sulfur dioxide levels as well. The most preferred wine was the wine produced with 100ppm of sulfur dioxide. More studies should be performed to evaluate the use of sulfur dioxide at crush, particularly with other grape varieties.

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