We get to hear from many winemakers looking to solve challenges as they arise and are always happy to help. None may be more taxing on one’s mental health than watching a wine fermentation slow, stall, and sometimes even get completely stuck. 

For high sugar wine fermentations, it can be helpful to analyze the amount of fructose compared to glucose in the fermentable sugars of the must. The ratio of glucose to fructose in grape must can significantly influence fermentation kinetics and wine quality. A high fructose-to-glucose ratio can lead to sluggish or stuck fermentations, as most wine yeast (Saccharomyces cerevisiae) typically prefers glucose.  

By carefully selecting a fructophilic yeast strain and optimizing fermentation conditions, winemakers can successfully ferment high-sugar, high-fructose musts and produce high-quality wines. These specialized fructophilic strains are the most effective way to deal with an imbalance in sugar created by high-fructose musts. Fructophilic strains can be good all-around fermenters, able to tackle other challenging fermentation conditions as well. 

Our first choice for fructophilic yeast and in challenging fermentation environments is Pinnacle™ Fructo, a superstar fermentation restarter, and overall strong fermenting yeast. Outside of being a stuck fermentation solution, there are several reasons to choose Pinnacle™ Fructo yeast: 

• Short Lag Time – A brief lag phase from pitch means less risk of other microorganisms dominating and contaminating your fermentation. 
• Cooler Fermentation Temperatures – It can handle cooler cellar and fermentation temperatures than other yeast strains. If you are unsure if your fermentation stalled due to temperature, Pinnacle™ Fructo works from 15-30°C (59-85°F.) 
• Low Foam – Additional energy isn’t required managing the foam cap a wine high in tannin or alcohol might create when it restarts. 
• Low Nitrogen Requirement – A stuck fermentation may be caused by a lack of nitrogen in the fermenter. These stalled fermentations often require the addition of yeast nutrient, best practice is to provide fermentation aid, but Pinnacle™ Fructo should not require a significant amount to restart, if at all. 

• High-Fructose Fermentation – A high-fructose environment may be caused by late-harvest grapes, botrytis-affected fruit, or the addition of sugar for sweet wines. Most typical yeast strains prefer glucose over fructose, which can lead to stuck or sluggish fermentations when only fructose remains. Pinnacle™ Fructo is fructophilic, and efficient at converting fructose, ensuring minimal residual sugar. 
• Improved Flavor in Sweet Wines – In sweet or dessert wines, where there may be a significant amount of fructose, Pinnacle™ Fructo can ensure a clean and controlled fermentation and contribute to the wine’s desired balance of sweetness, acidity, and alcohol while minimizing potential off-flavors associated with incomplete fermentations. 

• Good Under Stress – Pinnacle™ Fructo is more resilient in stressful fermentation environments, such as high sugar concentrations or extreme osmotic pressures. This makes it suitable for wines with high initial sugar levels, like ice wines or late-harvest wines, where glucose and fructose levels are elevated. 
• Completely Fermented Dry Wines – For winemakers aiming for a dry wine, residual fructose poses one of the greatest challenges, especially if the primary yeast strain cannot ferment it completely. Using Pinnacle™ Fructo yeast can help reduce or eliminate this residual sugar, creating a stable wine with less risk of re-fermentation in the bottle or spoilage due to unwanted microbial activity. 
• Compatibility in Mixed Fermentations– Pinnacle™ Fructo yeast can be used in combination with other yeast strains that are glucose-preferring. This can create a more complete fermentation process, where glucose-preferring strains first reduce the glucose levels, and then Pinnacle™ Fructo efficiently finish off the fructose, leading to a fully fermented wine. 

Pinnacle™ Fructo yeast is a stuck-fermentation Swiss-army knife, particularly useful when dealing with musts that have high fructose content. It can also help you achieve more consistent wine profiles, especially in wines where sugar content and fermentation completion are key factors. By ensuring efficient fructose utilization, Pinnacle™ Fructo yeast can both improve fermentation success and your overall wine quality. 

Available in 500g and 10kg sizes, get in touch with us today to give your wines the Pinnacle™ Fructo advantage! 

For more information on fructophilic fermentation we recommend Jason Mabbett’s excellent article “Fructophilic Yeasts – Consequences of Yeast Strain Selections” available here. 

Yeast Pinnacle Stuck Fermentation