by Courtney Llewellyn
The first thought for a lot of people when it comes to cider is apples. But yeast should be high on that list too. Different yeast strains can fundamentally change how the finished product can come out, and understanding the importance of yeast selection for cider makers is critical. Fermentis, part of a worldwide company that focuses on all aspects of fermentation, recently presented its Fermentis Academy webinar on the diversity of yeast strains and fermentation conditions for different cider styles.
“There is a huge diversity of ciders, and that is linked to a huge diversity of substrates,” explained Anne Flesch, Fermentis regional sales manager, Western North America. It starts with cider apples, which can be sweet, bittersweet, bittersharp or sharp, and which differ in ratios of tannins to acid.
Fermented ciders start sweet, like the French style (about 5% ABV, fermented at low temperatures), then move up to dry ciders, and then American/English-style (with 7.5% – 8.5% ABV, fermented at a medium temperature). High gravity ciders come last (at 12.5% – 18% ABV, fermented at high temps).
“Why is yeast choice important?” Flesch asked. “The wine industry realized it first, then beer, and now it’s coming to cider. Depending on the yeast you use, it can release different aromas that come directly from apples. You want to make sure the characteristics match your cider style.” Yeast can influence fruity and acidity profiles, roundness and mouthfeel.
The variety of apple you use is important. Different sugars affect apple juice and fermentation in different ways. For example, the more malic acid, tannins, sugar and fructose there are, the more difficult the conditions are for the yeast. Yeast available nitrogen (YAN), pH, yeast pitching rate and fermentation temperature are also choices that may affect cider making.
What criteria should you consider for yeast selection? Flesch noted the following:
- For sweet cider production, with fermentation temperatures between 46º – 59º F, a low temp-resistant yeast and one that is sulfur dioxide (SO2) resistant, since fresh apples must be stabilized with SO2
- For dry/high gravity ciders, when sugar content is up to 70% fructose, you want a “fructophilic” yeast (one that “eats” fructose). Since YAN could be low, you need a yeast with low nitrogen requirements. And since ABV is higher in these style, you want a yeast that is high ABV and low pH resistant.
- For all types of cider, you want low SO2 production/combination, low undesirable sulfur compound production, low acetic acid production and a positive aromatic profile/sensory analysis.
Fermentis recently trialed four different yeast strains selected on their technical and aromatic criteria (SafCider AB-1, AC-4, AS-2 and TF-6), using four cider recipes with various raw material and fermentation conditions (French sweet, English dry, French dry and high gravity/American). Four criteria were analyzed, evaluating the robustness of the fermentation and the resulting cider. They looked at kinetics, the final ABV and residual sugar; the analytical profile; the aromatic profile; and the sensory analysis.
To see the full trial results, click here for the slides from the presentation.
“Yeast selection and fermentation management is crucial depending on the cider maker’s target,” Flesch concluded. Their trials showed yeast strains may have a huge impact on cider profiles not only in terms of fermentation performance and analytics but also from a sensory perception standpoint. Gravity, temperature and nutrition are also important drivers of the fermentation and aromas.