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68 WINES&VINES May 2018 GRAPEGROWING PRACTICAL WINERY & VINEYARD N ew Zealand winegrowers use me- chanical harvesting as a norm. This is probably out of necessity, however it is by far the harvesting method delivering the highest concentration of thiols. This is contradictory to what has been believed for years to be best practice when producing top quality wines. Research studies comparing harvesting methods such as hand-picked with whole bunch pressing, hand-picked with crushing and destemming and machine harvesting showed an increase in thiol concentration as the "roughness" of the method increased. 11 This observation falls in line with the scientific explanation involving oxygen, enzymes and C6 compounds together with a sulfur donor. An actual increase of some C6 compounds when comparing hand-picked grapes to machine-harvested grapes has been ob- served. With greater maceration (longer skin contact) of the fruit and greater enzyme activity, the levels of the C6 compounds in- creased. The addition of maceration enzyme and sufficient time given for the reaction to occur can increase the thiols formed during the process. Wine producers can mimic the effect that mechanical harvesting has on grape berries. Some of these tools are listed below, but the fundamental aspect would be to cause some berry damage with sufficient protection to avoid too much oxidation. Presence of antioxidants When it comes to volatile thiols the importance of the presence of antioxidants cannot be overstated. The -SH group of the volatile thiols makes these compounds extremely susceptible to oxidation. It is therefore important to pro- tect the wine from oxygen exposure and ensure sufficient presence of antioxidants such as Preserving and Increasing Thiols Adjusting Sauvignon Blanc aroma and flavor complexity By Carien Coetzee CONCANNON VINEYARD KEY POINTS This article aims to share information and insights obtained from a visit to Marlbor- ough, New Zealand, in 2016. Industry work- shops on Sauvignon Blanc production were hosted by the New Zealand Society for Viti- culture & Oenology where researchers and producers shared knowledge and ideas on traditional and novel methods of producing top-quality Sauvignon Blanc wines. Volatile thiols were the focal point of many discussions. This is part two of a two-part report and it investigates newest research and findings around these odorous compounds. Much of the work mentioned was presented by Paul Kilmartin from the Wine Science Program at the University of Auckland in a presentation, "Thiols in Sauvignon Blanc." Research studies in New Zealand showed an increase in thiol concentration as the "roughness" of the harvesting method increased.