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78 WINES&VINES April 2018 GRAPEGROWING PRACTICAL WINERY & VINEYARD S ulfur-containing compounds in wine include a wide range of typically very powerful aromatic molecules. These compounds are referred to as mer- captans or volatile thiols, both indicating com- pounds containing the sulfhydryl group (-SH). Wine industry and research circles have grown accustomed to some of these generic terms being used for specific compounds. For example, the term "volatile thiols" (sometimes called "varietal thiols") immedi- ately sparks a preconceived reference to fruity and tropical aromas, while "mercaptans" generally refer to compounds contributing to the reductive odors reminiscent of cabbage and burnt match. In some cases, the term "sulfur" is used to describe either of these odor groups or even refer to the typical "chemical" smell when sulfur dioxide is picked up sensorially and could cause confu- sion during evaluations. Volatile thiols in wine are important com- pounds contributing to the varietal character of wine made from several cultivars, notably Sauvignon Blanc. These sulfur-containing compounds are one of the main reasons for the success observed in Sauvignon Blanc produced in Marlborough, New Zealand, with concentra- tions soaring to levels only imagined in most wine-producing countries. They are not limited to one grape variety, and significant contributions also have been observed in Chenin Blanc, Riesling, Colombard, Semillon, Cabernet Sauvignon and Merlot. However, Sauvignon Blanc has enjoyed the most attention when it comes to these potent molecules, due to the fact that large quantities can be found in wines produced from this cultivar. Research conducted at Stellenbosch Uni- versity in South Africa involved screening South African Chenin Blanc wines to inves- tigate the impact of volatile thiols on the sensory characteristics of this variety. Pre- liminary results look promising and could affect how this variety is handled in the vineyard and cellar. Research of volatile thiols has been a hot topic in the past 10 years. Studies conducted at various universi- ties around the globe have only recently clarified formation and stability of the aro- matic compounds. One reason for this could be difficulty surrounding the analysis of volatile thiols. Volatile thiols are present in wine at ng/L (parts per trillion), which complicates the quantification significantly. Grape-Derived Fruity Volatile Thiols Adjusting Sauvignon Blanc aroma and flavor complexity By Carien Coetzee KEY POINTS The New Zealand Society for Viticulture & Oenology hosted industry workshops about Sauvignon Blanc production in Marlbor- ough, New Zealand, in 2016. Researchers and producers shared knowledge and ideas on traditional and novel methods of produc- ing top-quality Sauvignon Blanc wines. Volatile thiols were the focal point of many discussions. Much of the work mentioned was presented by Paul Kilmartin from the Wine Science Program at the University of Auckland. This article is the first installment in a two- part series and will cover the origin of the volatile thiols. Part two will investigate the newest research and findings around these odorous compounds. Volatile thiols in Sauvignon Blanc wines begin in the grapes and were the focal point of discussions at in- dustry workshops in New Zealand.