Cider making is both an art and a science. He shares some valuable insights into how yeast selection and nutrition profoundly impact the final product. This blog post provides valuable insights into how yeast selection and nutrition profoundly impact the final product, as well as explores some key takeaways and provides practical knowledge for cider enthusiasts and producers alike.
The Foundation: Yeast Selection
After pressing the juice, the journey continues with yeast. Deciding how your cider is fermented and yeast strain choice is crucial, as it dictates the cider’s style and flavour profile. Factors to consider include desired flavour characteristics, flocculation (yeast settling) behaviour, attenuation (sugar conversion), and how the cider will be conditioned (keg, bottle, etc.).
- Spontaneous fermentations: Relying on the wild yeast and bacteria present on the fruit, can yield ciders of remarkable complexity and unique character. While this approach celebrates the terroir and inherent microbes, understanding their dynamics and needs is crucial for guiding the fermentation towards a desired outcome. To ensure complete fermentation and prevent potential spoilage, it’s sometimes beneficial to introduce a selected, neutral yeast strain or to control the malolactic fermentation with a known bacteria towards the end, meaning that residual nutrients are consumed that could otherwise feed unwanted microorganisms which would affect the shelf life of your cider.
- Dry vs. Fresh Yeast: Fresh yeast offers a wider variety of strains and potentially shorter lag times (the time it takes for yeast to become active) and can be repitched, but it has a shorter shelf life and requires careful storage. Dry yeast, on the other hand, is easier to store and transport, with a longer shelf life, though it may have less strain variety and potentially longer lag times.
- Strain Diversity: The world of yeast is diverse, with various species and hybrid isolates contributing unique characteristics to cider. Understanding the origin and behaviour of different strains allows cider makers to fine-tune their creations.
- The Fermentation Process: It’s crucial to recognize that fermentation is far more intricate than simply converting sugar into alcohol. Yeast cells are dynamic metabolic factories, orchestrating a symphony of biochemical reactions. Beyond ethanol production, they actively process nutrients and respond to their environment, yielding a diverse array of flavour and aroma compounds that contribute to the cider’s unique character.
Nourishing the Yeast: The Importance of Nutrition
Yeast performance is heavily influenced by its environment, and nutrition plays a vital role.
- Essential Nutrients: Yeast requires a balanced “diet” to thrive, including sugars (from apples), nitrogen, lipids, sterols, vitamins, and minerals. These nutrients are crucial for various aspects of yeast health and function. Products such as Yeast Vit Cider and Fermaid O can help you achieve this.
- Why Nutrition Matters: Proper nutrition ensures consistent fermentation, prevents stuck fermentations (where yeast stops prematurely), and optimises flavour development.
- Nitrogen’s Role: Nitrogen, particularly Yeast Assimilable Nitrogen (YAN), is essential for yeast cell function, impacting both performance and flavour. If you’d like to know how much you have available, please send a sample of your juice to our lab and we can advise on levels and requirements.
- Avoiding Imbalances: Simply adding one nutrient, like DAP (diammonium phosphate), can lead to imbalances and problems such as decreased yeast viability, off-flavours, SO2 issues, and even stuck fermentations. The use of speciaised nutrient blends mean you can get the right balance of different nitrogen sources exactly where they’re needed.
Optimising Fermentation Conditions
Beyond nutrition, other factors influence yeast performance:
- Temperature: Yeast has a specific temperature range for optimal fermentation. Temperature fluctuations can stress the yeast, affecting fermentation speed and flavour profiles. It is worth considering when/where the fermentations take place to avoid any extremes in temperature that would cause yeast stress.
- Oxygen: Oxygen is needed for cell membrane health and growth in initial stages of fermentation but should be limited once fermentation has kicked off. This ensures a healthy fermentation and stops too many yeast cells from being produced which can cause yeast related off-flavours also.
Finishing Touches
- Sulphur Dioxide (SO2): SO2 is a crucial tool for controlling unwanted microorganisms and preventing oxidation. However, precise dosage is essential. KMS solution is a great product to use in this situation, please check your pH as the amount of free SO2 necessary to effectively protect cider is influenced by its pH; higher pH levels necessitate increased amounts of free SO2. It is important to note that different yeast strains can also produce different amounts of sulphur. If there is too much sulphur in the final product giving off-flavours/aromas, it can be reduced using Zetolite 63 (Copper). Our lab can also help with sulphur analysis and recommendations – please send a sample if you would like this analysed.
- Clarification: Achieving clarity is important for cider presentation. Natural fining agents like Naturo F, a biodegradable & food-grade finings solution, consisting of chitosan (a polysaccharide derived from the cell walls of fungi, notably mushrooms) can effectively clarify cider while preserving its quality.
If you have any question or would like more information, get in touch with our tech team by emailing technical@murphyandson.co.uk