Investigation of the Chemical and Biological Changes Identified with Sur Lie Treatment of Wine
The following summary is taken from the Technical Abstracts for the oral presentation given by Greg La Follette at the Annual Meeting of the American Society for Enology and Viticulture, 1991. This work comprises his Master’s Thesis research. During the 1989 and 1990 vintages, we examined wines from two commercial wineries. Sur lie wines (with extended yeast lees contact) were compared to wines racked immediately after fermentation. Sixty gallon stainless steel and oak barrels were used with the same juice to produce identical wines except for yeast contact and stirring. Samples taken monthly and at bottling revealed no differences in dissolved oxygen in the barrel, time for completion of malolactic fermentation cell viability, redox potential, viscosity, protein stability, fining requirements, pH and concentrations of protein, sulfur compounds and acetaldehyde. Results of diacetyl content and extent of browning were mixed. Racked wines were lower in phenol and total nitrogen concentrations. In the 1990 vintage, acetaldehyde was initially lower in sur lie wines; this difference diminished with time. Sensory analyses of bottled wines using the forced-comparison pair test showed no differences in oak aroma, while toast aroma was higher in sur lie wines. Results of butter and fruitiness as aroma descriptors depended on containers used: in oak, sur lies wines were less buttery and more fruity in aroma than racked wines; in stainless steel, racked wines were more fruity, with no differences in buttery aroma. With descriptive analysis, only apple and pineapple characteristics and spiciness were different. “Mouthfeel” components snowed no differences.