By Kevin Elder and Elizabeth Higley, Windsor Run Cellars
Summary
Stabulation has been shown to increase the thiol content in some wines by extracting more thiol precursors into the juice. Seyval Blanc is a hybrid varietal that is often dominated by thiol aromas similar to New Zealand Sauvignon Blanc. In this study Seyval Blanc was stabulated for for five days In a triangle test 28 out of 51 panelists correctly chose the different wine indicating the wines were significantly different (p 0.001). Of the panelists that correctly chose the different wine 18 preferred the stabulated wine compared to 7 that preferred the control.
Introduction
Stabulation is a winemaking process where the prefermentation juice lees are stirred periodically for several days with the intent of extracting more aromatic precursors from the juice lees. This process is often done by holding the freshly pressed juice at very cold temperatures to inhibit microbial activity and mixing is usually done by bubbling inert gas through the tank. Stabulation is thought to extract more of the odorless thiol precursors into the juice which is then racked off of the juice lees and fermented. The fermentation converts the precursors into aromatic thiols with aromas of grapefruit, boxwood and guava. The purpose of this experiment was to see if stabulation could increase these aromas in Seyval Blanc.
Methods
On August 10, 2022 5.96 tons of Seyval Blanc was hand-harvested into half-ton bins. Cinn-Free enzyme was added directly to fruit at a rate of 20 ml/Ton. Alternating bins were separated into two lots for separate processing with the intent of reducing variation due to fruit location within the block. For both lots fruit was destemmed, not crushed, and pumped into a bladder press. The two lots were pressed separately in a sequential program ending with a maximum pressure of 1.2 bar. Lafazyme Thiols (6g/hL) and 25 ppm SO2 was added to the press pan for both lots. The control tank was cold settled at 50 F overnight and then racked. The stabulation tank was chilled to 42 F and mixed twice a day for five days. Tank was mixed by nitrogen gas vigorously bubbled in at the bottom valve for about two minutes in the morning and two minutes in the afternoon. After five days of stabulation the tank was allowed to warm to 59 F and settle for two days before being racked.
Both control and stabulation tanks were inoculated immediately after racking with QA23 (25 g/hL) rehydrated with GoFerm Protect Evolution (30 g/hL) and allowed to ferment at 59 F. The following additions were made to both tanks: chaptalization to 19 Brix, Glutastar (30 g/hL), FT Blanc Soft (6 g/hL), Fermobent (150 g/hL), nutrient additions to achieve 200 ppm YAN. Upon completion of fermentation wines were racked and 60 ppm SO2 was added.
Sensory analysis was completed by a panel of 51 wine industry professionals at the 2023 North Carolina Winegrower’s Association annual conference. A triangle test was conducted where two of the glasses contained the same wine and one contained a different wine. The panelists were presented with three pre-poured glasses. The glasses were coded with random three digit codes and the order was randomized between panelists. Panelists were asked which wine was different as well as which wine did they prefer and why did they prefer it.
Results
In-house analysis showed that stabulation increased juice pH from 3.13 to 3.26 (Table 1). In the triangle test 28 out of 51 panelists correctly chose the different wine indicating the wines were significantly different (p 0.001). Of the panelists that correctly chose the different wine 18 preferred the stabulated wine, 7 preferred the control and 3 made no indication. Panelists that liked the stabulated wine generally remarked that they liked the aroma better and preferred the lower acidity. Panelists that preferred the control generally liked the higher acidity.
