Complete Guide to Cider Fermentation Nutrition
Last Updated: 9/2022
Applies to: Cidermakers looking for more information on yeast nutrient requirements and product recommendations.
What Nutrients do Yeast Need?
What Nutrients are Present in Apples?
While apples contain nitrogen, vitamins and minerals, and survival factors, they do not contain them in levels that will support healthy fermentation. Most notably, apples have very low yeast assimilable nitrogen (YAN)1. YAN supplementation throughout fermentation is necessary for a healthy cider fermentation. Additionally, apple YAN will vary between cultivars and growing seasons1 but can also vary within a cultivar and growing season.
Apple YAN is composed of amino acids. Apple amino acid composition heavily favors a few amino acids (asparagine and phenylalanine) over all others2. While this has not been heavily researched, it is hypothesized that this unbalanced amino acid profile may lead to issues in fermentation kinetics especially when YAN is not properly supplemented1.
How Much YAN is Required for Fermentation?
The amount of supplementation required for a healthy fermentation depends on several factors:
Initial juice chemistry: Prior to fermentation, sugar content and YAN should both be measured. Higher sugar and lower YAN fermentations will both require higher levels of YAN supplementation. Initial YAN levels may be affected by:
Processing and storage conditions: Apples can be stored after harvest in modified atmosphere storage for long periods of time. Alternatively, juice may be pressed immediately and frozen or concentrated. All of these decisions will affect YAN. Even if you are very consistent with your sourcing, you may see YAN variability.
Native microflora activity: Native microflora will consume YAN as well as vitamins and minerals, even in healthy fruit and juices. The longer the juice sits prior to inoculation, the lower the YAN will be.
Dissolved oxygen: Nitrogen is captured faster by yeast in juices with higher oxygen content, therefore more YAN will be necessary to sustain yeast over the course of fermentation. This may be a factor in stored/transported juice or thawed juices as the dissolved oxygen content may be higher in those.
Fermentation temperature: Higher fermentation temperatures stimulate fermentation rate and yeast growth, thereby requiring more nitrogen than cooler fermentations.
Scott Laboratories offers three types of yeast nutrients:
Rehydration nutrients are added while rehydrating yeast. While they will contribute some nitrogen to a fermentation, rehydration nutrients should not be considered significant sources of YAN. Rather, they supply yeast with vitamins, minerals, and sterols. These compounds promote the development of healthy yeast that can withstand fermentation conditions. For example, sterols are incorporated into yeast cell membranes to improve their tolerance to increasing ethanol.
Fermentation nutrients supply the yeast with nitrogen (YAN). We recommend adding these nutrients to the juice at inoculation and again partway through fermentation. Supplementing YAN at the beginning of fermentation ensures that a sufficient yeast population to sustain fermentation will develop. Supplementing YAN during fermentation avoids yeast stress which may result in off-odor development and stuck/sluggish fermentations.
Yeast Derivative Nutrients
Yeast derivative nutrients are used for their ability protect positive sensory compounds and/or remove negative sensory compounds. While they will contribute some nitrogen to a fermentation, they should not be considered significant sources of YAN. Yeast derivative nutrients should be added either prior to inoculation or toward the end of fermentation. These nutrients are produced from specific strains of yeast that have been inactivated and then autolyzed (partially or fully).
They contribute compounds naturally found in or produced by yeast including:
• Glutathione and other peptides which have antioxidant effects
• Polysaccharides which can improve mouthfeel by reducing astringency and increasing volume
• Low levels of copper which can reduce sulfur off-odors
|Pre-Fermentation||Antioxidation||GLUTASTAR™ or OPTI-WHITE™||Yeast Derivative Nutrients|
|During Yeast Rehydration||Provide yeasts vitamins, minerals and sterols to|
promote healthy populations that can withstand
|GO-FERM PROTECT EVOLUTION™||Rehydration Nutrient|
|At Inoculation||Nourish yeast with amino acids for steady fermentation|
|FERMAID O™||Fermentation Nutrient|
|During Fermentation||Maintain steady fermentation rate and avoid off-odor|
|STIMULA CHARDONNAY™ or |
FERMAID O™ and/or FERMAID K™
|End of Fermentation||Enhance cider flavor profile||OPTI-WHITE™ or NOBLESSE™||Yeast Derivative Nutrients|
|Manage sulfur off-odors||REDULESS™||Yeast Derivative Nutrient|
|Scavenge oxygen to prevent oxidation||PURE-LEES™ LONGEVITY||Yeast Derivative Nutrient|
WHY WE RECOMMEND STAGED NUTRIENT ADDS
Our recommendation for optimal yeast nutrition includes adding nutrients at 2 or 3 time points. We recognize that production constraints may not be compatible with multiple nutrient additions. It is more important to sufficiently compensate for the juice’s nutrient deficiency than it is to achieve optimal addition timing. Understanding our justification for the timing of each nutrient addition may help you develop the best nutrient regime for your process:
Nutrients should always be added during the yeast rehydration phase to supply the often-deficient vitamins and minerals, sterols, and unsaturated fatty acids (survival factors). This first add can be achieved using GO-FERM PROTECT EVOLUTION.
Nutrients should be sufficient in juice at inoculation so that yeast have enough nitrogen to grow and multiply. This is important as the number of cells will drive fermentation rate. If the juice has enough YAN to begin fermentation, then a nitrogen addition may not be necessary. If the juice is deficient, FERMAID O may be added.
Nutrients should be added during fermentation (at or around 1/3 sugar depletion) to replenish YAN levels. Yeast quickly utilize YAN present at inoculation and can encounter deficit conditions midway through fermentation. Adding nutrients like FERMAID O, FERMAID K™, or STIMULA CHARDONNAY at 1/3 sugar depletion avoids yeast stress so that sugar uptake can continue, fermentation rate remains steady, and the yeast can produce desirable aroma compounds.
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1. Stewart, A. C., Ma, S., Peck, G. M., McGuire, M. N., Boudreau, T. F., & O’Keefe, S. F. (2018). Yeast Assimilable Nitrogen and Cider Fermentation. Scott Laboratories Cider Handbook.
2. Ma, S., Neilson, A. P., Lahne, J., Peck, G. M., O’Keefe, S. F., & Stewart, A. C. (2018). Free amino acid composition of apple juices with potential for cider making as determined by UPLC-PDA. Journal of the Institute of Brewing, 124(4), 467–476. https://doi.org/10.1002/jib.51...