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Pre-Fermentation Analyses

Pre-Fermentation Analyses. VWT 172 Bryan Avila. Overview. Process overview Brix by Hydrometer Acidity pH and TA (Completed during Maturity Assessment Module) Yeast Assimilable Nitrogen (YAN) Ammonia(NH3) alpha amino nitrogen (AAN). Pre-Fermentation.

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Pre-Fermentation Analyses

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  1. Pre-Fermentation Analyses VWT 172 Bryan Avila

  2. Overview • Process overview • Brix by Hydrometer • Acidity • pH and TA (Completed during Maturity Assessment Module) • Yeast Assimilable Nitrogen (YAN) • Ammonia(NH3) • alpha amino nitrogen (AAN)

  3. Pre-Fermentation All of the processes involved with bringing the fruit in from the vineyard and manipulating the clusters and berries into the desired state Pull juice samples for sugar, acid and Nitrogen content NOTE – Chemical analysis are generally pulled to measure chemistry that, if uncorrected, my cause significant quality or winestyle defects.

  4. Process Overview Weigh fruit Destem/Crush Add SO2 Take juice sample for analysis Adjust acid and/or brix if needed

  5. Pre-Fermentation Water Addition Brix, pH, TA Additions: - Acid - Tannin - Enzymes Sulfur Dioxide Brix Fermentation Time (Days)

  6. Pre-Fermentation AnalysisWhy do we care about these? • Brix – Sugar Concentration • By Refrac – Allows for check using same method used as with grape sampling • By Hydrometer – Initial sugar measurement • pH – Number of protons in solution – Assess risk level • TA – Titratible Acidity - used to make acid additions • YAN – Yeast Assimilable Nitrogen (NH3 + AAN) – Measure Nitrogen for precise additions of DAP and Complex nutrients • VA – Volatile Acidity – Indicator of spoilage • Malic Acid – may allow for additional acid addition • Microbiological Analysis – assess risk of microbial spoilage

  7. Must Adjustments Based on chemical and sensory analyses the following decisions are routinely made based on these analyses: Sugar Low sugar must may require a concentration addition to elevate the potential alcohol High sugar musts may require a water addition or a “de-alc” after fermentation Acid additions Low acid conditions may warrant an acid addition Nitrogen additions (YAN) Low Nitrogen levels are identified and add rates are calculated for addition prior to and during fermentation. DAP and Complex nutrients are added just prior to inoculation Once the processing is complete and additives are made your tank is ready for inoculation The last step of Pre-fermentation includes the YAN adjustment

  8. Table 1: Typical YAN Levels Required for Good Fermentations

  9. Must Analysis

  10. Hydrometry A hydrometer measures the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water. Sugar equates to over 90% of the soluable solids in in juice allowing for physical measurement that can be well correlated to sugar concentration. Measures % dissolved solids. THEY MUST BE DISSOLVED TO AFFECT LIQUID DENSITY. Measured in °Brix which is equal to grams per 100ml (g/100ml) Example 20 °Brix = 20% = 20 g/100mL = 200 g/L Alcohol is less dense than water and the the accuracy of the Brix measurement decreases as the fermentation progresses

  11. Nitrogen Saccharomyces needs sugar and nitrogen to complete a fermentation Required for yeast growth and development (ie. Amino acids, nucleic acids, etc) Often is depleted prior to fermentation and thus additions are necessary When alpha amino nitrogens are depleted the yeast switch over to sulfur based amino acids which causes hydrogen sulfide (rotten egg smell) Untreated sulfides will eventually progress into mercaptains which are also-off aromas

  12. Nitrogen A lack of Nitrogen may even lead to sluggish or stuck fermentations You should be prepared to add Nitrogen at the start of fermentation to prevent these problems. The total nitrogen in a fermentation is measured by the sum of the alpha-amino nitrogen plus ammonia. (AAN + NH3 = YAN)

  13. Nitrogen If you want to avoid problems, you must be prepared to add nitrogen to your fermentations. Additions are often made either right before or after inoculation and once the fermentation reaches log phase. General Rule of Thumb – Do not add nitrogen below 12 brix to treat sulfides (use Copper Sulfate)

  14. Nitrogen Adjustment 100 ppm addition of DAP is about a 20 ppm increase in YAN 2#/1000 gal (1 gram/ gallon) of DAP is approximately a 50ppm increase in YAN 2# per 1000 gal of Fermaid K will yield an approximate increase of 25ppm YAN. (This is the max addition which is limited by Thiamin) 2 Additions are usually preferred

  15. Pre-Fermentation Brix Nitrogen Additions Time (Days)

  16. Alpha Amino Nitrogen by OPA AAN is the same as PAN or primary amino nitrogen Often called an enzymatic analysis but is actually a chemical analysis but the procedure is very similar Omits the measurement of proline which the yeast do not use unlike with the Formol titration

  17. OPA Reaction Amino nitrogen + N-acetyl-L-cysteine + o-phthaldehyde isoindole derivative

  18. Ammonia May use a probe similar to a pH probe or enzymatic method The ammonia number is also known as the free ammonia nitrogen (FAN)

  19. END Please Note - pH and TA were covered during week 3 and VA and Malic Acid will be covered later.

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